Skocz do pozycji: 1.

Tytuł:

Rotating Rayleigh-Benard convection

Autorzy:

Majchrowski, W.
Tuliszka-Sznitko, E.

Powiązania:

https://bibliotekanauki.pl/articles/1943236.pdf

Data publikacji:

2008

Wydawca:

Politechnika Gdańska

Tematy:

DNS
Rayleigh-Benard convection

Opis:

In the this paper our results on the natural convection in an enclosed rotating cavity are presented. We have focused our attention on the influence of the Rayleigh and Taylor numbers on the flow structure. DNS computations have been performed for the geometry of aspect ratio L=9 and curvature parameter Rm=1.5.

Źródło:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2008, 12, 3-4; 267-272
1428-6394

Pojawia się w:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 2.

Tytuł:

Thermal convection in a ferromagnetic fluid layer with magnetic field dependent viscosity: a correction applied

Autorzy:

Prakash, J.
Kumar, R.
Kumari, K.

Powiązania:

https://bibliotekanauki.pl/articles/178325.pdf

Data publikacji:

2017

Wydawca:

Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej

Tematy:

ferromagnetic convection
magnetic field dependent viscosity
stationary convection
Rayleigh number

Opis:

The effect of magnetic field dependent (MFD) viscosity on thermal convection in a horizontal ferromagnetic fluid layer has been investigated numerically. A correction is applied to Sunil et al. [24] which is very important in order to predict the correct behavior of MFD viscosity. Linear stability analysis has been carried out for stationary convection. The MFD viscosity parameter δ as well as the measure of nonlinearity of magnetization M₃, both have a stabilizing effect on the system. Numerical results are also obtained for large values of magnetic parameter M₁ and predicted graphically.

Źródło:

Studia Geotechnica et Mechanica; 2017, 39, 3; 39-46
0137-6365
2083-831X

Pojawia się w:

Studia Geotechnica et Mechanica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 3.

Tytuł:

Natural and mixed convection of a nanofluid in porous cavities: critical analysis using buongiorno’s model

Autorzy:

Zahmatkesh, Iman
Habibi, Mohammad Reza

Powiązania:

https://bibliotekanauki.pl/articles/279435.pdf

Data publikacji:

2019

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

natural convection
mixed convection
nanofluid
porous media
Buongiorno’s model

Opis:

In this paper, Buongiorno’s mathematical model is adopted to simulate both natural convection and mixed convection of a nanofluid in square porous cavities. The model takes into account the Brownian diffusion and thermophoresis effects. Both constant and variable temperatures are prescribed at the side walls while the remaining walls are maintained adiabatic. Moreover, all boundaries are assumed to be impermeable to the base fluid and the nanoparticles. The governing equations are transformed to a form of dimensionless equations and then solved numerically using the finite-volume method. Thereafter, effects of the Brownian diffusion parameter, the thermophoresis number, and the buoyancy ratio on the flow strength and the average Nusselt number as well as distributions of isocontours of the stream function, temperature, and nanoparticles fraction are presented and discussed.

Źródło:

Journal of Theoretical and Applied Mechanics; 2019, 57, 1; 221-233
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 4.

Tytuł:

Rayleigh-Bénard convection in an elastico-viscous Walters’ (model B’) nanofluid layer

Autorzy:

Rana, G. C.
Chand, R.

Powiązania:

https://bibliotekanauki.pl/articles/202036.pdf

Data publikacji:

2015

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

nanofluid
oscillatory convection
Rayleigh-Benard convection
viscoelasticity
Walters' (model B') fluid
oscylacyjna konwekcyjna
komórki Bénarda
lepkosprężystość

Opis:

In this study, the onset of convection in an elastico-viscous Walters’ (model B’) nanofluid horizontal layer heated from below is considered. The Walters’ (model B’) fluid model is employed to describe the rheological behavior of the nanofluid. By applying the linear stability theory and a normal mode analysis method, the dispersion relation has been derived. For the case of stationary convection, it is observed that the Walters’ (model B’) elastico-viscous nanofluid behaves like an ordinary Newtonian nanofluid. The effects of the various physical parameters of the system, namely, the concentration Rayleigh number, Prandtl number, capacity ratio, Lewis number and kinematics visco-elasticity coefficient on the stability of the system has been numerically investigated. In addition, sufficient conditions for the non-existence of oscillatory convection are also derived.

Źródło:

Bulletin of the Polish Academy of Sciences. Technical Sciences; 2015, 63, 1; 235-244
0239-7528

Pojawia się w:

Bulletin of the Polish Academy of Sciences. Technical Sciences

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 5.

Tytuł:

Sensitivities of the Tiedtke and Kain-Fritsch Convection Schemes for RegCM4.5 over West Africa

Autorzy:

Adeniyi, Mojisola Oluwayemisi

Powiązania:

https://bibliotekanauki.pl/articles/108457.pdf

Data publikacji:

2019

Wydawca:

Instytut Meteorologii i Gospodarki Wodnej - Państwowy Instytut Badawczy

Tematy:

convective precipitation
West African monsoon
Kain-Fritsch convection scheme
Tiedtke convection scheme
African easterly jet

Opis:

Realistic simulation of weather and climate parameters over West Africa is daunting, so the performance of the Tiedtke and Kain-Fritsch convection schemes within version 4.5 of the Regional Climate Model (RegCM4.5) of the International Centre for Theoretical Physics, Trieste is evaluated over West Africa for improved simulation. The two schemes are compared to two traditional mixture schemes (Grell on land and Emanuel on Ocean), outperforming the mixture schemes with reduced magnitude and spatial coverage of dry bias. Both schemes simulate precipitation over West Africa with a low dry bias, however, the Kain-Fritsch convection scheme simulates more realistic precipitation in the West African convective environment. This is associated with the inclusion of a variable cloud radius and the convective available potential energy closure for the Kain-Fritsch in contrast to a fixed cloud radius and moisture convergence of the of the Tiedtke scheme. The simulated outgoing longwave radiation and omega lend support to the spatial variations and amount of simulated precipitation in the different areas by the schemes. The spatial variation of simulated temperature over the target region shows lower bias than precipitation by all the convection schemes. Soil moisture is more accurately simulated (correlation coefficient ~1) in the savannah (8-10°N) and Sahel (22-28°N) environments by all the convection schemes. Tiedtke performs the most accurate simulations of the pattern and profile of zonal wind which controls climate circulation, with slightly weaker simulations of the Africa easterly jet with core magnitude less than 10 m·s-1. The accuracy of the KF and Tiedtke in RegCM4.5 in simulating the climate of West Africa is documented for the first time for application in future studies over the region.

Źródło:

Meteorology Hydrology and Water Management. Research and Operational Applications; 2019, 7, 2; 27-37
2299-3835
2353-5652

Pojawia się w:

Meteorology Hydrology and Water Management. Research and Operational Applications

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 6.

Tytuł:

Global stability for thermal convection in a couple-stress fluid with temperature and pressure dependent viscosity

Autorzy:

Choudhary, S. S.
Bharti, P. K.

Powiązania:

https://bibliotekanauki.pl/articles/178230.pdf

Data publikacji:

2013

Wydawca:

Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej

Tematy:

konwekcja
konwekcja cieplna
stabilność
płyn nieniutonowski
convection
thermal convection
stability
non-Newtonian fluid

Opis:

We show that the global nonlinear stability threshold for convection in a couple-stress fluid with temperature and pressure dependent viscosity is exactly the same as the linear instability boundary. This optimal result is important because it shows that linearized instability theory has captured completely the physics of the onset of convection. It has also been found that the couplestress fluid is more stable than the ordinary viscous fluid and then the effect of couple-stress parameter (F) and variable dependent viscosity (Γ) on the onset of convection is also analyzed.

Źródło:

Studia Geotechnica et Mechanica; 2013, 35, 3; 85-102
0137-6365
2083-831X

Pojawia się w:

Studia Geotechnica et Mechanica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 7.

Tytuł:

A Numerical Study of Combined Natural and Marangoni Convection in a Square Cavity

Autorzy:

Cicek, K.
Baytas, A.

Powiązania:

https://bibliotekanauki.pl/articles/116928.pdf

Data publikacji:

2009

Wydawca:

Uniwersytet Morski w Gdyni. Wydział Nawigacyjny

Tematy:

Numerical Study
Square Cavity
natural convection
Marangoni Convection
Buoyancy-Driven Flow
Thermo Capillary Flow
Navier-Stokes Equations
Rayleigh Number

Opis:

Through the aim of this study, the effects of combined buoyancy-driven flows and thermo capillary flows, which are emerged from temperature differences, on fluid flow and heat transfer numerically investigated with differentially heated side walls in a free surface square cavity. The study has been accomplished with three milestones to achieve the right solutions. For every milestone Navier-Stokes, continuity and energy equations are discretized by using finite volume method and grids with 52 x 52 control volumes. Results are presented Pr=1, Pr=7 and Pr=100. The effect of positive and negative Marangoni number on fluid flow and heat transfer at different Rayleigh number are considered and discussed.

Źródło:

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2009, 3, 2; 173-178
2083-6473
2083-6481

Pojawia się w:

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 8.

Tytuł:

Triple- diffusive convection in a micropolar ferrofluid in the presence of rotation

Autorzy:

Chand, S.

Powiązania:

https://bibliotekanauki.pl/articles/265647.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja
konwekcja cieplna
substancja rozpuszczalna
pole magnetyczne
namagnesowanie
triple- diffusive convection
micropolar ferrofluid
thermal convection
solute gradient
vertical magnetic field
rotation
magnetization

Opis:

This paper deals with the theoretical investigation of the triple-diffusive convection in a micropolar ferrofluid layer heated and soluted below subjected to a transverse uniform magnetic field in the presence of uniform vertical rotation. For a flat fluid layer contained between two free boundaries, an exact solution is obtained. A linear stability analysis theory and normal mode analysis method have been employed to study the onset convection. The influence of various parameters like rotation, solute gradients, and micropolar parameters (i.e., the coupling parameter, spin diffusion parameter and micropolar heat conduction parameter) on the onset of stationary convection has been analyzed. The critical magnetic thermal Rayleigh number for the onset of instability is also determined numerically for sufficiently large value of the buoyancy magnetization parameter M1 (ratio of the magnetic to gravitational forces). The principle of exchange of stabilities is found to hold true for the micropolar fluid heated from below in the absence of micropolar viscous effect, microinertia, solute gradient and rotation. The oscillatory modes are introduced due to the presence of the micropolar viscous effect, microinertia , solute gradient and rotation, which were non-existent in their absence. In this paper, an attempt is also made to obtain the sufficient conditions for the non-existence of overstability.

Źródło:

International Journal of Applied Mechanics and Engineering; 2013, 18, 2; 307-327
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 9.

Tytuł:

A Neumann problem for a convection-diffusion equation on the half-line

Autorzy:

Biler, Piotr
Karch, Grzegorz

Powiązania:

https://bibliotekanauki.pl/articles/1207965.pdf

Data publikacji:

2000

Wydawca:

Polska Akademia Nauk. Instytut Matematyczny PAN

Tematy:

Neumann problem
asymptotics of solutions.
convection-diffusion equation

Opis:

We study solutions to a nonlinear parabolic convection-diffusion equation on the half-line with the Neumann condition at x=0. The analysis is based on the properties of self-similar solutions to that problem.

Źródło:

Annales Polonici Mathematici; 2000, 74, 1; 79-95
0066-2216

Pojawia się w:

Annales Polonici Mathematici

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 10.

Tytuł:

Natural convection in a partially heated cylinder: A numerical study

Autorzy:

Núñez, José
Beltrán, Alberto
Rivero, Michel

Powiązania:

https://bibliotekanauki.pl/articles/2055060.pdf

Data publikacji:

2021

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

bifurcations
natural convection
partially heated cylinder
switching modes solutions

Opis:

This work presents a numerical study on a natural convective flow in a cylindrical container heated from below, cooled from above, and partially heated from the lateral wall. Mass, momentum and energy equations were solved with a developed hybrid Fourier-finite volume code and validated with the commercial software COMSOL Multiphysics for steady-state solutions. The primary solutions correspond to steady-states Cm with azimuthal wavenumbers m. The results show mode competition between different states leading to many flow solutions including steady axisymmetric, steady non-axisymmetric, time-dependent pulsating wave solutions, and other flow states with a variety of spatiotemporal symmetries.

Źródło:

Journal of Theoretical and Applied Mechanics; 2021, 59, 4; 623--636
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 11.

Tytuł:

Mixed convection heat transfer in trapezoidal lid-driven cavity with uniformly heated inner circular cylinder

Autorzy:

Hussein, Asmaa Ali

Powiązania:

https://bibliotekanauki.pl/articles/27312211.pdf

Data publikacji:

2023

Wydawca:

Polska Akademia Nauk. Czasopisma i Monografie PAN

Tematy:

cavity
heat transfer
mixed convection
lid-driven

Opis:

The present work comprises a numerical analysis using the Ansys program to solve the problem of combined free-forced convection around a circular cylinder located in a horizontal lid-driven trapezoidal enclosure. The enclosure is filled with water. The upper moving wall and lower fixed wall are cold at a constant temperature, whereas the inclined walls are adiabatically insulated. The uniformly heated cylinder is located at different positions in the cavity. The study covers three values of Richardson number (0.01, 1, and 10). The results show that the streamlines and isotherms in the enclosure, the Nusselt number and friction factor in the moving wall, hot wall and bottom wall are strongly dependent on the position of the inner hot cylinder. The results are validated with previous work, and the comparison gives good agreement.

Źródło:

Archives of Thermodynamics; 2023, 44, 3; 99--118
1231-0956
2083-6023

Pojawia się w:

Archives of Thermodynamics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 12.

Tytuł:

Natural convection from four circular cylinders in across arrangement within horizontal annular space

Autorzy:

Laidoudi, Houssem

Powiązania:

https://bibliotekanauki.pl/articles/387589.pdf

Data publikacji:

2020

Wydawca:

Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej

Tematy:

natural convection
multiple cylinders
annular space
heat transfer
numerical simulation

Opis:

Numerical investigation is accomplished to study the roles of governing parameters of natural convection on the fluid motion and heat transfer rate of four heated circular cylinders placed inside a circular enclosure of cold surface. The cylinders are positioned in across arrangement. The representative results are obtained within the ranges of initial conditions as: Prandtl number (Pr = 7.1 to 1000) and Rayleigh number (Ra = 103 to 105). The average Nusselt number of each inner cylinder is computed. The effects of thermal buoyancy strength on the fluid motion and temperature are also illustrated. It was found that the heat transfer rate of cylinders depends significantly on the position inside the enclosure. Moreover, the role of Prandtl number on flow and thermal patterns is negligible. The values of Nusselt number are also given, which can be useful for some engineering applications.

Źródło:

Acta Mechanica et Automatica; 2020, 14, 2; 98-102
1898-4088
2300-5319

Pojawia się w:

Acta Mechanica et Automatica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 13.

Tytuł:

A functional-analytic approach to turbulent convection

Autorzy:

Szafirski, B.

Powiązania:

https://bibliotekanauki.pl/articles/715419.pdf

Data publikacji:

1970

Wydawca:

Polska Akademia Nauk. Instytut Matematyczny PAN

Źródło:

Annales Polonici Mathematici; 1970, 23, 1; 7-24
0066-2216

Pojawia się w:

Annales Polonici Mathematici

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 14.

Tytuł:

The modified XFEM for solving problems of a phase change with natural convection

Autorzy:

Stąpór, Paweł

Powiązania:

https://bibliotekanauki.pl/articles/139838.pdf

Data publikacji:

2019

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

phase change
natural convection
extended finite element method
level set method

Opis:

This paper presents an extended finite element method applied to solve phase change problems taking into account natural convection in the liquid phase. It is assumed that the transition from one state to another, e.g., during the solidification of pure metals, is discontinuous and that the physical properties of the phases vary across the interface. According to the classical Stefan condition, the location, topology and rate of the interface changes are determined by the jump in the heat flux. The incompressible Navier–Stokes equations with the Boussinesq approximation of the natural convection flow are solved for the liquid phase. The no-slip condition for velocity and the melting/freezing condition for temperature are imposed on the interface using penalty method. The fractional four-step method is employed for analysing conjugate heat transfer and unsteady viscous flow. The phase interface is tracked by the level set method defined on the same finite element mesh. A new combination of extended basis functions is proposed to approximate the discontinuity in the derivative of the temperature, velocity and the pressure fields. The single-mesh approach is demonstrated using three two-dimensional benchmark problems. The results are compared with the numerical and experimental data obtained by other authors.

Źródło:

Archive of Mechanical Engineering; 2019, LXVI, 3; 273-294
0004-0738

Pojawia się w:

Archive of Mechanical Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 15.

Tytuł:

Effect of vertical vibrations on the onset of binary convection

Autorzy:

Swamy, M. S.

Powiązania:

https://bibliotekanauki.pl/articles/265645.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

grawitacja
metoda perturbacji
funkcja Rayleigha
gravity modulation
g-jitter
double diffusive convection
perturbation method

Opis:

In the present work the linear stability analysis of double diffusive convection in a binary fluid layer is performed. The major intention of this study is to investigate the influence of time-periodic vertical vibrations on the onset threshold. A regular perturbation method is used to compute the critical Rayleigh number and wave number. A closed form expression for the shift in the critical Rayleigh number is calculated as a function of frequency of modulation, the solute Rayleigh number, Lewis number, and Prandtl number. These parameters are found to have a significant influence on the onset criterion; therefore the effective control of convection is achieved by proper tuning of these parameters. Vertical vibrations are found to enhance the stability of a binary fluid layer heated and salted from below. The results of this study are useful in the areas of crystal growth in micro-gravity conditions and also in material processing industries where vertical vibrations are involved.

Źródło:

International Journal of Applied Mechanics and Engineering; 2013, 18, 3; 899-910
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 16.

Tytuł:

A Mechanistic Model of a Passive Autocatalytic Hydrogen Recombiner

Autorzy:

Rożeń, A.

Powiązania:

https://bibliotekanauki.pl/articles/184900.pdf

Data publikacji:

2015

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

hydrogen
catalysis
laminar flow
natural convection
forced convection
wodór
kataliza
przepływ laminarny
konwekcja naturalna
konwekcja wymuszona

Opis:

A passive autocatalytic hydrogen recombiner (PAR) is a self-starting device, without operator action or external power input, installed in nuclear power plants to remove hydrogen from the containment building of a nuclear reactor. A new mechanistic model of PAR has been presented and validated by experimental data and results of Computational Fluid Dynamics (CFD) simulations. The model allows to quickly and accurately predict gas temperature and composition, catalyst temperature and hydrogen recombination rate. It is assumed in the model that an exothermic recombination reaction of hydrogen and oxygen proceeds at the catalyst surface only, while processes of heat and mass transport occur by assisted natural and forced convection in non-isothermal and laminar gas flow conditions in vertical channels between catalyst plates. The model accounts for heat radiation from a hot catalyst surface and has no adjustable parameters. It can be combined with an equation of chimney draft and become a useful engineering tool for selection and optimisation of catalytic recombiner geometry.

Źródło:

Chemical and Process Engineering; 2015, 36, 1; 3-19
0208-6425
2300-1925

Pojawia się w:

Chemical and Process Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 17.

Tytuł:

The onset of thermal convection in couple-stress fluid in hydromagnetics saturating a porous medium

Autorzy:

Rana, G. C.

Powiązania:

https://bibliotekanauki.pl/articles/201216.pdf

Data publikacji:

2014

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

couple stress fluid
magnetic field
porous medium
thermal convection

Opis:

In this paper, the effect of magnetic field on thermal convection in couple-stress fluid saturating a porous medium is considered. By applying linear stability theory and the normal mode analysis method, a mathematical theorem is derived which states that the viscoelastic thermal convection at marginal state, cannot manifest as stationary convection if the thermal Rayleigh number R, the medium permeability parameter Pι the couple-stress parameter F and the Chandrasekher number Q, satisfy the inequality R ≤4π²/P_l (1 + 2π²F + P_lQ/2ε) the result clearly establishes the stabilizing character of couple-stress parameter and magnetic field whereas destabilizing character of medium permeability.

Źródło:

Bulletin of the Polish Academy of Sciences. Technical Sciences; 2014, 62, 2; 357-362
0239-7528

Pojawia się w:

Bulletin of the Polish Academy of Sciences. Technical Sciences

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 18.

Tytuł:

On the numerical solutions of convection-diffusion equations

Autorzy:

Axelsson, O.

Powiązania:

https://bibliotekanauki.pl/articles/720813.pdf

Data publikacji:

1984

Wydawca:

Polska Akademia Nauk. Instytut Matematyczny PAN

Źródło:

Banach Center Publications; 1984, 13, 1; 165-184
0137-6934

Pojawia się w:

Banach Center Publications

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 19.

Tytuł:

Nonstationary Marangoni convection

Autorzy:

Wagner, Alfred

Powiązania:

https://bibliotekanauki.pl/articles/1338845.pdf

Data publikacji:

1999

Wydawca:

Polska Akademia Nauk. Instytut Matematyczny PAN

Tematy:

free boundary
nonstationary
Navier-Stokes

Źródło:

Applicationes Mathematicae; 1999, 26, 2; 195-220
1233-7234

Pojawia się w:

Applicationes Mathematicae

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 20.

Tytuł:

Open-Source CFD analysis of multi-domain unsteady heating with natural convection

Autorzy:

Sosnowski, P.
Pozorski, J.

Powiązania:

https://bibliotekanauki.pl/articles/1943189.pdf

Data publikacji:

2009

Wydawca:

Politechnika Gdańska

Tematy:

CFD
open source software
unsteady heating
natural convection
multi-domain heat transfer

Opis:

The paper presents the capabilities of open-source programs used for numerical simulation of fluid flow and heat transfer phenomena. These tools are applied for unsteady problems with natural convection and, in particular, the heating of an automotive headlight. To perform these studies, a solver was created using an open-source C++ library OpenFOAM. The implementation problems encountered were, inter alia, dealing with multi-domain computation and coupling of sub-domains. The presented simulation results clearly show that open-source software can readily be applied also to engineering problems and can compete with commercial packages.

Źródło:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2009, 13, 4; 403-414
1428-6394

Pojawia się w:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 21.

Tytuł:

Upper Bounds for the Complex Growth Rate of a Disturbance in Ferrothermohaline Convection

Autorzy:

Ram, Kaka
Prakash, Jyoti
Kumari, Kultaran
Kumar, Pankaj

Powiązania:

https://bibliotekanauki.pl/articles/2086773.pdf

Data publikacji:

2022

Wydawca:

Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej

Tematy:

linear stability
ferrofluid
oscillatory motions
ferrothermohaline convection

Opis:

It is proved analytically that the complex growth rate σ= σr+iσi (σr and σi are the real and imaginary parts of σ, respectively) of an arbitrary oscillatory motion of neutral or growing amplitude in ferrothermohaline convection in a ferrofluid layer for the case of free boundaries is located inside a semicircle in the right half of the σrσi-plane, whose center is at the origin (formula) where Rs is the concentration Rayleigh number, Pr′ is the solutal Prandtl number, M1′ is the ratio of magnetic flux due to concentration fluctuation to the gravitational force, and M5 is the ratio of concentration effect on magnetic field to pyromagnetic coefficient. Further, bounds for the case of rigid boundaries are also derived separately.

Źródło:

Studia Geotechnica et Mechanica; 2022, 44, 2; 114--122
0137-6365
2083-831X

Pojawia się w:

Studia Geotechnica et Mechanica

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 22.

Tytuł:

The combined heat transfer of radiation and mixed convection analysis in a lid-driven trapezoidal cavity

Autorzy:

Mohammadi, M.
Gandjalikhan Nassab, S. A.

Powiązania:

https://bibliotekanauki.pl/articles/279609.pdf

Data publikacji:

2015

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

mixed convection
radiation
lid-driven trapezoidal cavity

Opis:

In this paper, the effect of radiation heat transfer on mixed convection in a lid-driven trapezoidal cavity is studied numerically. The governing equations of mixed convection are solved based on the SIMPLE algorithm and the solution of the radiative transfer equation inside the participating medium is carried out using the discrete ordinates method, simultaneously. To study the heat transfer and flow characteristics, sensitivity analysis is carried out based on the two parameters including the optical thickness and radiation-conduction parameter. Several interesting results are obtained such as sweep behavior on the isotherms, streamlines and convective Nusselt number with optical thicknesses.

Źródło:

Journal of Theoretical and Applied Mechanics; 2015, 53, 3; 643-652
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 23.

Tytuł:

Upwind FEM for convection dominated elliptic problems

Autorzy:

Risch, U.
Lube, G.

Powiązania:

https://bibliotekanauki.pl/articles/720645.pdf

Data publikacji:

1990

Wydawca:

Polska Akademia Nauk. Instytut Matematyczny PAN

Źródło:

Banach Center Publications; 1990, 24, 1; 501-508
0137-6934

Pojawia się w:

Banach Center Publications

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 24.

Tytuł:

Penetrative convection due to absorption of radiation in a magnetic nanofluid saturated porous layer

Autorzy:

Mahajan, Amit
Sharma, Mahesh Kumar

Powiązania:

https://bibliotekanauki.pl/articles/178577.pdf

Data publikacji:

2019

Wydawca:

Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej

Tematy:

magnetic nanofluids
penetrative convection
Darcy model
radiation absorption
magnetic field

Opis:

The present study investigates the onset of penetrative convection induced by selective absorption of radiation in a magnetic nanofluid saturated porous medium. The influence of Brownian motion, thermophoresis, and magnetophoresis on magnetic nanofluid treatment is taken into consideration. The Darcy’s model is selected for the porous medium. We conduct a linear stability analysis to examine the onset of instability and evaluate the results for two different configurations, namely, when the layer is heated from below and when the layer is heated from above. The numerical investigations are carried out by applying the Chebyshev pseudospectral method. The effect of the porosity parameter E, parameter Y (represents the ratio of internal heating to boundary heating), Lewis number Le, concentration Rayleigh number Rn, Langevin parameter αL, width of nanofluid layer d, diffusivity ratio η, and modified diffusivity ratio NA is examined at the onset of convection. The results indicate that the convection commences easily with an increase in the value of Y, Le, and NA but opposite in the case with a decrease in the value of E, αL, η and d for both the two configurations. The parameter Rn advances the onset of convection when the layer is heated from below, while delays the onset of convection when the layer is heated from above.

Źródło:

Studia Geotechnica et Mechanica; 2019, 41, 3; 129-142
0137-6365
2083-831X

Pojawia się w:

Studia Geotechnica et Mechanica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 25.

Tytuł:

Electro-hydrodynamic convection in a rotating dielectric micropolar fluid layer

Autorzy:

Kaur, H.
Verma, G. N.

Powiązania:

https://bibliotekanauki.pl/articles/264654.pdf

Data publikacji:

2019

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja
liczba Rayleigha
liczba Taylora
convection
rotation
electric
Rayleigh number
Taylor number
normal mode

Opis:

Thermal convection of a rotating dielectric micropolar fluid layer under the action of an electric field and temperature gradient has been investigated. The dispersion relation has been derived using normal mode analysis. The effects of the electric Rayleigh number, micropolar viscosity, Taylor number and Prandtl number on stability and over stability criteria are discussed. It is found that rotation postpones the instability in the fluid layer, while the Prandtl number and rotation both have a stabilizing effect. It is also observed that the micropolar fluid additives have a stabilizing effect, whereas the electric field has a destabilizing effect on the onset of convection stability.

Źródło:

International Journal of Applied Mechanics and Engineering; 2019, 24, 4; 106-124
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 26.

Tytuł:

Experimental and numerical investigations of natural convection phenomena in a fermentation tank

Autorzy:

Klembt, Daniel
Meironke, Heiko

Powiązania:

https://bibliotekanauki.pl/articles/95195.pdf

Data publikacji:

2019

Wydawca:

Politechnika Koszalińska. Wydawnictwo Uczelniane

Tematy:

ultrasonic doppler velocimetry
numerical simulation
natural convection flow
welocymetria dopplerowska
symulacja numeryczna
przepływ konwekcyjny

Opis:

In the context of investigations of real multiphase flows, the university has its own 350 litre fermentation tank with comprehensive acoustic flow and temperature measurement technology for the systematically investigation, of the influence of the fermentation activity, distribution of yeast and occurring convection phenomena. Due to the many problems with the optical (e.g. PIV) and acoustic (e.g. UDV) measurement in a real fermenting fluid the numerical simulation was already used in earlier publications. To validate the numerical models, extensive experimental investigations were carried out which show that the flow in the fermenter is caused only by the reaction products of the yeast and the cooling panels and controls the yeast distribution. In this paper, both the numerical (CFD) and the experimental investigations serve as a starting point to influence the yeast distribution. The described convection flow can only temporarily guarantee the uniform distribution of the yeast in the fermenter until the sedimentation of the yeast at the tank bottom (bottom-fermenting yeast) finally begins. The aim of the investigation is to influence the convection flow in certain zones by targeted cooling or heating of the jackets in such a way that a uniform spatial distribution of the yeast over the entire fermentation process is ensured and thus optimal conditions for its metabolic processes are given. Finally, the numerical simulation is validated with the experimental data.

Źródło:

Journal of Mechanical and Energy Engineering; 2019, 3, 3; 235-244
2544-0780
2544-1671

Pojawia się w:

Journal of Mechanical and Energy Engineering

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 27.

Tytuł:

Exact difference schemes and schemes of higher order of approximation for convection-diffusion equation. I

Autorzy:

Lapinska-Chrzczonowicz, M.
Matus, P.

Powiązania:

https://bibliotekanauki.pl/articles/106186.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Marii Curie-Skłodowskiej. Wydawnictwo Uniwersytetu Marii Curie-Skłodowskiej

Tematy:

convection-diffusion equation
initial-boundary value problem
traveling wave
EDS

Opis:

The initial-boundary value problem for a convection-diffusion equation [formula] is considered. The difference scheme, approximating this problem, is constructed. It is shown that for traveling wave solutions the scheme is exact (EDS). The monotonicity of the scheme is also taken into consideration. Presented numerical experiments illustrate the theoretical results investigated in the paper.

Źródło:

Annales Universitatis Mariae Curie-Skłodowska. Sectio AI, Informatica; 2013, 13, 1; 37-51
1732-1360
2083-3628

Pojawia się w:

Annales Universitatis Mariae Curie-Skłodowska. Sectio AI, Informatica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 28.

Tytuł:

Chaotic convection of viscoelastic fluid in porous medium under G-jitter

Autorzy:

Bhadauria, B. S.
Singh, A.
Singh, M. K.

Powiązania:

https://bibliotekanauki.pl/articles/265559.pdf

Data publikacji:

2019

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

teoria nieliniowa
grawitacja
konwekcja
non-linear theory
gravity modulation
chaotic convection

Opis:

The present article aims at investigating the effect of gravity modulation on chaotic convection of a viscoelastic fluid in porous media. For this, the problem is reduced into Lorenz system (non-autonomous) by employing the truncated Galerkin expansion method. The system shows transitions from periodic to chaotic behavior on increasing the scaled Rayleigh number R. The amplitude of modulation advances the chaotic nature in the system while the frequency of modulation has a tendency to delay the chaotic behavior which is in good agreement with the results due to [1]. The behavior of the scaled relaxation and retardation parameter on the system is also studied. The phase portrait and time domain diagrams of the Lorenz system for suitable parameter values have been used to analyze the system.

Źródło:

International Journal of Applied Mechanics and Engineering; 2019, 24, 1; 37-51
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 29.

Tytuł:

Compressible analysis of Bénard convection of magneto rotatory couple-stress fluid

Autorzy:

Mehta, C. B.
Singh, M.

Powiązania:

https://bibliotekanauki.pl/articles/264669.pdf

Data publikacji:

2018

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja termiczna
pole magnetyczne
rotacja
ściśliwość
couple-stress fluid
compressibility
rotation
magnetic field
thermal convection

Opis:

Thermal Instability (Benard’s Convection) in the presence of uniform rotation and uniform magnetic field (separately) is studied. Using the linearized stability theory and normal mode analyses the dispersion relation is obtained in each case. In the case of rotatory Benard’s stationary convection compressibility and rotation postpone the onset of convection whereas the couple-stress have duel character onset of convection depending on rotation parameter. While in the absence of rotation couple-stress always postpones the onset of convection. On the other hand, magnetic field on thermal instability problem on couple-stress fluid for stationary convection couple-stress parameter and magnetic field postpones the onset of convection. The effect of compressibility also postpones the onset of convection in both cases as rotation and magnetic field. Graphs have been plotted by giving numerical values to the parameters to depict the stationary characteristics. Further, the magnetic field and rotation are found to introduce oscillatory modes which were non-existent in their absence and then the principle of exchange of stability is valid. The sufficient conditions for non-existence of overstability are also obtained.

Źródło:

International Journal of Applied Mechanics and Engineering; 2018, 23, 1; 91-105
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 30.

Tytuł:

Marangoni convection in a relatively hotter or cooler liquid layer with free boundaries

Autorzy:

Gupta, A. K.
Shandil, R. G.

Powiązania:

https://bibliotekanauki.pl/articles/265233.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

napięcie powierzchniowe
konwekcja
przewodzenie
stabilność liniowa
surface tension
convection
conducting
linear stability

Opis:

In this paper, we study the onset of cellular convection in a horizontal fluid layer heated from below, with a free-slip boundary condition at the bottom when the driving mechanism is surface tension at the upper free surface, in the light of the modified analysis of Banerjee et al. (Jour. Math. & Phys. Sci., 1983, 17, 603). This leads to a formulation of the problem which depends upon whether the liquid layer is relatively hotter or cooler. It is found that the phenomenon of surface tension driven instability problems should not only depend upon the Marangoni number which is proportional to the maintained temperature differences across the layer but also upon another parameter that arises due to variation in the specific heat at constant volume on account of the variations in temperature. Numerical results are obtained for the problem wherein the lower free boundary is perfectly thermally conducting.

Źródło:

International Journal of Applied Mechanics and Engineering; 2013, 18, 2; 581-588
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 31.

Tytuł:

Inclination angle implications for fluid flow and mixed convection in complex geometry enclosure-meshless numerical analyses

Autorzy:

Najafi, M.
Nikfar, M.
Arefmanesh, A.

Powiązania:

https://bibliotekanauki.pl/articles/279898.pdf

Data publikacji:

2015

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

meshless
Petrov-Galerkin
mixed convection
rectangular cavity
wavy wall

Opis:

The meshless local Petrov-Galerkin (MLPG) method is extended to analyze the mixed convection and fluid flow in an inclined two-dimensional lid-driven cavity. The enclosure considered comprises two insulated vertical walls and a wavy bottom wall which is subjected to a higher constant temperature than its top counterpart, the sliding lid. For the proposed scheme, the stream function formulation with a weighting function of unity is employed. The simulation results reveal that the local Nusselt number increases with a clockwise increase in the inclination angle. Also, a decrease in the aspect ratio results in an increase in the hot wavy wall average Nusselt number.

Źródło:

Journal of Theoretical and Applied Mechanics; 2015, 53, 3; 519-530
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 32.

Tytuł:

Zużycie moralne pieców konwekcyjno-parowych
Normal wear of convection-cum-vapour furnaces

Autorzy:

Diakun, J.
Zawisza, K.

Powiązania:

https://bibliotekanauki.pl/articles/290653.pdf

Data publikacji:

2006

Wydawca:

Polskie Towarzystwo Inżynierii Rolniczej

Tematy:

piec konwekcyjno-parowy
ocena techniczna
zużycie moralne
convection and vapour furnace
technical assessment
normal wear

Opis:

Artykuł jest próbą opracowania metody oceny zużycia moralnego urządzeń na przykładzie pieców konwekcyjno-parowych. Poddano analizie trzy piece konwekcyjno-parowe z różnych okresów produkcji. Ocenę zużycia moralnego przeprowadzono na podstawie analizy porównawczej postępu technicznego jaki dokonał się w konstrukcji pieców konwekcyjno-parowych.
The article is an attempt to develop a method of assessment of normal wear of appliances on the basis of the example of convection-cum-vapour furnaces. Three convection-cum-vapour furnaces from different time of production were analysed. Wear assessment was done on the basis of a comparative analysis of technological progress that took place in the structure of convection and stream furnaces.

Źródło:

Inżynieria Rolnicza; 2006, R. 10, nr 7(82), 7(82); 83-89
1429-7264

Pojawia się w:

Inżynieria Rolnicza

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 33.

Tytuł:

Intensification of free-convection heat transfer in magnetically assisted bioreactor

Autorzy:

Konopacki, Maciej
Kordas, Marian
Rakoczy, Rafał

Powiązania:

https://bibliotekanauki.pl/articles/185473.pdf

Data publikacji:

2019

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

natural convection
rotating magnetic field
magnetically assisted bioreactor
Naturalna konwekcja
wirujące pole magnetyczne
bioreaktor wspomagany magnetycznie

Opis:

The effect of rotating magnetic field on the heat transfer process in a magnetically assisted bioreactor was studied experimentally. Experimental investigations are provided for the explanation of the influence of the rotating magnetic field on natural convection. The heat transfer coefficients and the Nusselt numbers were determined as a function of the product of Grashof and Prandtl dimensionless numbers. Moreover, the comparison of the thermal performance between the tested set-up and a vertical cylinder was carried out. The relative enhancement of heat transfer was characterized by the rate of the relative heat transfer intensification. The study showed that along with the intensity of the magnetic field the heat transfer increased.

Źródło:

Chemical and Process Engineering; 2019, 40, 3; 293--304
0208-6425
2300-1925

Pojawia się w:

Chemical and Process Engineering

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 34.

Tytuł:

Inverse Solution to the Vertical Plate Cooling by Radiation and Convection in Air

Autorzy:

Hadała, Beata
Malinowski, Zbigniew
Gołdasz, Andrzej
Cebo-Rudnicka, Agnieszka

Powiązania:

https://bibliotekanauki.pl/articles/2134090.pdf

Data publikacji:

2022

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

convection heat transfer
radiation heat transfer
plate emissivity
vertical plate

Opis:

The inverse solution to the heat flux identification during the vertical plate cooling in air has been presented. The developed solution allowed to separate the energy absorbed by the chamber due to radiation from the convection heat losses to air. The uncertainty tests were carried out and the accuracy of the solution has been estimated at a level of 1%-5% depending on the boundary condition model. The inverse solution was obtained for the temperature measurements in the vertical plate. The stainless-steel plate was heated to 950°C and then cooled in the chamber in air only to about 30°C. The identified heat transfer coefficient was compared with the Churchill and Chu model. The solution has allowed to separate the radiation heat losses and to determine the Nusselt number values that stay in good agreement with the Churchill and Chu model for a nearly steady-state air flow for the plate temperature below 100°C.

Źródło:

Archives of Metallurgy and Materials; 2022, 67, 3; 1167--1178
1733-3490

Pojawia się w:

Archives of Metallurgy and Materials

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 35.

Tytuł:

A dynamically adaptive lattice Boltzmann method for thermal convection problems

Autorzy:

Feldhusen, K.
Deiterding, R.
Wagner, C.

Powiązania:

https://bibliotekanauki.pl/articles/331394.pdf

Data publikacji:

2016

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

lattice Boltzmann method
adaptive mesh refinement
thermal convection
incompressible
metoda siatkowa Boltzmanna
adaptacyjne zagęszczanie siatki
konwekcja termiczna

Opis:

Utilizing the Boussinesq approximation, a double-population incompressible thermal lattice Boltzmann method (LBM) for forced and natural convection in two and three space dimensions is developed and validated. A block-structured dynamic adaptive mesh refinement (AMR) procedure tailored for the LBM is applied to enable computationally efficient simulations of moderate to high Rayleigh number flows which are characterized by a large scale disparity in boundary layers and free stream flow. As test cases, the analytically accessible problem of a two-dimensional (2D) forced convection flow through two porous plates and the non-Cartesian configuration of a heated rotating cylinder are considered. The objective of the latter is to advance the boundary conditions for an accurate treatment of curved boundaries and to demonstrate the effect on the solution. The effectiveness of the overall approach is demonstrated for the natural convection benchmark of a 2D cavity with differentially heated walls at Rayleigh numbers from 10³ up to 10⁸. To demonstrate the benefit of the employed AMR procedure for three-dimensional (3D) problems, results from the natural convection in a cubic cavity at Rayleigh numbers from 10³ up to 10⁵ are compared with benchmark results.

Źródło:

International Journal of Applied Mathematics and Computer Science; 2016, 26, 4; 735-747
1641-876X
2083-8492

Pojawia się w:

International Journal of Applied Mathematics and Computer Science

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 36.

Tytuł:

Analysis of components effecting free convection intensity in steel rectangular sections

Autorzy:

Wyczółkowski, R.

Powiązania:

https://bibliotekanauki.pl/articles/240388.pdf

Data publikacji:

2015

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

free convection
Rayleigh number
section bundles
effective thermal conductivity
heat treatment
konwekcja swobodna
liczbia Rayleigha
efektywna przewodność cieplna
obróbka cieplna

Opis:

Free convection is one of the heat transfer modes which occurs within the heat-treated bundles of steel rectangular section. A comprehensive study of this phenomenon is necessary for optimizing the heating process of this type of charge. The free convection intensity is represented by the Rayleigh number Ra. The value of this criterion depends on the following parameters: the mean section temperature, temperature difference within the section, kinematic coefficient of viscosity, volume expansion coefficient and the Prandtl number. The paper presents the analysis of the impact of these factors on free convection in steel rectangular sections. The starting point for this analysis were the results of experimental examinations. It was found that the highest intensity of this process occurs for the temperature of 100°C. This is mainly caused by changes in the temperature difference observed in the area of sections and changes in kinematic coefficient of viscosity of air. The increase in the value of the Rayleigh number criterion at the initial stage is attributable to changes in the parameter of temperature difference within the section. After exceeding 100°C, the main effect on convection is from changes in air viscosity. Thus, with further increase in temperature, the Rayleigh number starts to decline rapidly despite further rise in the difference in temperature.

Źródło:

Archives of Thermodynamics; 2015, 36, 3; 105-121
1231-0956
2083-6023

Pojawia się w:

Archives of Thermodynamics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 37.

Tytuł:

Analiza zmian struktury wewnętrznej podczas konwekcyjnego suszenia pietruszki
Analysis of internal structure changes during parsley convection drying

Autorzy:

Łapczyńska-Kordon, B.

Powiązania:

https://bibliotekanauki.pl/articles/289738.pdf

Data publikacji:

2005

Wydawca:

Polskie Towarzystwo Inżynierii Rolniczej

Tematy:

suszenie konwekcyjne
komórka
powierzchnia
wymiar liniowy
pietruszka
convection drying
cell
area
linear dimension
parsley

Opis:

W pracy podjęto próbę przeanalizowania zmian struktury wewnętrznej pietruszki suszonej konwekcyjnie poprzez określenie zmian powierzchni poprzecznej oraz wymiarów charakterystycznych komórek tkankowych w zależności od zawartości wody w materiale, a takie opracowania modelu zmian tych wielkości od zawartości wody. Pietruszkę w postaci kostek suszono w suszarce z wymuszonym obiegiem powietrza w temperaturze 50°C. W czasie suszenia co 15 min. wyciągano próbki do analizy mikroskopowej, podczas której określano zmiany powierzchni i charakterystycznych wymiarów liniowych komórek. Na podstawie wyników stwierdzono, że w czasie suszenia zwiększa się ilość komórek o małej powierzchni przekroju poprzecznego. Ponadto zaobserwowano, że powierzchnia to oraz długość i szerokość komórek rosną w początkowym okresie suszenia, a w końcowym maleją. Zmiany powierzchni przekroju poprzecznego komórki i wymiarów liniowych od zawartości wody opisano modelami w postaci wielomianów trzeciego stopnia, których dokładność oceniono za pomocą współczynników determinacji, których wartości wyniosły w przypadku powierzchni R²= 0,76, wymiarów liniowych R²= 0,56.
The study shows an attempt to analyze internal structure changes in convection-dried parsley by determining changes in cross-section area and dimensions of characteristic tissue cells depending on water content in material, and also developments of model showing changes in these values from water content. Parsley in form of cubes was dried in a drier with forced air circulation at the temperature of 50°C. During drying, samples were taken every 15 min. for microscope analysis, during which changes in area and characteristic cell linear dimensions were being determined. Obtained results allowed to state that number of cells with small cross-section area increased while drying. Moreover, it was observed that this area, and cell length and width increase during initial drying period, and decrease in final drying stage. Changes in cell cross-section area and linear dimensions from water content were described through models in form of third degree polynomials, accuracy of which was assessed using determination coefficients (R² = 0.76 for area, and R²= 0.56 for linear dimensions).

Źródło:

Inżynieria Rolnicza; 2005, R. 9, nr 10, 10; 285-293
1429-7264

Pojawia się w:

Inżynieria Rolnicza

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 38.

Tytuł:

Influence of computational grid resolution on the quality of forecasts of dangerous convection phenomena: a case study of August 11, 2017

Autorzy:

Mazur, Andrzej
Duniec, Grzegorz

Powiązania:

https://bibliotekanauki.pl/articles/2166587.pdf

Data publikacji:

2022

Wydawca:

Instytut Meteorologii i Gospodarki Wodnej - Państwowy Instytut Badawczy

Tematy:

meteorological model
supercell
high-resolution approach
convection-permitting scale

Opis:

On August 11, 2017, a violent convection phenomenon took place in northwestern Poland, i.e., a storm combined with intense rainfall and hurricane winds. This paper presents an attempt to analyze this case by using the results of a numerical weather model, at grid spacings of 7 km, 2.8 km, and 0.7 km. Various convective indicators were analyzed to assess the nature of the event. The key question the authors try to answer is: „To what extent, if any, did a tenfold increase in resolution improve the quality of the numerical forecasts?” This question, however, has not been conclusively resolved. The most likely cause of this event was a supercell rapidly moving from south to northeast. This supercell's path has been mapped (qualitatively at least) by the Supercell Detection Index at all resolutions used. As the resolution increased, the forecasted maximum gusts also increased from 25 m/s in the domain with a resolution of 7 km to 35 m/s at a resolution of 2.8 km and up to about 50 m/s at the highest resolution of 0.7 km. A key conclusion is that the results of the model at a resolution of 2.8 km are much closer to reality than at 7 km. This effect did not pertain to differences between the 2.8 km and 0.7 km models. The latter increase in resolution did not significantly improve the quality of the forecast.

Źródło:

Meteorology Hydrology and Water Management. Research and Operational Applications; 2022, 10, 2; 1--18
2299-3835
2353-5652

Pojawia się w:

Meteorology Hydrology and Water Management. Research and Operational Applications

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 39.

Tytuł:

Behaviour of a non-newtonian fluid in a helical tube under the influence of thermal buoyancy

Autorzy:

Ramla, Mohamed
Laidoudi, Houssem
Bouzit, Mohamed

Powiązania:

https://bibliotekanauki.pl/articles/2105993.pdf

Data publikacji:

2022

Wydawca:

Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej

Tematy:

helical heat exchanger
mixed convection
forced convection
power-law fluids
Nusselt number

Opis:

This work is an evaluative study of heat transfer in the helical-type heat exchanger. The fluid used is non-Newtonian in nature and is defined by Oswald’s model. The work was performed numerically by solving each of the Navier–Stokes equations and the energy equation using the package ANSYS-CFX. Following are the aspects that have been dealt with in this paper: the effects of thermal buoyan-cy, fluid nature and the tube shape on the heat transfer, and the fluid comportment. The interpretation of the obtained results was done by analyzing the isotherms and the streamlines. The mean values of the Nusselt number were also obtained in terms of the studied parame-ters. The results of this research enabled us to arrive at the following conclusion: the intensity of thermal buoyancy and the nature of the fluid affect the heat transfer distribution but keep the overall rate of heat transfer the same.

Źródło:

Acta Mechanica et Automatica; 2022, 16, 2; 111--118
1898-4088
2300-5319

Pojawia się w:

Acta Mechanica et Automatica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 40.

Tytuł:

Exact solution of MHD mixed convection periodic flow in a rotating vertical channel with heat radiation

Autorzy:

Singh, K. D.

Powiązania:

https://bibliotekanauki.pl/articles/265295.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja mieszana
magnetohydrodynamika
promieniowanie cieplne
periodic flow
mixed convection
magnetohydrodynamic (MHD)
rotating system
heat radiation

Opis:

Magnetohydrodynamic (MHD) mixed convection flow of a viscous, incompressible and electrically conducting fluid in a vertical channel is analyzed analytically. A magnetic field of uniform strength is applied perpendicular to the planes of the channel walls. The fluid is acted upon by a periodic variation of the pressure gradient in the vertically upward direction. The temperature of one of the plates is non-uniform and the temperature difference of the walls of the channel is high enough to induce heat transfer due to radiation. The fluid and the channel rotate in unison with an angular velocity about the axis normal to the plates of the channel. An exact analytical solution of the problem is obtained. Two cases of small and large rotation have been considered to assess the effects of different parameters involved in the flow problem. The velocity field, the amplitude and the phase angle of the shear stress are shown graphically and discussed in detail. During analysis it is found that the flow problem studied by Makinde and Mhone (2005) is incorrect physically and mathematically.

Źródło:

International Journal of Applied Mechanics and Engineering; 2013, 18, 3; 853-869
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 41.

Tytuł:

Artificial neural network to predict the natural convection from vertical and inclined arrays of horizontal cylinders

Autorzy:

Amiri, A.
Karami, A.
Yousefi, T.
Zanjani, M.

Powiązania:

https://bibliotekanauki.pl/articles/779019.pdf

Data publikacji:

2012

Wydawca:

Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie

Tematy:

natural convection
Inclined Array
Vertical Array
modeling
artificial neural network

Opis:

The main focus of the present study is to utilize the artifi cial neural network (ANN) in predicting the natural convection from horizontal isothermal cylinders arranged in vertical and inclined arrays. The effects of the vertical separation spacing to the cylinder diameter ratio (Py/d), horizontal separation spacing to the cylinder diameter ratio (Px/d) and Rayleigh number (Ra) variation on the average heat transfer from the arrays are considered via this prediction. The training data for optimizing the ANN structure is based on available experimental data. The Levenberg-Marquardt back propagation algorithm is used for ANN training. The proposed ANN is developed using MATLAB functions. For the best ANN structure obtained in this investigation, the mean relative errors of 0.027% and 0.482% were reached for the training and test data, respectively. The results show that the predicted values are very close to the experimental ones.

Źródło:

Polish Journal of Chemical Technology; 2012, 14, 4; 46-52
1509-8117
1899-4741

Pojawia się w:

Polish Journal of Chemical Technology

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 42.

Tytuł:

Convection and radiation cooling of overhead power lines - laboratory verification using thermography

Autorzy:

Chatzipanagiotou, P.
Felczak, M.
De Mey, G.
Chatziathanasiou, V.
Więcek, B.

Powiązania:

https://bibliotekanauki.pl/articles/114618.pdf

Data publikacji:

2017

Wydawca:

Stowarzyszenie Inżynierów i Techników Mechaników Polskich

Tematy:

overhead power line
convection
laminar and turbulent airflow
radiation
IR thermography

Opis:

The thermal behavior of overhead power lines depends upon physical parameters, such as surface emissivity and line dimensions, as well as weather conditions. In this paper, the results of the convection and radiation cooling of a conductor that simulate a power line are presented. Laboratory experiments were conducted and the results were compared with the data obtained using empirical formulae from the literature. Both the laminar and the turbulent airflow were investigated.

Źródło:

Measurement Automation Monitoring; 2017, 63, 3; 107-110
2450-2855

Pojawia się w:

Measurement Automation Monitoring

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 43.

Tytuł:

Badanie konwekcji swobodnej z powierzchni pionowego walca w środowisku hiperbarycznym
Experimental investigation of natural convection from vertical cylinder in the hyperbaric environment

Autorzy:

Majchrzycka, A.

Powiązania:

https://bibliotekanauki.pl/articles/366405.pdf

Data publikacji:

2010

Wydawca:

Polskie Towarzystwo Medycyny i Techniki Hiperbarycznej

Tematy:

konwekcja swobodna
pionowy walec
hel
natural convection
vertical cylinder
helium

Opis:

W pracy przedstawiono badania, dotyczące konwekcji swobodnej z powierzchni pionowego walca odwzorowującego sylwetkę nurka o zmiennym wydatku energetycznym. Badania wykonano w helu o ciśnieniu p = 0,5-5MPa, a wyniki przedstawiono postaci równania kryterialnego Nu = f(Ra) oraz korelacji, która umożliwia obliczenie współczynnika przejmowania ciepła w funkcji ciśnienia gazu i symulowanego wydatku energetycznego nurka.
The paper reports experimental investigation of natural convection from vertical cylinder that simulates the diver’s body of the different activity level. Experiments were carried out in the hyperbaric helium at absolute pressure range of p=0,5-5 MPa. The results are given as the correlation Nu = f(Ra) and correlation between convective heat transfer coefficient from the outer surface of vertical cylinder, pressure and simulated activity level.

Źródło:

Polish Hyperbaric Research; 2010, 1(30); 13-24
1734-7009
2084-0535

Pojawia się w:

Polish Hyperbaric Research

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 44.

Tytuł:

Analysis of the occurrence of natural convection in a bed of bars in vertical temperature gradient conditions

Autorzy:

Wyczółkowski, R.
Musiał, D.

Powiązania:

https://bibliotekanauki.pl/articles/239971.pdf

Data publikacji:

2013

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

natural convection
bed of bars
porous material
konwekcja naturalna
złoża prętów
materiały porowate

Opis:

The reason for undertaking this study was to determine the possible involvement of natural convection in the global heat transfer, that occurs in the heated steel rods bed. This problem is related to the setting of the effective thermal conductivity of the bars bed. This value is one of the boundary conditions for heating modeling of steel rods bundles during heat treatment. The aim of this study was to determine for which geometry of the bed bars, there will be no free convection. To analyze the problem the Rayleigh criterion was used. It was assumed that for the value of the number Ra < 1700 convection in the bed bars does not occur. For analysis, the results of measurements of the temperature distribution in the unidirectionally heated beds of bars were used. It has been shown, that for obtained, during the test, differences of temperature between the surfaces of adjacent rods, convection can occur only when the diameter of the rod exceeds 18 mm.

Źródło:

Archives of Thermodynamics; 2013, 34, 1; 71-83
1231-0956
2083-6023

Pojawia się w:

Archives of Thermodynamics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 45.

Tytuł:

Wyznaczanie gęstości strumienia ciepła konwekcji wymuszonej w przepływie laminarnym w przewodach prostoosiowych metodą elementów brzegowych
Determination of heat flux density of forced convection flows through straight pipes by the Boundary Element Method

Autorzy:

Teleszewski, T. J.

Powiązania:

https://bibliotekanauki.pl/articles/404095.pdf

Data publikacji:

2014

Wydawca:

Polskie Towarzystwo Symulacji Komputerowej

Tematy:

metoda elementów brzegowych
laminarny przepływ jednokierunkowy
strumień ciepła
konwekcja
konwekcja wymuszona
boundary element method
laminar unidirectional flow
heat flux
convection
forced convection

Opis:

W pracy przedstawiono algorytm MEB do analizy pól temperatury i gęstości strumienia ciepła przy przepływie laminamym z wymianą ciepła w przewodach prostoosiowych o dowolnym kształcie przekroju poprzecznego. Zaprezentowano sformułowanie zagadnienia przy użyciu metody elementów brzegowych do opisu przepływu i wymiany ciepła w przepływie jednokierunkowym przez przewód o dowolnym kształcie przekroju poprzecznego. Przedstawiono graficzne rezultaty obliczeń przepływu z udziałem konwekcji wymuszonej w profilowanym przewodzie prostoosiowym.
The paper presents the numerical application Boundary Element Method to analyze the temperature and heat flux density distribution of forced convection laminar flows through straight pipes with arbitrary cross-section shapes. Integral formulations the problems of the fluid flow and heat exchange for the case of the laminar unidirectional flow with heat transfer was presented. Moreover graphical results of the numerical calculations the velocity, temperature and heat flux of laminar flow in the profiled straight pipe were presented.

Źródło:

Symulacja w Badaniach i Rozwoju; 2014, 5, 2; 143-153
2081-6154

Pojawia się w:

Symulacja w Badaniach i Rozwoju

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 46.

Tytuł:

Effect of radial fins on natural convection between horizontal circular and square cylinders

Autorzy:

Jafari, I.
Mahdavy-Moghadam, H.
Taeibi-Rahni, M.
Dayyan, M.
Seyyedi, S. M.

Powiązania:

https://bibliotekanauki.pl/articles/279844.pdf

Data publikacji:

2014

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

radial fins
natural convection
lattice Boltzmann method
horizontal annulus

Opis:

In this paper, the effects of the number and arrangement of radial fins on laminar natural co- nvection between horizontal circular and square cylinders has been investigated numerically with the lattice Boltzmann method. The Rayleigh number is varied from Ra = 10³ − 10⁶), the number of fins (N = 2 − 8) and the Prandtl number (Pr = 0.7). The local Nusselt number profiles over the outer and inner cylinders and the average Nusselt number over the top, bottom and side walls of the outer cold square cylinder are obtained. The temperature and streamline contours are also depicted to investigate the heat and fluid flow behavior inside the computational domain.

Źródło:

Journal of Theoretical and Applied Mechanics; 2014, 52, 3; 827-837
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 47.

Tytuł:

Konwekcyjne suszenie wybranych serów podpuszczkowych twardych
Convection drying of selected hard renner cheeses

Autorzy:

Mazur, J.
Grochowicz, J.
Panasiewicz, M.
Sobczak, P.
Zawiślak, K.

Powiązania:

https://bibliotekanauki.pl/articles/291097.pdf

Data publikacji:

2005

Wydawca:

Polskie Towarzystwo Inżynierii Rolniczej

Tematy:

suszenie konwekcyjne
ser żółty
cele przyprawowe
convection drying
hard cheese
flavouring purposes

Opis:

W pracy przedstawiono wyniki badań nad konewkcyjnym suszeniem wybranych twardych serów żółtych na cele przyprawowe. Procesowi suszenia poddawano rodrobnione na rozdrabniaczu tarczowym (o wymiarach oczek Ø 4 i 6 mm) sery („Parmezan”, „Gouda”, „Edamski”) przy temperaturze powietrza suszącego 30°C i prędkości przepływu powietrza 3 m/s.
Paper presented the results of study on convection drying of selected hard yellow cheeses for flavouring purposes. The cheeses (Gouda, Parmezan, Edamer) ground in a disc rasping machine (hole diameters 4 and 6 mm) were dried by forced convection at the air temperature 30 deg C and flow velocity 3 m/s.

Źródło:

Inżynieria Rolnicza; 2005, R. 9, nr 11, 11; 309-316
1429-7264

Pojawia się w:

Inżynieria Rolnicza

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 48.

Tytuł:

MHD forced convection using ferrofluid over a backward facing step containing a finned cylinder

Autorzy:

Toumi, Meriem
Bouzit, Mohamed
Bouzit, Fayçal
Mokhefi, Abderrahim

Powiązania:

https://bibliotekanauki.pl/articles/2106228.pdf

Data publikacji:

2022

Wydawca:

Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej

Tematy:

fin positions
forced convection
nanoparticles
heat transfer
finned cylinder
magnetohydrodynamic
backward facing step

Opis:

In this paper, a numerical study of forced convection on a backward facing step containing a single-finned fixed cylinder has been performed, using a ferrofluid and external magnetic field with different inclinations. The partial differential equations, which determine the conservation equations for mass, momentum and energy, were solved using the finite element scheme based on Galerkin’s method. The analysis of heat transfer characteristics by forced convection was made by taking different values of the Reynolds number (Re between 10 and 100), Hartmann number (Ha between 0 and 100), nanoparticles concentration (φ between 0 and 0.1) and magnetic field inclination (γ between 0° and 90°); also, several fin positions α [0°–180°] were taken in the counter clockwise direction by a step of 5. After analysing the results, we concluded that Hartmann number, nanoparticles concentration, Reynolds number and magnetic field angles have an influence on the heat transfer rate. However, the fin position on the cylinder has a big impact on the Nusselt number and therefore on heat transfer quality. The best position of the fin is at (α = 150°), which gives the best Nusselt number and therefore the best heat trans-fer, but the fin position at (α = 0°) remains an unfavourable case that gives the lowest Nusselt values.

Źródło:

Acta Mechanica et Automatica; 2022, 16, 1; 70--81
1898-4088
2300-5319

Pojawia się w:

Acta Mechanica et Automatica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 49.

Tytuł:

Stabilized Galerkin finite element methods for convection dominated and incompressible flow problems

Autorzy:

Lube, Gert

Powiązania:

https://bibliotekanauki.pl/articles/1361057.pdf

Data publikacji:

1994

Wydawca:

Polska Akademia Nauk. Instytut Matematyczny PAN

Opis:

In this paper, we analyze a class of stabilized finite element formulations used in computation of (i) second order elliptic boundary value problems (diffusion-convection-reaction model) and (ii) the Navier-Stokes problem (incompressible flow model). These stabilization techniques prevent numerical instabilities that might be generated by dominant convection/reaction terms in (i), (ii) or by inappropriate combinations of velocity/pressure interpolation functions in (ii). Stability and convergence results on non-uniform meshes are given in the whole range from diffusion to convection/reaction dominated situations. In particular, we recover results for the streamline upwind and Galerkin/least-squares methods. Numerical results are presented for low order interpolation functions.

Źródło:

Banach Center Publications; 1994, 29, 1; 85-104
0137-6934

Pojawia się w:

Banach Center Publications

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 50.

Tytuł:

The onset of convection in a rotating multicomponent fluid layer

Autorzy:

Prakash, J.
Singh, V.
Kumar, R.
Kumari, K.

Powiązania:

https://bibliotekanauki.pl/articles/281283.pdf

Data publikacji:

2016

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

multicomponent convection
principle of exchange of stabilities
oscillatory motions
complex growth rate
concentration Rayleigh number
Lewis number

Opis:

The onset of convective instability is analysed in a rotating multicomponent fluid layer in which density depends on n stratifying agents (one of them is heat) having different diffusivities. Two problems have been analysed mathematically. In the first problem, a sufficient condition is derived for the validity of the principle of the exchange of stabilities. Further, when the complement of this condition holds good, oscillatory motions of neutral or growing amplitude can exist, and thus it is important to derive upper bounds for the complex growth rate of such motions when at least one of the bounding surfaces is rigid so that exact solutions of the problem in closed form are not obtainable. Thus, as the second problem, bounds for the complex growth rates are also obtained. Above results are uniformly valid for quite general nature of the bounding surfaces.

Źródło:

Journal of Theoretical and Applied Mechanics; 2016, 54, 2; 477-488
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 51.

Tytuł:

Effect of slip condition on viscoelastic MHD oscillatory forced convection flow in a vertical channel with heat radiation

Autorzy:

Singh, K. D.

Powiązania:

https://bibliotekanauki.pl/articles/955264.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

magnetohydrodynamika
konwekcja wymuszona
lepkosprężystość
porowatość
oscillatory
MHD
forced convection
viscoelastic
slip flow
porous medium

Opis:

In this paper an oscillatory flow of a viscoelastic, incompressible and electrically conducting fluid through a porous medium bounded by two infinite vertical parallel plates is discussed. One of these plates is subjected to a slip-flow condition and the other to a no-slip condition. The pressure gradient in the channel oscillates with time. A magnetic field of uniform strength is applied in the direction perpendicular to the plates. The induced magnetic field is neglected due to the assumption of a small magnetic Reynolds number. The temperature difference of the two plates is also assumed high enough to induce heat transfer due to radiation. A closed form analytical solution to the problem is obtained. The analytical results are evaluated numerically and then presented graphically to discuss in detail the effects of different parameters entering into the problem. A number of particular cases have been shown by dotted curves in the figures. During the analysis it is found that the physical and the mathematical formulations of the problems by Makinde and Mhone (2005), Mehmood and Ali (2007), Kumar et al. (2010) and Choudhury and Das (2012) are not correct. The correct solutions to all these important oscillatory flow problems are deduced.

Źródło:

International Journal of Applied Mechanics and Engineering; 2013, 18, 4; 1237-1248
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 52.

Tytuł:

An analysis of thermo-magnetic convection of paramagnetic fluid in rectangular enclosure

Autorzy:

Kraszewska, A.
Pyrda, Ł.

Powiązania:

https://bibliotekanauki.pl/articles/105828.pdf

Data publikacji:

2016

Wydawca:

Centrum Badań i Innowacji Pro-Akademia

Tematy:

thermo-magnetic convection
strong magnetic field
experimental analysis
paramagnetic fluid
konwekcja termo-magnetyczna
silne pole magnetyczne
analiza eksperymentalna
ciecz paramagnetyczna

Opis:

The thermo-magnetic convection of paramagnetic fluid in a strong magnetic field is studied. The fluid is aqueous solution of glycerol with gadolinium nitrate hexahydrate. Experimental enclosure – rectangular vessel with aspect ratio equal to 2 – was heated from the bottom, and cooled from the top. Temperature difference between top and bottom walls was kept constant ΔT=5K. The magnetic induction was increased stepwise from 1 to 10 [T]. On the basis of temperature measurements, analysis of heat transfer and fluid flow were performed, showing that magnetic field strongly enhance heat transfer (over 300%) and that aspect ratio of the enclosure has a great influence on heat exchange in the system.

Źródło:

Acta Innovations; 2016, 18; 5-13
2300-5599

Pojawia się w:

Acta Innovations

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 53.

Tytuł:

Linear stability effect of densely distributed porous medium and Coriolis force on Soret driven ferrothermohaline convection

Autorzy:

Sekar, R.
Murugan, D.

Powiązania:

https://bibliotekanauki.pl/articles/264456.pdf

Data publikacji:

2018

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

siła Coriolisa
model Darcy'ego
efekt Soreta
ferrofluid
Coriolis force
Darcy model
Soret effect
thermohaline convection

Opis:

The effect of Coriolis force on the Soret driven ferrothermohaline convection in a densely packed porous medium has been studied. A linear stability analysis is carried out using normal mode technique. It is found that stationary convection is favorable for the Darcy model, therefore oscillatory instability is studied. A small thermal perturbation is applied to the basic state and linear stability analysis is used for which the normal mode technique is applied. It is found that the presence of a porous medium favours the onset of convection. The porous medium is assumed to be variable and the effect of the permeable parameter is to destabilize the system. The present work has been carried out both for oscillatory as well as stationary instabilities. The results are depicted graphically.

Źródło:

International Journal of Applied Mechanics and Engineering; 2018, 23, 4; 911-928
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 54.

Tytuł:

Lattice Boltzmann simulation of natural convection flow around a horizontal cylinder located beneath an insulation plate

Autorzy:

Mehrizi, A. A.
Farhadi, M.
Afrouzi, H. H.
Shayamehr, S.
Lotfizadeh, H.

Powiązania:

https://bibliotekanauki.pl/articles/949135.pdf

Data publikacji:

2013

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

free convection
isothermal cylinder
Lattice Boltzmann method (LBM)

Opis:

In this paper, two-dimensional heat transfer solution of natural convection around an isothermal cylinder located beneath an insulation wall is studied. The effects of distance ratio of the cylinder to the wall as well as the impact of the dimensionless Rayleigh number in the flow and heat transfer are taken into account. Solving the flow equations for L/D ratio with values 0.5, 0.7, and 1.5 and the Rayleigh number ranging from 1000 to 40000 is carried out. The results are compared with the experimental data which present a good agreement. The results indicate that the effect of weakened natural convection flow in the cylinder commences when decreasing L/D ratio from the value 1.5 to 0.5 leading to a decline in heat transfer and the Nusselt number. This process occurs in all values of the Rayleigh number. For the ratio number greater than 1.5, the impact of adiabatic wall is neglected, and there is no significant influence on the natural convection flow. Increasing the angle from 0◦to180◦results in a fall in the Nusselt number which is as a consequence of growth in the distances of isothermal lines.

Źródło:

Journal of Theoretical and Applied Mechanics; 2013, 51, 3; 729-739
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 55.

Tytuł:

Boundary effects on electrothermal convection in a dielectric fluid layer

Autorzy:

Ravisha, M.
Raghunatha, K. R.
Mamatha, A. L.
Shivakumara, I. S.

Powiązania:

https://bibliotekanauki.pl/articles/240648.pdf

Data publikacji:

2019

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

boundary effect
dielectric fluid
AC electric field
thermal convection
konwekcja termiczna
płyn dielektryczny
warunki brzegowe

Opis:

The instability characteristics of a dielectric fluid layer heated from below under the influence of a uniform vertical alternating current (AC) electric field is analyzed for different types of electric potential (constant electric potential/ electric current), velocity (rigid/free) and temperature boundary conditions (constant temperature/heat flux or a mixed condition at the upper boundary). The resulting eigenvalue problem is solved numerically using the shooting method for various boundary conditions and the solution is also found in a simple closed form when the perturbation heat flux is zero at the boundaries. The possibility of a more precise control of electrothermal convection (ETC) through various boundary conditions is emphasized. The effect of increasing AC electric Rayleigh number is to hasten while that of Biot number is to delay the onset of ETC. The system is more stable for rigid-rigid boundaries when compared to rigid-free and least stable for free-free boundaries. The change of electric potential boundary condition at the upper boundary from constant electric potential to constant electric current is found to instill more stability on the system.

Źródło:

Archives of Thermodynamics; 2019, 40, 1; 3-19
1231-0956
2083-6023

Pojawia się w:

Archives of Thermodynamics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 56.

Tytuł:

Wpływ suszenia konwekcyjnego na wybrane cechy mechaniczne i reologiczne korzenia pietruszki
The impact of convection drying on selected mechanical and rheological properties of parsley root

Autorzy:

Stępień, B.

Powiązania:

https://bibliotekanauki.pl/articles/292150.pdf

Data publikacji:

2008

Wydawca:

Polskie Towarzystwo Inżynierii Rolniczej

Tematy:

pietruszka
suszenie konwekcyjne
wytrzymałość
reologia
parsley
convection drying
strength
rheology

Opis:

Wykonano badania ściskania, przecinania oraz relaksacji naprężeń dla korzenia pietruszki suszonej konwekcyjnie. Surowiec blanszowano i odwodniono osmotycznie przed suszeniem. Dla porównania cechy mechaniczne i reologiczne wyznaczono dla produktu uzyskanego bezpośrednio po suszeniu oraz po 18 miesiącach próżniowego przechowywania suszu. Suszenie konwekcyjne istotnie obniża wytrzymałość na ściskanie suszu i materiału uwodnionego. Blanszowanie pietruszki przed suszeniem konwekcyjnym zwiększa wytrzymałość suszu na przecinanie w stosunku do wytrzymałości surowca oraz produktów uzyskanych z pietruszki nie poddanej obróbce i odwodnionej osmotycznie. Zabieg ten powoduje również wzrost podatność pietruszki na deformacje struktury komórkowej w trakcie suszenia.
The scope of the research included tests of compression, cutting and stress relaxation for parsley root dried by convection. Raw material was blanched and dehydrated by osmosis before drying. For comparison, mechanical and rheological properties were determined for product obtained directly after drying, and after 18 months of dried material storage in vacuum conditions. Convection drying significantly reduces compression strength of dried material and hydrated material. Parsley blanching before convection drying increases dried material resistance to cutting as compared to strength of raw material and products obtained from unprocessed and dehydrated by osmosis parsley. This treatment also increases parsley susceptibility to cellular structure deformations during drying.

Źródło:

Inżynieria Rolnicza; 2008, R. 12, nr 5(103), 5(103); 267-274
1429-7264

Pojawia się w:

Inżynieria Rolnicza

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 57.

Tytuł:

The natural convection inside a 3D triangular cross section cavity filled with nanofluid and included cylinder with different arrangements

Autorzy:

Ghoben, Zainab Kareem
Hussein, Ahmed Kadhim

Powiązania:

https://bibliotekanauki.pl/articles/2096184.pdf

Data publikacji:

2022

Wydawca:

Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN

Tematy:

natural convection
triangular cavity
inner cylinder
nanofluid
3D
konwekcja naturalna

Opis:

In this paper the laminar unsteady natural convection heat transfer of (Al2O3-water) nanofluid inside 3D triangular cross section cavity was investigated. The cavity was heated differentially, the vertical walls were kept at different constant temperatures. The left hot and the right cold. The effect of the solid volume fraction was examined for two values and compared with the pure water results. The (Ra) range studied was (103≤Ra≤106). Inserting cylindrical body inside the cavity also investigated in three cases. One concentric cylinder has radius (15%) of the cavity side length. The other cases were of two cylinders having radius (7.5%) of the cavity side length, aligned vertically or nonaligned. The results show that the higher solid volume fraction gives the maximum enhancement of the average (Nu) and this enhancement increases with (Ra) increase. For the cases with inner cylinders, the average (Nu) enhanced for the case of double cylinders over single cylinder. On other hand, the nonaligned position of the cylinders giving more enhancement than other position. As like as, the location of maximum horizontal or vertical velocities were varied with the cylinders position while (Ra) has no effect.

Źródło:

Diagnostyka; 2022, 23, 2; no. art. 2022205
1641-6414
2449-5220

Pojawia się w:

Diagnostyka

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 58.

Tytuł:

Mixed convection heat transfer of a nanofluid in a square ventilated cavity separated horizontally by a porous layer and discrete heat source

Autorzy:

Messaoud, Hamdi
Adel, Sahi
Ouerdia, Ourrad

Powiązania:

https://bibliotekanauki.pl/articles/27312228.pdf

Data publikacji:

2023

Wydawca:

Polska Akademia Nauk. Czasopisma i Monografie PAN

Tematy:

mixed convection
vented cavity
porous layer
finite volume method

Opis:

Laminar mixed convection heat transfer in a vented square cavity separated by a porous layer filled with different nanofluids (Fe3O4, Cu, Ag and Al2O3) has been investigated numerically. The governing equations of mixed convection flow for a Newtonian nanofluid are assumed to be two-dimensional, steady and laminar. These equations are solved numerically by using the finite volume technique. The effects of significant parameters such as the Reynolds number (10 ≤ Re ≤ 1000), Grashof number (103 ≤ Gr ≤ 106 ), nanoparticle volume fraction (0.1 ≤ φ ≤ 0.6), porous layer thickness (0 ≤ γ ≤ 1) and porous layer position (0.1 ≤ δ ≤ 0.9) are studied. Numerical simulation details are visualized in terms of streamline, isotherm contours, and average Nusselt number along the heated source. It has been shown that variations in Reynolds and Darcy numbers have an impact on the flow pattern and heat transfer within a cavity. For higher Reynolds (Re > 100), Grashof (Gr > 105 ) numbers and nanoparticles volume fractions the heat transfer rate is enhanced and it is optimal at lower values of Darcy number (Da = 10−5 ). In addition, it is noticed that the porous layer thickness and location have a significant effect on the control of the heat transfer rate inside the cavity. Furthermore, it is worth noticing that Ag nanoparticles presented the largest heated transfer rate compared to other nanoparticles.

Źródło:

Archives of Thermodynamics; 2023, 44, 2; 87--114
1231-0956
2083-6023

Pojawia się w:

Archives of Thermodynamics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 59.

Tytuł:

Wpływ wstępnego odwadniania osmotycznego na współczynnik dyfuzji wody w tkance jabłek suszonych konwekcyjnie
Diffusivity of osmotic-convection dried plant tissue

Autorzy:

Janowicz, M.
Lenart, A.

Powiązania:

https://bibliotekanauki.pl/articles/289562.pdf

Data publikacji:

2005

Wydawca:

Polskie Towarzystwo Inżynierii Rolniczej

Tematy:

jabłka
dyfuzja
suszenie konwekcyjne
odwadnianie osmotyczne
apples
water diffusion
convection drying
osmotic dehydration

Opis:

Celem pracy jest analiza wpływu odwadniania osmotycznego, rodzaju substancji osmotycznej oraz temperatury i czasu odwadniania na dyfuzję wody w tkance jabłek w czasie suszenia konwekcyjnego. Stwierdzono, że średni umowny współczynnik dyfuzji wody jabłek w czasie suszenia konwekcyjnego wzrasta wraz z podwyższaniem temperatury suszenia, bez względu na zastosowana substancję osmotyczną. Czas odwadniania osmotycznego wpływa istotnie na wartość umownego współczynnika dyfuzji wody w czasie suszenia jabłek.
The aim of study was to analyze the influence of osmotic dehydration, kind of osmotic substance, temperature and time of dehydration of water diffusion in apple tissue during convection drying. It was found that the apparent water diffusion coefficient of apple tissue increased simultaneously with rising of drying temperature, irrespective of osmotic substance used at convection drying. The time of osmotic dehydration affected significantly the value of apparent water diffusion coefficient during drying of the apples.

Źródło:

Inżynieria Rolnicza; 2005, R. 9, nr 11, 11; 191-199
1429-7264

Pojawia się w:

Inżynieria Rolnicza

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 60.

Tytuł:

Natural convection heat transfer in heated vertical tubes with internal rings

Autorzy:

Nayak, R. C.
Roul, M. K.
Sarangi, S. K.

Powiązania:

https://bibliotekanauki.pl/articles/240303.pdf

Data publikacji:

2018

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

heat flux
heat transfer
natural convection
ring spacing
ring thickness
strumień cieplny
wymiana ciepła
konwekcja naturalna
pierścień

Opis:

Experimental investigation of natural convection heat transfer in heated vertical tubes dissipating heat from the internal surface is presented. The test section is electrically heated and constant wall heat flux is maintained both circumferentially and axially. Four different test sections are taken having 45 mm internal diameter and 3.8 mm thickness. The length of the test sections are 450 mm, 550 mm, 700 mm and 850 mm. Ratios of length to diameter of the test sections are taken as 10, 12.22, 15.56, and 18.89. Wall heat fluxes are maintained at 250–3341 W/m2 . Experiments are also conducted on channels with internal rings of rectangular section placed at various distances. Thickness of the rings are taken as 4 mm, 6 mm, and 8 mm. The step size of the rings varies from 75 mm to 283.3 mm. The nondimensional ring spacing, expressed as the ratios of step size to diameter, are taken from 1.67 to 6.29 and the non-dimensional ring thickness, expressed as the ratios of ring thickness to diameter are taken from 0.089 to 0.178. The ratios of ring spacing to its thickness are taken as 9.375 to 70.82. The effects of various parameters such as length to diameter ratio, wall heat flux, ring thickness and ring spacing on local steady-state heat transfer behavior are observed. From the experimental data a correlation is developed for average Nusselt number and modified Rayleigh number. Another correlation is also developed for modified Rayleigh number and modified Reynolds number. These correlations can predict the data accurately within ±10% error.

Źródło:

Archives of Thermodynamics; 2018, 39, 4; 85--111
1231-0956
2083-6023

Pojawia się w:

Archives of Thermodynamics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 61.

Tytuł:

Double-diffusive convection of synovial (couple-stress) fluid in the presence of Hall current through a porous medium

Autorzy:

Singh, M.

Powiązania:

https://bibliotekanauki.pl/articles/264478.pdf

Data publikacji:

2018

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

płyn maziowy
materiały porowate
zjawisko Halla
double diffusive convection
porous medium and Hall current
compressibility
synovial fluid

Opis:

An investigation made on the effect of Hall currents on double-diffusive convection of a compressible synovial (couple-stress) fluid in the presence of a horizontal magnetic field through a porous layer is considered. The analysis is carried out within the framework of linear stability theory and normal mode technique. A dispersion relation governing the effects of viscoelasticity, compressibility, magnetic field and porous layer is derived. For the stationary convection, a synovial fluid behaves like an ordinary Newtonian fluid due to the vanishing of the viscoelastic parameter. The stable-solute gradient, compressibility, and magnetic field have postponed the onset of convection, whereas Hall currents and medium permeability have not postponed the onset of convection, moreover, a synovial fluid has a dual character in the presence of Hall currents, whereas in the absence of Hall current in synovial fluid have postponed the onset of convection, which is in contrast in case of thermal convection couple-stress fluid with same effects. These analytic results are confirmed numerically and the effects of various parameters are depicted graphically. It has been observed that oscillatory modes are introduced due to the presence of viscoelasticity, magnetic field, porous medium and Hall currents which were non- existent in their absence. The sufficient conditions for the non-existence of overstability are also obtained.

Źródło:

International Journal of Applied Mechanics and Engineering; 2018, 23, 4; 963-976
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 62.

Tytuł:

Conjugate heat and mass transfer on fluctuating mixed convection flow along a vertical wedge with thermal radiation

Autorzy:

Firoza, M. N.
Roy, N. C.
Hossain, A.

Powiązania:

https://bibliotekanauki.pl/articles/264573.pdf

Data publikacji:

2017

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

mixed convection
thermal radiation
vertical wedge
promieniowanie cieplne
przepływ ciepła
niska częstotliwość

Opis:

We study the boundary layer characteristics of heat and mass transfer flow past a vertical wedge in the presence of thermal radiation. The surface temperature and the species concentration are assumed to be oscillating in the magnitude but not in the direction of oncoming flow velocity. The governing equations have been solved by two distinct methods, namely, the straightforward finite difference method for the entire frequency range, and the series solution for the low frequency range and the asymptotic series expansion method for the high frequency range. Numerical solutions have been presented in terms of the amplitudes and phase angles of the skin friction, the rate of heat transfer and the mass transfer with the variations of Richardson’s number, the Prandtl number, the conduction–radiation parameter, the surface temperature parameter and the Schmidt number. Furthermore, the effects of these parameters are examined in terms of the transient skin friction, heat transfer and mass transfer.

Źródło:

International Journal of Applied Mechanics and Engineering; 2017, 22, 3; 539-565
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 63.

Tytuł:

Numerical solution of non-Newtonian fluids flow past an accelerated vertical infinite plate in the presence of free convection currents

Autorzy:

Patel, M.
Timol, M. G.

Powiązania:

https://bibliotekanauki.pl/articles/265022.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

płyn nienewtonowski
analiza podobieństwa
prąd
non-Newtonian fluids
convection currents
similarity analysis

Opis:

A similarity analysis of non-Newtonian fluid flow past an accelerated vertical infinite plate in the presence of free convection current is carried out. A group theoretic generalized dimensional analysis is employed to achieve the governing non-linear ordinary differential equations in the most general form. Numerical solutions of these equations are given with the plot of their velocity profiles with the effects of Pr-Prandtl number and Gr-Grashof number.

Źródło:

International Journal of Applied Mechanics and Engineering; 2013, 18, 3; 761-777
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 64.

Tytuł:

Combined effects of helical force and rotation on stationary convection of a binary ferrofluid in a porous medium

Autorzy:

Kpossa, M.
Monwanou, A. V.

Powiązania:

https://bibliotekanauki.pl/articles/2174187.pdf

Data publikacji:

2022

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja
ferrofluid
ośrodek porowaty
helical force
stationary convection
binary mixture of ferrofluid
porous medium
rotation

Opis:

This work studies the simultaneous effects of helical force, rotation and porosity on the appearance of stationary convection in a binary mixture of a ferrofluid and on the size of convection cells. We have determined the analytical expression of the Rayleigh number of the system as a function of the dimensionless parameters. The effect of each parameter on the system is studied. The consideration of the simultaneous effect of the basic characteristics made it possible to determine the evolution of the convection threshold in the ferrofluid and then the size of convection cells. The analyzes of the various results obtained allowed us to deduce whether the convection sets in quickly or with a delay when the various effects taken into account in the study are considered simultaneously.

Źródło:

International Journal of Applied Mechanics and Engineering; 2022, 27, 2; 158--176
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 65.

Tytuł:

Non-parallel plane Rayleigh Benard convection in cylindrical geometry

Autorzy:

Golbabai, A.

Powiązania:

https://bibliotekanauki.pl/articles/1340378.pdf

Data publikacji:

1995

Wydawca:

Polska Akademia Nauk. Instytut Matematyczny PAN

Tematy:

inner solution
perturbed wall

Opis:

This paper considers the effect of a perturbed wall in regard to the classical Benard convection problem in which the lower rigid surface is of the form $z=ε^2 g(s)$, s=ε r, in axisymmetric cylindrical polar coordinates (r,ϕ,z). The boundary conditions at s=0 for the linear amplitude equation are found and it is shown that these conditions are different from those which apply to the nonlinear problem investigated by Brown and Stewartson [1], representing the distribution of convection cells near the center.

Źródło:

Applicationes Mathematicae; 1995-1996, 23, 1; 25-36
1233-7234

Pojawia się w:

Applicationes Mathematicae

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 66.

Tytuł:

Monotone iterative methods for infinite systems of reaction-diffusion-convection equations with functional dependence

Autorzy:

Brzychczy, S.

Powiązania:

https://bibliotekanauki.pl/articles/255097.pdf

Data publikacji:

2005

Wydawca:

Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH

Tematy:

infinite systems
reaction-diffusion-convection equations
semilinear parabolic differential-functional equations
Volterra functionals
monotone iterative methods
method of upper and lower solutions

Opis:

We consider the Fourier first initial-boundary value problem for an infinite system of semilinear parabolic differential-functional equations of reaction-diffusion-convection type of the form [formula] where [formula] in a bounded cylindrical domain (0, T] x G := D rcup Rm+1. The right-hand sides of the system are Volterra type functionals of the unknown function z. In the paper, we give methods of the construction of the monotone iterative sequences converging to the unique classical solution of the problem considered in partially ordered Banach spaces with various convergence rates of iterations. We also give remarks on monotone iterative methods in connection with numerical methods, remarks on methods for the construction of lower and upper solutions and remarks concerning the possibility of extending these methods to more general parabolic equations. All monotone iterative methods are based on differential inequalities and, in this paper, we use the theorem on weak partial differential-functional inequalities for infinite systems of parabolic equations, the comparison theorem and the maximum principle. A part of the paper is based on the results of our previous papers. These results generalize the results obtained by several authors in numerous papers for finite systems of semilinear parabolic differential equations to encompass the case of infinite systems of semilinear parabolic differential-functional equations. The monotone iterative schemes can be used for the computation of numerical solutions.

Źródło:

Opuscula Mathematica; 2005, 25, 1; 29-99
1232-9274
2300-6919

Pojawia się w:

Opuscula Mathematica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 67.

Tytuł:

Similarity solutions on mixed convection heat transfer from a horizontal surface saturated in a porous medium with internal heat generation

Autorzy:

Ferdows, M.
Liu, D.

Powiązania:

https://bibliotekanauki.pl/articles/265076.pdf

Data publikacji:

2017

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

mixed convection
horizontal porous surface
internal heat generation
konwekcja mieszana
powierzchnia porowata
wytwarzanie ciepła

Opis:

The aim of this work is to study the mixed convection boundary layer flow from a horizontal surface embedded in a porous medium with exponential decaying internal heat generation (IHG). Boundary layer equations are reduced to two ordinary differential equations for the dimensionless stream function and temperature with two parameters: ε, the mixed convection parameter, and λ, the exponent of x. This problem is numerically solved with a system of parameters using built-in codes in Maple. The influences of these parameters on velocity and temperature profiles, and the Nusselt number, are thoroughly compared and discussed.

Źródło:

International Journal of Applied Mechanics and Engineering; 2017, 22, 1; 253-258
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 68.

Tytuł:

The complex Ginzburg Landau model for an oscillatory convection in a rotating fluid layer

Autorzy:

Manjula, S. H.
Kiran, P.
Reddy, P. Raj
Bhadauria, B. S.

Powiązania:

https://bibliotekanauki.pl/articles/266148.pdf

Data publikacji:

2020

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja
teoria nieliniowa
liczba Nusselta
convection
finite amplitude
nonlinear theory
rotation modulation
Nusselt number

Opis:

A weakly nonlinear thermal instability is investigated under rotation speed modulation. Using the perturbation analysis, a nonlinear physical model is simplified to determine the convective amplitude for oscillatory mode. A non-autonomous complex Ginzburg-Landau equation for the finite amplitude of convection is derived based on a small perturbed parameter. The effect of rotation is found either to stabilize or destabilize the system. The Nusselt number is obtained numerically to present the results of heat transfer. It is found that modulation has a significant effect on heat transport for lower values of ωf while no effect for higher values. It is also found that modulation can be used alternately to control the heat transfer in the system. Further, oscillatory mode enhances heat transfer rather than stationary mode.

Źródło:

International Journal of Applied Mechanics and Engineering; 2020, 25, 1; 75-91
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 69.

Tytuł:

Thermal performance enhancement of the mixed convection between two parallel plates by using triangular ribs

Autorzy:

Jehhef, K. A.
Badawy, F. A.
Hussein, A. A.

Powiązania:

https://bibliotekanauki.pl/articles/1839881.pdf

Data publikacji:

2021

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

badanie numeryczne
konwekcja mieszana
równanie Naviera-Stokesa
numerical study
mixed convection
vertical channel
triangular rib

Opis:

This paper aims to investigate the mixed convection between two parallel plates of a vertical channel, in the presence of a triangular rib. The non-stationary Navier-Stokes equations were solved numerically in a two-dimensional formulation for the low Reynolds number for the laminar air flow regime. Six triangular ribs heat-generating elements were located equidistantly on the heated wall. The ratio of the ribs to the channel width is varied (h / H = 0.1, 0.2, 0.3 and 0.4) to study the effect of ribs height effects, the ratio of the channel width to the ribs height is fixed constant at (H / w = 2) and the ratio of the channel height to the ribs pitch is fixed at (W/p=10). The influence of the Reynolds number that ranged from 68 to 340 and the Grashof number that ranged from 6.6 ×103 to 2.6 ×104 as well as the Richardson number chosen (1.4, 0.7, 0.4 and 0.2) is studied. The numerical results are summarized and presented as the profile of the Nusselt number, the coefficient of friction, and the thermal enhancement factor. The contribution of forced and free convection to the total heat transfer is analyzed. Similar and distinctive features of the behavior of the local and averaged heat transfer with the variation of thermal gas dynamic and geometric parameters are investigated in this paper. The results showed that the Nusselt number and friction factor increased by using the attached triangular ribs, especially when using the downstream ribs. Also, the results revealed that the Nusselt number increased by increasing the ratio of the ribs to the channel width.

Źródło:

International Journal of Applied Mechanics and Engineering; 2021, 26, 2; 11-30
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 70.

Tytuł:

New model of convection based on particle approach

Autorzy:

Alda, Witold
Dzwinel, Witold
Kitowski, Jacek
Mościński, Jacek

Powiązania:

https://bibliotekanauki.pl/articles/1953480.pdf

Data publikacji:

1997

Wydawca:

Politechnika Gdańska

Opis:

A new model for thermal convection simulations using molecular dynamics (MD) approach is reported briefly. Preliminary results are presented. Development of the method is discussed in short.

Źródło:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 1997, 1, 1; 82-88
1428-6394

Pojawia się w:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 71.

Tytuł:

Numerical Analysis of Convective Heat Transfer for Selected Geometric System

Autorzy:

Orłowska, Magdalena

Powiązania:

https://bibliotekanauki.pl/articles/2174927.pdf

Data publikacji:

2022

Wydawca:

Politechnika Koszalińska. Wydawnictwo Uczelniane

Tematy:

convection
intensification
protect
environment

Opis:

The contemporary problems and issues of environmental protection refer to a large extent to problems related – generally speaking – to energy. Currently, the production processes mainly concern the combustion of energy fuels, transport – over long distances, and their use for utility purposes, e.g. engine drive or heating. These processes significantly negatively impact the environment and are magnified by their enormous intensity and size. While energy production and transport processes have been studied for many years, and their results are widely published, the issues related to the application and operation of heating devices are little known and require much observation and research. The operating indicators of heating devices are generally characterized by low values (natural convection), and their artificial increase (intensity) cannot be used due to the acoustic effects and additional (significant) investment costs. The article presents some research results on the intensification of heat flow – i.e. the thermal efficiency of flat heaters placed in a room with a specific temperature. Physical phenomena were investigated numerically by shaping the heat exchange space. The tested systems concerned a room with a free-standing heater, a heater with a vertical panel mounted in parallel, and a system with a curved bottom plate forming the so-called de Laval nozzle. Interesting results of air velocity and temperature fields and values of the heat transfer coefficient along the height of the heater were obtained. Based on the presented research, it can be concluded that the creation of convection surfaces around the heater is advisable because it affects the intensity of heat exchange, which can be increased without energy-intensive energy expenditure, i.e. in a non-mechanical way. Undoubtedly contributes positively to investment and operating costs, which is essential in environmental protection issues.

Źródło:

Rocznik Ochrona Środowiska; 2022, 24; 163--171
1506-218X

Pojawia się w:

Rocznik Ochrona Środowiska

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 72.

Tytuł:

Mixed convection on MHD flow with thermal radiation, chemical reaction and viscous dissipation embedded in a porous medium

Autorzy:

Zigta, B.

Powiązania:

https://bibliotekanauki.pl/articles/264811.pdf

Data publikacji:

2020

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja mieszana
prędkość ssania
promieniowanie cieplne
reakcja chemiczna
lepkość
mixed convection
suction velocity
thermal radiation
chemical reaction
viscous dissipation

Opis:

In this paper, a theoretical analysis has been made to study the effect of mixed convection MHD oscillatory Couette flow in a vertical parallel channel walls embedded in a porous medium in the presence of thermal radiation, chemical reaction and viscous dissipation. The channel walls are subjected to a constant suction velocity and free stream velocity is oscillating with time. The channel walls are embedded vertically in a porous medium. A magnetic field of uniform strength is applied normal to the vertical channel walls. The nonlinear and coupled partial differential equations are solved using multi parameter perturbation techniques. The effects of physical parameters, viz., the radiation absorption parameter, Prandtl number, Eckert number, dynamic viscosity, kinematic viscosity, permeability of porous medium, suction velocity, Schmidt number and chemical reaction parameter on flow variables viz., temperature, concentration and velocity profile have been studied. MATLAB code is used to analyze theoretical facts. The important results show that an increment in the radiation absorption parameter and permeability of porous medium results in an increment of the temperature profile. Moreover, an increment in the Prandtl number, Eckert number and dynamic viscosity results in a decrement of the temperature profile. An increment in suction velocity results in a decrement of the velocity profile. An increment in the Schmidt number, chemical reaction parameter and kinematic viscosity results in a decrement of the concentration profile.

Źródło:

International Journal of Applied Mechanics and Engineering; 2020, 25, 1; 219-235
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 73.

Tytuł:

Finite Different Analysis of Free Convection Flow and Heat Transfer of Casson Nanofluid over a Vertical Plate under the Influence of Thermal Radiation

Autorzy:

Sobamowo, M. G.
Okolie, A. C.

Powiązania:

https://bibliotekanauki.pl/articles/1193438.pdf

Data publikacji:

2021

Wydawca:

Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN

Tematy:

Casson fluid
Free convection
Nanoparticle
Numerical solutions
Prandtl number
Thermal radiation

Opis:

In this paper, a numerical study on free convection flow and heat transfer of Casson nanofluids over a vertical plate under the influence of thermal radiation is carried out. The governing systems of coupled nonlinear partial differential equations of the flow and heat transfer processes are converted to a system of coupled nonlinear ordinary differential equations through suitable similarity variables. The obtained ordinary differential equations are solved using finite difference method. The results of the numerical solutions are compared with the results of past works as presented in literature and good agreement was established. Also, the effects of thermal radiation; Prandtl number, nanoparticles volume-fraction, shape and type on the flow and heat transfer behaviour of various nanofluids over the flat plate are investigated. The results show that the magnitude of velocity near the plate for the Casson nanofluid parameter decreases for increasing value of the Casson parameter, while temperature increases for increase in Casson fluid parameter. Also, the thermal radiation and volume-fraction of the nanoparticles in the base fluid increase, the velocity, temperature, viscous and thermal boundary layers of the nanofluid increase. However, the velocity of the nanofluid decreases as the Prandtl number increases while the temperature of the nanofluid increases as the Prandtl number increases. The velocity of the nanofluid decreases as the volume-fraction or concentration of the nanoparticle in the base fluid increases. The study can benefit the design engineers enhancing their understanding of the phenomenon for various industrial and engineering applications.

Źródło:

World Scientific News; 2021, 157; 38-66
2392-2192

Pojawia się w:

World Scientific News

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 74.

Tytuł:

Heat transfer by natural convection from a heated square inner cylinder to its elliptical outer enclosure utilizing nanofluids

Autorzy:

Bouras, Abdelkrim
Taloub, Djedid
Driss, Zied
Debka, Siham

Powiązania:

https://bibliotekanauki.pl/articles/2174195.pdf

Data publikacji:

2022

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja naturalna
nanociecz
ułamek objętościowy
natural convection
Rayleigh number
nanofluid
volume fraction
square elliptical

Opis:

In this paper a numerical study of natural convection of stationary laminar heat transfers in a horizontal ring between a heated square inner cylinder and a cold elliptical outer cylinder is presented. A Cu-water nanofluid flows through this annular space. Different values of the Rayleigh number and volume fraction of nanoparticles are studied. The system of equations governing the problem was solved numerically by the fluent calculation code based on the finite volume method and on the Boussinesq approximation. The interior and exterior surfaces are kept at constant temperature. The study is carried out for Rayleigh numbers ranging from 310 to 510. We have studied the effects of different Rayleigh numbers and volume fraction of nanoparticles on natural convection. The results are presented as isotherms, isocurrents, and local and mean Nusselt numbers. The aim of this study is to study the influence of the thermal Rayleigh number and volume fraction of nanoparticles on the heat transfer rate.

Źródło:

International Journal of Applied Mechanics and Engineering; 2022, 27, 2; 22--34
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 75.

Tytuł:

The effect of magnetic field dependent viscosity on ferromagnetic convection in a rotating sparsely distributed porous medium - revisited

Autorzy:

Prakash, J.
Kumar, P.
Manan, S.
Sharma, K. R.

Powiązania:

https://bibliotekanauki.pl/articles/265547.pdf

Data publikacji:

2020

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

ferrofluid
konwekcja
pole magnetyczne
materiał porowaty
convection
rotation
magnetic field dependent viscosity
porous medium

Opis:

The effect of magnetic field dependent (MFD) viscosity on the thermal convection in a ferrofluid layer saturating a sparsely distributed porous medium has been investigated by using the Darcy-Brinkman model in the simultaneous presence of a uniform vertical magnetic field and a uniform vertical rotation. A correction is applied to the study of Vaidyanathan et al. [11] which is very important in order to predict the correct behavior of MFD viscosity. A linear stability analysis has been carried out for stationary modes and oscillatory modes separately. The critical wave number and critical Rayleigh number for the onset of instability, for the case of free boundaries, are determined numerically for sufficiently large values of the magnetic parameterM1 . Numerical results are obtained and are illustrated graphically. It is shown that magnetic field dependent viscosity has a destabilizing effect on the system for the case of stationary mode and a stabilizing effect for the case of oscillatory mode, whereas magnetization has a destabilizing effect.

Źródło:

International Journal of Applied Mechanics and Engineering; 2020, 25, 1; 142-158
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 76.

Tytuł:

Role of induced magnetic field on transient natural convection flow in a vertical channel: The Riemann sum approximation approach

Autorzy:

Jha, B. K.
Sani, I.

Powiązania:

https://bibliotekanauki.pl/articles/266260.pdf

Data publikacji:

2015

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

induced magnetic field
natural convection flow
Riemann-sum approximation
pole magnetyczne
przepływ konwekcyjny
twierdzenie Laplace'a

Opis:

This paper investigates the role of induced magnetic field on a transient natural convection flow of an electrically conducting, incompressible and viscous fluid in a vertical channel formed by two infinite vertical parallel plates. The transient flow formation inside the channel is due to sudden asymmetric heating of Chanel walls. The time dependent momentum, energy and magnetic induction equations are solved semi-analytically using the Laplace transform technique along with the Riemann-sum approximation method. The solutions obtained are validated by comparisons with the closed form solutions obtained for the steady states which hale been derived separately and also by the implicit finite difference method. Graphical results for the temperature, velocity, induced magnetic field, current density, and skin-friction based on the semi-analytical solutions are presented and discussed.

Źródło:

International Journal of Applied Mechanics and Engineering; 2015, 20, 1; 65-85
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 77.

Tytuł:

Two-dimensional and dynamic method of visualization of the flow characteristics in a convection boundary layer using infrared thermography

Autorzy:

Patorski, J. A.
Bauer, G. S.
Dementjev, S.

Powiązania:

https://bibliotekanauki.pl/articles/279681.pdf

Data publikacji:

2001

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

IR-thermography measurement
visualization of internal flow within convection boundary layer
heat transfer visualization

Opis:

The paper presents a two-dimensional and dynamic (2DD) method of using infrared thermography (IRT) for visualization of the cooling efficiency of a heated wall, as this method was applied in an experimental investigation. The 2DD method allows the outer surface temperature measured by an IRT device to be worked out relative to the bulk coolant-fluid temperature. This way the 2DD method makes visible the qualitative and quantitative flow characteristics within the thin contact layer at the inner surface of the wall. These flow characteristics, and more specifically, the pattern of the flow (similar to streamlines useful for the detection of dead zones) and the distribution of the temperature differences between the temperature on the wall outer surface and the bulk temperature of the coolant, determine the cooling efficiency. Finally, animated IR thermogram sequences could be generated, allowing observation of the spatial and temporal behavior of the flow/cooling behind the wall, for an example see animations in internet page (Patorski, 2000). The study of the cooling of the proton beam entry window described in this paper is a part of the development program of neutron spallation sources with liquid metal targets. The basic idea of the experiments was to use the real interacting materials (mercury as the liquid metal and steel as the window wall) and observe the cooling effects of the mercury flow on the heated wall of the hemispherical shell of the mockup window. Different geometrical configurations of the inner flow guide tubes of the flow and different pumping velocities were examined in view of finding the optimal cooling solution.
Dwuwymiarowa dynamiczna metoda wizualizacji charakterystycznych właściwości przepływu w konwekcyjnej warstwie granicznej przy użyciu termowizji. Artykuł przedstawia, na przykładzie zastosowania w badaniach doświadczalnych, dwuwymiarową dynamiczną (2DD) metodę użycia termowizji (IRT) wizualizującą efektywność chłodzenia przepływem cieczy silnie ogrzewanej ścianki zbiornika. Wykorzystanie zsynchronizowanych pomiarów: temperatury zewnętrznej powierzchni ścianki zbiornika (za pomocą IRT) oraz temperatury masy płynącej cieczy (za pomocą termoelementów (TC)), pozwoliło na wizualizację jakościowych i ilościowych zjawisk przepływu cieczy charakteryzujących efektywność chłodzenia ścianki. Do zjawisk jakościowych zaliczono tu wizualizację obrazów przepływu; w przybliżeniu obrazów lini przepływu w pobliżu ścianki, ponieważ pola temperatur w dominującym stopniu zależą od rozkładu prędkości przepływu. Obrazy takie dają możliwość wykrycia zawirowań czy tzw. "marwych" stref przepływu występujących po niewidocznej stronie nieprzeźroczystej ścianki. Do zjawisk ilościowych zaliczono wizualizację pola rozkładu wartości różnicy temperatur pomiędzy ścianką a masą płynącej cieczy; mniejsze wartości tej różnicy wskazują lepszą lokalną efektywność chłodzenia. Wartość tej różnicy temperatur może być bezpośrednio skorelowana z konwekcyjnym współczynnikiem przekazywania ciepła. Pokazanie animacji w postaci sekwencji tak specyficznie zdefiniowanych pól temperatur pozwala na geometryczno-czasową (dynamiczną) ocenę efektywności chłodzenia ścianki zbiornika dla różnych konfiguracji wewnętrznego przepływu cieczy. Dla przykładu, na stronie internetu (Patorski,2000) pokazano dwie animacje dotyczące eksperymentów omawianych w artykule. Przedstawione badania doświadczalne służą wyborowi optymalnej konfiguracji przepływu rtęci dla chłodzenia ścianki stalowego zbiornika źródła neutronów, tzw. "okna" wejścia wiązki protonów, podczas wytwarzania neutronów z jąder atomów ciężkich metali w procesie spallacji. W omawianym przypadku rtęć będzie jednocześnie wykorzystywana do wytwarzania neutronów, jak i do chłodzenia stalowej ścianki naczynia źródła neutronów. Z punktu widzenia analizy naprężeń termo-mechanicznych w ściance "okna" zbiornika źródła neutronów było koniecznym doświadczalne zbadanie charakterystyki konwekcyjnego przekazywania ciepła z użyciem przewidywanych do zastosowania materiałów (stal i rtęć), z zastosowaniem realnych kształtów i wymiarów zbiornika źródła neutronów (cylinder zakończony półkulą) oraz wewnętrznych geometrycznych i hydraulicznych warunków przepływu rtęci.

Źródło:

Journal of Theoretical and Applied Mechanics; 2001, 39, 2; 353-376
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 78.

Tytuł:

Effects of viscous dissipation and wall conduction on steady mixed convection Couette flow of heat generating / absorbing fluid

Autorzy:

Ajibade, A. O.
Umar, A. M.

Powiązania:

https://bibliotekanauki.pl/articles/264671.pdf

Data publikacji:

2019

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

strumień masy
kanał pionowy
konwekcja mieszana
mixed convection
viscous dissipation
vertical channel
boundary thickness
mass constant flux

Opis:

This article theoretically investigated mixed convection flow of heat generating/absorbing fluid in the presence of viscous dissipation and wall conduction effects. The flow is considered to be steady in a vertical channel with some boundary thickness. One of the plates is heated while the other is kept at ambient temperature. The governing flow equations were solved analytically using Homotopy Perturbation Method (HPM). The influences of the governing parameters were captured in graphs, tables and a table was constructed for validation of the work. It is worthwhile to stress that, both the velocity and temperature profiles decrease near the heated plate with an increase in boundary thickness (d) while the reverse cases were observed toward the cold plate. The velocity profile increases near the heated plate with increase in mixed convection parameter (Gre) and decreases towards the cold plate. Rate of heat transfer has been observed to decrease with increase in boundary plate thickness (d) while the critical value of (Gre) increases with growing boundary plate thickness. The study therefore established the importance of boundary plate thickness in mixed convection investigation.

Źródło:

International Journal of Applied Mechanics and Engineering; 2019, 24, 4; 12-35
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 79.

Tytuł:

Unsteady/steady natural convection flow of reactive viscous fluid in a vertical annulus

Autorzy:

Jha, B. K.
Samaila, A. K.
Ajibade, A. O.

Powiązania:

https://bibliotekanauki.pl/articles/265663.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja naturalna
lepki płyn
egzotermiczna otulina
unsteady/steady natural convection flow
reactive viscous fluid
exothermic
open ended vertical annulus

Opis:

This paper presents both analytical and numerical analyses of a fully developed unsteady/steady natural convection flow of a reactive viscous fluid in an open ended vertical annulus. Analytical expressions for velocity, temperature, skin-friction and rate of heat transfer are obtained after simplifying and solving the governing differential equations with reasonable approximations. The interesting result found in this study is that an increase in non-dimensional time (t) , increases both temperature and velocity profiles until a steady-state value is attained. Subsequent results obtained by numerical calculations show excellent agreement with analytical results.

Źródło:

International Journal of Applied Mechanics and Engineering; 2013, 18, 1; 73-83
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 80.

Tytuł:

Natural convection and radiation in a radial porous fin with variable thermal conductivity

Autorzy:

Darvishi, M. T.
Kani, F.
Gorla, R. S. R.

Powiązania:

https://bibliotekanauki.pl/articles/955178.pdf

Data publikacji:

2014

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja naturalna
promieniowanie
wydajność cieplna
metoda kolokacji
porous radial fin
natural convection
radiation
thermal performance
spectral collocation method

Opis:

In this study, the effects of radiation and convection heat transfer in a radial porous fin are considered. The geometry considered is that of a rectangular profile fin. The porous fin allows the flow to infiltrate through it and solid-fluid interaction takes place. This study is performed using Darcy’s model to formulate the heat transfer equation. The thermal conductivity is assumed to be a function of temperature. The effects of the natural convection parameter Nc , radiation parameter Nr and thermal conductivity parameter m on the dimensionless temperature distribution and heat transfer rate are discussed. The results suggest that the radiation transfers more heat than a similar model without radiation.

Źródło:

International Journal of Applied Mechanics and Engineering; 2014, 19, 1; 27-37
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 81.

Tytuł:

Modelowanie konwekcji wymuszonej w kolektorach słonecznych metodą elementów brzegowych
Simulations forced convection by the Boundary Element Method in solar thermal collector ducts

Autorzy:

Demianiuk, A.
Teleszewski, T. J.

Powiązania:

https://bibliotekanauki.pl/articles/404065.pdf

Data publikacji:

2015

Wydawca:

Polskie Towarzystwo Symulacji Komputerowej

Tematy:

metoda elementów brzegowych
konwekcja wymuszona
kolektory słoneczne
boundary element method
forced convection
solar thermal collector

Opis:

W pracy przedstawiono algorytm MEB symulacji konwekcji wymuszonej w przewodach kolektorów słonecznych. Weryfikacja metody elementów brzegowych została dokonana poprzez porównanie rezultatów obliczeń MEB ze znanym rozwiązaniem analitycznym. W opracowaniu przedstawiono graficzne rezultaty obliczeń symulacji konwekcji wymuszonej w przewodzie kolektora płaskiego o kołowym obrysie przekroju poprzecznego przewodu. W Katedrze Ciepłownictwa Politechniki Białostockiej sporządzono blok programów obliczeniowych do wyznaczania przepływu i wymiany ciepła w zaawansowanych układach hydraulicznych. (język programowania Fortran, implementacja oprogramowania w systemie dostępu zdalnego do serwera obliczeniowego w Centrum Komputerowych Sieci Rozległych Politechniki Białostockiej).
The paper presents the numerical application of Boundary Element Method for simulations of forced convection in a solar thermal collector duct. The efficiency and the credibility of proposed algorithm were verified by numerical tests. A numerical examples presented in the article describe fully developed forced convection through circular duct of flat plate collectors. The computer programs were written in Fortran programming language.

Źródło:

Symulacja w Badaniach i Rozwoju; 2015, 6, 4; 229-239
2081-6154

Pojawia się w:

Symulacja w Badaniach i Rozwoju

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 82.

Tytuł:

Effect of suspended particles on thermosolutal convection of Rivlin-Ericksen fluid in porous medium with variable gravity

Autorzy:

Aggarwal, A. K.
Dixit, D.

Powiązania:

https://bibliotekanauki.pl/articles/264370.pdf

Data publikacji:

2018

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

płyn Rivlina-Ericksena
cząstki zawieszone
materiały porowate
zmienna grawitacja
thermosolutal convection
Rivlin-Ericksen fluid
suspended particles
porous medium
varying gravity

Opis:

The thermosolutal stability of a layer of the Rivlin-Ericksen fluid in a porous medium is considered under varying gravity conditions. It is found that for stationary convection, medium permeability and suspended particles have a destabilizing/stabilizing effect when gravity increases/decreases. The stable solute gradient has a stabilizing effect on the system.

Źródło:

International Journal of Applied Mechanics and Engineering; 2018, 23, 3; 813-820
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 83.

Tytuł:

Energy stability of Benard-Darcy two-component convection of Maxwell fluid

Autorzy:

Muti, H.
Demir, H.
Siddheshwar, P. G.

Powiązania:

https://bibliotekanauki.pl/articles/265656.pdf

Data publikacji:

2013

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

stabilność energetyczna
metoda Lapunowa
lepkosprężystość
płyn Maxwell'a
relaksacja naprężeń
energy stability analysis
Lyapunov direct method
Benard-Darcy convection
viscoelastic
twocomponent Maxwell fluid
stress relaxation

Opis:

Energy stability of a horizontal layer of a two-component Maxwell fluid in a porous medium heated and salted from below is studied under the Oberbeck-Boussinesq-Darcy approximation using the Lyapunov direct method. The effect of stress relaxation on the linear and non-linear critical stability parameters is clearly brought out with coincidence between the two when the solute concentration is dilute. Qualitatively, the result of porous and clear fluid cases is shown to be similar. In spite of lack of symmetry in the problem it is shown that non linear exponential stability can be handled.

Źródło:

International Journal of Applied Mechanics and Engineering; 2013, 18, 1; 125-135
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 84.

Tytuł:

CuO–water mhd mixed convection analysis and entropy generation minimization in double-lid–driven u-shaped enclosure with discrete heating

Autorzy:

Mliki, Bouchmel
Miri, Rached
Djebali, Ridha
Abbassi, Mohamed A.

Powiązania:

https://bibliotekanauki.pl/articles/2204647.pdf

Data publikacji:

2023

Wydawca:

Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej

Tematy:

U-shaped enclosure
MHD mixed convection
nanoliquids
double lid-driven cavity
entropy generation
LBM

Opis:

The present study explores magnetic nanoliquid mixed convection in a double lid–driven U-shaped enclosure with discrete heat-ing using the lattice Boltzmann method (LBM) numerical method. The nanoliquid thermal conductivity and viscosity are calculated using the Maxwell and Brinkman models respectively. Nanoliquid magnetohydrodynamics (MHD) and mixed convection are analyzed and entropy generation minimisation has been studied. The presented results for isotherms, stream isolines and entropy generation describe the interaction between the various physical phenomena inherent to the problem including the buoyancy, magnetic and shear forces. The operating parameters’ ranges are: Reynolds number (Re: 1–100), Hartman number (Ha: 0–80), magnetic field inclination (γ: 0°–90°), nanoparticles volume fraction (ϕ: 0–0.04) and inclination angle (α: 0°–90°). It was found that the and the total entropy generation augment by increasing Re, ϕ: and γ. conversely, an opposite effect was obtained by increasing Ha and α. The optimum magnetic field and cavity inclination angles to maximum heat transfer are γ = 90° and α = 0.

Źródło:

Acta Mechanica et Automatica; 2023, 17, 1; 112--123
1898-4088
2300-5319

Pojawia się w:

Acta Mechanica et Automatica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 85.

Tytuł:

New analysis of natural convection boundary layer flow on a horizontal plate with variable wall temperature
Nowa analiza naturalnego opływu konwekcyjnej warstwy przyściennej na poziomej płycie o zróżnicowanej temperaturze powierzchni

Autorzy:

Mehrizi, A. A.
Vazifeshenas, Y.
Domairry, G.

Powiązania:

https://bibliotekanauki.pl/articles/281672.pdf

Data publikacji:

2012

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

free convection
HAM (Homotopy Analysis Method)
analytical solution

Opis:

In this study, steady laminar free convection boundary layer flow on a horizontal plate is investigated through analytical solutions. By transforming the governing non-dimensional boundary layer equations into an ordinary differential equation, the application of the Homotopy Analysis Method can be practical. So in this case, the analytical results for different Prandtl numbers and constant M values which portray the power index are achieved. The trend goes on large amounts of (M ��>> 1) and the results are compared with other efforts. Furthermore, the effects of different values of Prandtl number and M values on temperature and velocity profiles are verified.
W pracy zajęto się swobodnym, laminarnym opływem konwekcyjnej warstwy przyściennej na poziomej płycie w ujęciu czysto analitycznym. Bezwymiarowe równania warstwy przekształcono do postaci różniczkowej zwyczajnej, co pozwoliło na zastosowanie metody homotopii. Otrzymano analityczne wyniki określające wykładnik potęgowy opływu dla różnych wartości liczby Prandtla oraz stałej M. Badania rozszerzono na �>> 1, a rezultaty porównano z opracowaniami innych badaczy. Zweryfikowano również wpływ liczby Prandtla oraz stałej M na rozkład temperatury i prędkości opływu w rozważanej warstwie.

Źródło:

Journal of Theoretical and Applied Mechanics; 2012, 50, 4; 1001-1010
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 86.

Tytuł:

Model neuronowy zmian temperatury podczas konwekcyjnego suszenia zrębków wierzby energetycznej
Neural model of temperature changes during convection drying of energy willow chips

Autorzy:

Łapczyńska-Kordon, B.
Francik, S.
Ślipek, Z.

Powiązania:

https://bibliotekanauki.pl/articles/289751.pdf

Data publikacji:

2008

Wydawca:

Polskie Towarzystwo Inżynierii Rolniczej

Tematy:

wierzba
zrębki
model neuronowy
zmiana temperatury
suszenie konwekcyjne
willow chips
neural model
temperature change
convection drying

Opis:

W pracy podjęto próbę zastosowania sztucznych sieci neuronowych do modelowania rozkładu temperatury w zrębkach suszonych konwekcyjnie. W modelu uwzględniono cztery zmienne wejściowe: temperaturę czynnika suszącego, początkową zawartość wody, wymiary zrębka, czas suszenia oraz jedna wyjściową - temperaturę materiału. Do budowy modelu posłużyły wyniki badań procesu konwekcyjnego suszenia zrębków wierzby, w trzech temperaturach: 50, 60 i 70°C, w suszarce z wymuszonym obiegiem powietrza. Podczas suszenia, w równych odstępach czasowych, określano zawartość wody i temperaturę materiału. Sformułowany model w oparciu o sztuczne sieci neuronowe został wybrany na podstawie najmniejszej wartości błędu średnio kwadratowego dla zbioru walidacyjnego. Następnie model ten poddano testowaniu i weryfikacji za pomocą wyników pomiarów wykonanych w takich samych warunkach jak opisane powyżej. Stwierdzono, że model poprawnie opisuje kinetykę zmian temperatury materiału w zależności od wybranych czterech czynników wejściowych.
The paper demonstrates an attempt to employ artificial neural networks to model temperature distribution in chips being dried in the convection process. Four input variables were taken into account in the model: drying medium temperature, initial water content, chip dimensions and drying time, and one output variable - material temperature. Examination results for willow chips convection drying process, carried out at three temperature values: 50, 60 and 70°C in a drier with forced air flow were used to build the model. During drying the researchers were determining water content and material temperature at equal time intervals. The model formulated using artificial neural networks was selected according to the lowest mean square error value for validation set. Then, this model was subject to testing and verification using results of measurements performed in the same conditions as those described above. It has been observed that the model correctly describes kinetics of changes in material temperature depending on the selected four input factors.

Źródło:

Inżynieria Rolnicza; 2008, R. 12, nr 11(109), 11(109); 149-155
1429-7264

Pojawia się w:

Inżynieria Rolnicza

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 87.

Tytuł:

Model neuronowy zmian zawartości wody w zrębkach wierzby podczas konwekcyjnego suszenia
Neural model of changes in water content in willow chips during convection drying

Autorzy:

Łapczyńska-Kordon, B.
Francik, S.

Powiązania:

https://bibliotekanauki.pl/articles/289777.pdf

Data publikacji:

2008

Wydawca:

Polskie Towarzystwo Inżynierii Rolniczej

Tematy:

zrębki
wierzba
model neuronowy
zawartość wody
suszenie konwekcyjne
willow chips
neural model
water content
convection drying

Opis:

Celem pracy było opracowanie modelu zmian zawartości wody w zrębkach wierzby energetycznej w czasie, w postaci sztucznej sieci neuronowej. Model został opracowany w oparciu o wyniki badań procesu konwekcyjnego suszenia zrębków wierzby o długości 2 cm, ale różnej średnicy, w suszarce laboratoryjnej z wymuszonym przepływem powietrza. Materiał był suszony w temperaturach 40, 50, 60 i 70°C. Na podstawie otrzymanych wyników badań został sformułowany, za pomocą SSN, model zmian zawartości wody w zależności od sześciu zmiennych wejściowych: czasu suszenia, temperatury czynnika suszącego, długości i średnicy zrębków oraz początkowej zawartości wody i masy zrębków. Spośród opracowanych modeli wybrano model o architekturze MLP 6:6-15-14-1:1, ponieważ podczas weryfikacji empirycznej stwierdzono, że obliczony błąd średniokwadratowy dla tego modelu był najmniejszy.
The purpose of the work was to develop a model of changes in time of water content in energy willow chips using artificial neural networks (ANN). The model was developed on the grounds of examination results obtained for convection process applied for drying of 20mm-long willow chips with different diameters, carried out in a laboratory drier with forced air flow. The material was dried at the temperature of 40, 50, 60 and 70°C. Obtained examination results provided grounds to formulate, using the ANN, the model of changes in water content depending on six input variables: drying time, drying medium temperature, length and diameter of chips, and initial water content and weight of chips. The model with MLP architecture 6:6-15-14-1:1 was chosen from among all developed models because empirical verification proved that computed mean square error for that model was lowest.

Źródło:

Inżynieria Rolnicza; 2008, R. 12, nr 11(109), 11(109); 143-148
1429-7264

Pojawia się w:

Inżynieria Rolnicza

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 88.

Tytuł:

Radiation and chemical reaction effects on unsteady MHD free convection parabolic flow past an infinite isothermal vertical plate with viscous dissipation

Autorzy:

Reddy, B. Prabhakar

Powiązania:

https://bibliotekanauki.pl/articles/265160.pdf

Data publikacji:

2019

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

promieniowanie
reakcja chemiczna
magnetohydrodynamika
swobodna konwekcja
płyta pionowa
radiation parameter
chemical reaction parameter
porous medium
MHD
free convection
isothermal vertical plate

Opis:

The numerical investigation of the effects of radiation and chemical reaction on an unsteady MHD free convection flow with a parabolic starting motion of an infinite isothermal vertical porous plate taking into account the viscous dissipation effect has been carried out. The fluid is considered a gray, absorbing emitting radiation but a non-scattering medium. The dimensionless governing equations for this investigation are solved numerically by applying the Ritz finite element method. Numerical results for the velocity profiles, temperature profiles and concentration profiles as well as the skin-friction are presented through graphs and tables for different values of the physical parameters involved. Results obtained show a decrease in the temperature and velocity in the boundary layer as the radiation parameter increased. The velocity increases with an increase in the thermal and mass Grashof numbers and decreases with an increase in the magnetic parameter. Further, the concentration and velocity decreases with increasing the Schmidt number and chemical reaction parameter. These findings are in very good agreement with the studies reported earlier.

Źródło:

International Journal of Applied Mechanics and Engineering; 2019, 24, 2; 343-358
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 89.

Tytuł:

The effect of thermal modulation on double diffusive convection in the presence of applied magnetic field and internal heat source

Autorzy:

Manjula, S. H.
Suresh, P.
Rao, M. G.

Powiązania:

https://bibliotekanauki.pl/articles/1839901.pdf

Data publikacji:

2021

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

analiza nieliniowa
płyn newtonowski
konwekcja
thermal modulation
weak nonlinear analysis
internal heating
newtonian fluid
double diffusive convection

Opis:

The investigation of thermal modulation on double-diffusive stationary convection in the presence of an applied magnetic field and internal heating is carried out. A weakly nonlinear stability analysis has been performed using the finite-amplitude Ginzburg-Landau model. This finite amplitude of convection is obtained at the third order of the system. The study considers three different forms of temperature modulations. OPM-out of phase modulation, LBMO-lower boundary modulation, IPM-in phase modulation. The finite-amplitude is a function of amplitude ,Tδ frequency ω and the phase differenceθ . The effects of Tδ and ω on heat/mass transports have been analyzed and depicted graphically. The study shows that heat/mass transports can be controlled effectively by thermal modulation. Further, it is found that the internal Rayleigh number iR enhances heat transfer and reduces the mass transfer in the system.

Źródło:

International Journal of Applied Mechanics and Engineering; 2021, 26, 1; 135-155
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 90.

Tytuł:

Matematyczne modelowanie termicznej degradacji kwasu L-askorbinowego w czasie konwekcyjnego suszenia pora
Mathematical modelling of thermal degradation of L-ascorbic acid during convection drying of leek

Autorzy:

Rudy, S.

Powiązania:

https://bibliotekanauki.pl/articles/290545.pdf

Data publikacji:

2006

Wydawca:

Polskie Towarzystwo Inżynierii Rolniczej

Tematy:

kwas L-askorbinowy
modelowanie matematyczne
por
suszenie konwekcyjne
L-ascorbic acid
mathematical modelling
leek
convection drying

Opis:

W pracy wyznaczono zmiany zawartości kwasu L-askorbinowego w funkcji czasu trwania procesu konwekcyjnego suszenia na czterech poziomach temperatury i dla dwóch prędkości przepływu powietrza suszącego. Na podstawie uzyskanych danych eksperymentalnych opracowano model matematyczny tych zmian w oparciu o równanie Bigielowa. Opracowany model matematyczny zmian zawartości kwasu L- askorbinowego w funkcji czasu konwekcyjnego suszenia pora (v=0,3 i 0,5 m/s) został zweryfikowany, gdyż błędy modelu, praktycznie w całym zakresie pomiarowym przekraczają 4%.
In the study, the changes L-ascorbic acid content in function of the duration of the convection drying process at four temperature levels and for two drying air flow speed values were determined. Based on the experimental data, a mathematical model of those changes was developed, based on Bigelow equation. The mathematical model of L-ascorbic acid content changes in function of duration of convection drying of leek (v=0.3 and 0.5 m/s) was verified, because the error of the model exceed 4% virtually in all the measurement range.

Źródło:

Inżynieria Rolnicza; 2006, R. 10, nr 6(81), 6(81); 203-212
1429-7264

Pojawia się w:

Inżynieria Rolnicza

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 91.

Tytuł:

Unsteady laminar mixed convection boundary layer flow near a vertical wedge due to oscillations in the free-stream and surface temperature

Autorzy:

Roy, N. C.
Hossain, A.
Hussain, S.

Powiązania:

https://bibliotekanauki.pl/articles/264762.pdf

Data publikacji:

2016

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja mieszana
granica przepływu warstwy
przepływ ciepła
mixed convection
boundary layer flow
vertical wedge
free-stream oscillation

Opis:

The unsteady laminar boundary layer characteristics of mixed convection flow past a vertical wedge have been investigated numerically. The free-stream velocity and surface temperature are assumed to be oscillating in the magnitude but not in the direction of the oncoming flow velocity. The governing equations have been solved by two distinct methods, namely, the straightforward finite difference method for the entire frequency range, and the extended series solution for low frequency range and the asymptotic series expansion method for high frequency range. The results demonstrate the effects of the Richardson number, Ri, introduced to quantify the influence of mixed convection and the Prandtl number, Pr, on the amplitudes and phase angles of the skin friction and heat transfer. In addition, the effects of these parameters are examined in terms of the transient skin friction and heat transfer.

Źródło:

International Journal of Applied Mechanics and Engineering; 2016, 21, 1; 169-186
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 92.

Tytuł:

MHD mixed convection in copper-water nanofluid filled lid-driven square cavity containing multiple adiabatic obstacles with discrete heating

Autorzy:

Gorla, R. S. R.
Siddiqa, S.
Hasan, A. A.
Salah, T.
Rashad, A. M.

Powiązania:

https://bibliotekanauki.pl/articles/265383.pdf

Data publikacji:

2020

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

nanociecze
konwekcja mieszana
magnetohydrodynamika
nanofluid
mixed convection
magnetohydrodynamics
square cavity
adiabatic obstacles

Opis:

The objective of the present work is to investigate the influence of nanoparticles of copper within the base fluid (water) on magneto-hydrodynamic mixed-convection flow in a square cavity with internal generation. A control finite volume method and SIMPLER algorithm are used in the numerical calculations. The geometry is a lid-driven square cavity with four interior square adiabatic obstacles. A uniform heat source is located in a part of the left wall and a part of the right wall of the enclosure is maintained at cooler temperature while the remaining parts of the two walls are thermally insulated. Both the upper and bottom walls of the cavity are considered to be adiabatic. A comparison with previously published works shows a very good agreement. It is observed that the Richardson number, Ri, significantly alters the behavior of streamlines when increased from 0.1 to 100.0. Also, the heat source position parameter, D, significantly changes the pattern of isotherms and its strength shifted when D moves from 0.3 to 0.7.

Źródło:

International Journal of Applied Mechanics and Engineering; 2020, 25, 2; 57-74
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 93.

Tytuł:

Heat transfer processes in installations with photovoltaic roof tiles

Autorzy:

Kurz, D.

Powiązania:

https://bibliotekanauki.pl/articles/97640.pdf

Data publikacji:

2016

Wydawca:

Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej

Tematy:

photovoltaic roof tile
convection
radiation
conduction
heat transfer

Opis:

The paper presents the classification of methods of heat transfer, and the procedure when determining criterion equations depending on the type of heat exchange. It describes the heat transfer coefficients and resistance of heat transfer by convection. It also indicates the workflow to determine the quantitative heat flow in the present system of photovoltaic roof tiles installed in the roof structure.

Źródło:

Computer Applications in Electrical Engineering; 2016, 14; 444-456
1508-4248

Pojawia się w:

Computer Applications in Electrical Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 94.

Tytuł:

Analysis of thermal stratified storage tank

Autorzy:

Smusz, R.
Kielan, P.
Mazur, D.

Powiązania:

https://bibliotekanauki.pl/articles/140948.pdf

Data publikacji:

2017

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

temperature stratification
thermal energy
heat recovery
convection

Opis:

The basic aim of the task is to compile a temperature stratification system in an accumulation tank. The range of the thesis concerns the shape and dimensions of a stratification system for an accumulation tank. Thermal stratification is a process that comprises the maintaining of temperature stratification at different levels of an accumulation tank which reduce to a minimum the process of temperature equalization. It results from the fact that the thermal stratification in a tank significantly increases the installation efficiency and improves the process of energy storing. It is connected with a thermodynamic element quality, that is the higher the temperature, the higher the energy, and, thus, the thermosdynamic element quality. In this phenomenon, thanks to the same amount of accumulated thermal energy and average temperature, as in a fully mixed tank, the user has a higher temperature in the upper part of the tank at his disposal. It has significant importance in the case when there is a low-temperature heating medium that transfers heat to the accumulation tank. Such a situation occurs when heat is absorbed from synthetic freons used in cooling and air-conditioning systems.

Źródło:

Archives of Electrical Engineering; 2017, 66, 3; 631-642
1427-4221
2300-2506

Pojawia się w:

Archives of Electrical Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 95.

Tytuł:

Symulacja konwekcji wymuszonej w przewodach prostoosiowych przy przepływie laminarnym metodą elementów brzegowych
Boundary elements method simulation of laminar flow forced convection in duct

Autorzy:

Teleszewski, T.

Powiązania:

https://bibliotekanauki.pl/articles/371849.pdf

Data publikacji:

2014

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

konwekcja wymuszona
przewody prostoosiowe
liczba Nusselta
metoda elementów brzegowych (MEB)
forced convection
flow in ducts
Nusselt number
boundary element method (BEM)

Opis:

W pracy przedstawiono algorytm symulacji konwekcji wymuszonej MEB przy przepływie laminarnym w przewodach prostoosiowych niezależnie od kształtu poprzecznego przewodu. Weryfikacja algorytmu została wykonana poprzez porównanie rezultatów MEB z rozwiązaniem analitycznym. W publikacji wyznaczono zależność liczby Nusselta od liczby boków w przewodach o przekroju wielokąta foremnego.
The paper presents the numerical algorithm Boundary Element Method to simulation modelling forced convection in a duct. The efficiency and the credibility of proposed algorithm were verified by numerical tests in theoretical solution. A numerical examples are presented fully developed forced convection through pentagon duct. In this study is proposed for determining the Nusselt number in regular polygonal channels.

Źródło:

Zeszyty Naukowe. Inżynieria Środowiska / Uniwersytet Zielonogórski; 2014, 153 (33); 117-127
1895-7323

Pojawia się w:

Zeszyty Naukowe. Inżynieria Środowiska / Uniwersytet Zielonogórski

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 96.

Tytuł:

Modelowanie numeryczne opływu budynków. Wpływ zjawiska konwekcji na pole przepływu
Numerical investigations on the flow field generation in building surroundings. An influence of convection of the flow field

Autorzy:

Świderski, K.

Powiązania:

https://bibliotekanauki.pl/articles/213805.pdf

Data publikacji:

2008

Wydawca:

Sieć Badawcza Łukasiewicz - Instytut Lotnictwa

Tematy:

modelowanie numeryczne opływu budynków
zjawisko konwekcji
przepływ
numerical investigations on the flow
convection on the flow field

Opis:

W artykule przedstawiono metodykę określenia pola przepływu w otoczeniu budynków z wykorzystaniem komercyjnego pakietu Ansys FluentŽ. Rozpatrywane były różne przypadki obliczeniowe, na które skladają się orientacja budynku lub budynków względem kierunku wiatru oraz prędkość wiatru. Przedstawiono również wyniki modelowania opływu budynku z uwzględnieniem konwekcji (przypadek pożaru).
In this paper the metodology of describing the flow field in a near of buildings is presented. In order to perform computational simulations a commercial software Ansys FluentŽ has been used. Expecially, the results of simulations of the flow field with convection and radiation taken into account (in case of fire) are presented.

Źródło:

Prace Instytutu Lotnictwa; 2008, 3-4 (194-195); 166-170
0509-6669
2300-5408

Pojawia się w:

Prace Instytutu Lotnictwa

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 97.

Tytuł:

Wpływ warunków konwekcyjnego i sublimacyjnego suszenia korzeni marchwi na jakość suszu
Effect of convection and freeze drying conditions on the quality of dried carrot roots

Autorzy:

Gawełek, J.

Powiązania:

https://bibliotekanauki.pl/articles/292243.pdf

Data publikacji:

2005

Wydawca:

Polskie Towarzystwo Inżynierii Rolniczej

Tematy:

marchew
suszenie konwekcyjne
suszenie sublimacyjne
liofilizacja
jakość suszu
carrot roots
convection drying
freeze drying
lyophilization
quality of dried product

Opis:

W pracy określono wpływ temperatury czynnika suszącego (w przypadku suszenia konwekcyjnego), oraz temperatury płyty grzejnej (w przypadku suszenia sublimacyjnego) na jakość suszu marchwi. Materiał badawczy stanowiły kostki marchwi o wymiarze boku równym 10 mm, odmiany NEWTON. Badanymi wyróżnikami jakości otrzymywanego suszu były: analiza sensoryczna suszu przed rehydratacją, analiza sensoryczna suszu po rehydratacji, zdolność pochłaniania wody przez susz, zawartość β-karotenu. Z oceny sensorycznej suszu wynika, że ze wzrostem temperatury suszenia (w obu sposobach suszenia) jakość suszu marchwi ulega pogorszeniu, przy czym w przypadku suszenia sublimacyjnego w zdecydowanie mniejszym stopniu niż w przypadku suszenia konwekcyjnego. Zdolność pochłaniania wody przez susz maleje ze wzrostem temperatury suszenia zarówno w przypadku suszenia konwekcyjnego jak i sublimacyjnego; charakter zmian w obu przypadkach jest analogiczny. Ubytki β-karotenu w procesie suszenia wzrastają ze wzrostem temperatury suszenia w przypadku obu technik suszenia, przy czym w przypadku liofilizacji (suszenia sublimacyjnego) wzrost jest nieznaczny, natomiast w przypadku suszenia konwekcyjnego dla temperatur powyżej 70ºC obserwuje się zdecydowanie większe ubytki β-karotenu. Wszystkie badane wyróżniki jakości suszu marchwi wskazują na zdecydowanie lepszą jakość produktu liofilizowanego niż produktu suszonego konwekcyjnie w całym badanym zakresie temperatur (w większości przypadków wyróżniki jakościowe liofilizatu przewyższały 2-krotnie analogiczne wyróżniki suszu konwekcyjnego).
Paper discussed the influence of drying agent temperature (in the case of convection drying) and the temperature of heating plate (in the case of freeze drying) on the quality of dried carrot roots. The roots of carrot, Newton cultivar, cut into cubes of 10 mm side, were used as the material for studies. The quality factors of obtained dried products were: sensory analysis before and after dehydration, the ability of water absorption and β-carotene content. Sensory evaluation showed that at time increase of drying temperature (at both drying techniques) the quality of dried product worsened, however in the case of freeze drying to much less extent than at convection drying. The ability of water absorption by dried product decrease along with increasing of drying temperature, both at convection and freeze drying; the character of changes was analogical at both drying techniques. The loss of β-carotene during drying rose with increasing drying temperature for both techniques of drying; the losses increased slightly at freeze drying (lyophilization), whereas in case of convection drying at the temperature above 70 deg C much higher β-carotene losses were observed. All tested quality factors of dried carrot roots showed much better quality of the lyophilized product than the product dried by convection for the whole range of tested temperatures (in most cases the quality factors of lyophilized material were twice higher than analogical factors of convection dried product).

Źródło:

Inżynieria Rolnicza; 2005, R. 9, nr 11, 11; 119-127
1429-7264

Pojawia się w:

Inżynieria Rolnicza

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 98.

Tytuł:

Effects of Hall current on unsteady hydromagnetic free convection flow past an impulsively moving vertical plate with Newtonian heating

Autorzy:

Seth, G. S.
Sarkar, S.
Sharma, R.

Powiązania:

https://bibliotekanauki.pl/articles/264598.pdf

Data publikacji:

2016

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

przepływ konwekcyjny
transformacja Laplace'a
tarcie
hydromagnetic free convection flow
Newtonian heating
Hall current
porous medium
INVLAP routine in Matlab

Opis:

An investigation of unsteady hydromagnetic free convection flow of a viscous, incompressible and electrically conducting fluid past an impulsively moving vertical plate with Newtonian surface heating embedded in a porous medium taking into account the effects of Hall current is carried out. The governing partial differential equations are first subjected to the Laplace transformation and then inverted numerically using INVLAP routine of Matlab. The governing partial differential equations are also solved numerically by the Crank-Nicolson implicit finite difference scheme and a comparison has been provided between the two solutions. The numerical solutions for velocity and temperature are plotted graphically whereas the numerical results of skin friction and the Nusselt number are presented in tabular form for various parameters of interest. The present solution in special case is compared with a previously obtained solution and is found to be in excellent agreement.

Źródło:

International Journal of Applied Mechanics and Engineering; 2016, 21, 1; 187-203
1734-4492
2353-9003

Pojawia się w:

International Journal of Applied Mechanics and Engineering

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 99.

Tytuł:

Konwekcja naturalna w modelowym pomieszczeniu z zastosowaniem aproksymacji Bussinesq’a
Natural convection in a model chamber with the Boussinesq approximation utilization

Autorzy:

Radzikowska-Juś, W.
Owczarek, S.

Powiązania:

https://bibliotekanauki.pl/articles/209933.pdf

Data publikacji:

2017

Wydawca:

Wojskowa Akademia Techniczna im. Jarosława Dąbrowskiego

Tematy:

rozkład temperatury w modelowym pomieszczeniu
konwekcja Rayleigha-Benarda
aproksymacja Bussinesqa
temperature distribution in the model room
Rayleigh-Benard convection
Bussinesq approximation

Opis:

Artykuł przedstawia analizę numeryczną przepływu ciepła w czasie w modelowym pomieszczeniu w wyniku umieszczenia w nim obiektu o podwyższonej temperaturze. W wyniku różnicy temperatur pomiędzy obiektem a otoczeniem w pomieszczeniu następuje zjawisko konwekcji naturalnej. Obliczenia wykonywano z wykorzystaniem oprogramowania ELMER bazującego na metodzie elementów skończonych. W celu zmniejszenia ich złożoności w symulacji wykorzystano aproksymację Bussinesqa. Rozpatrywany przypadek jest zbliżony do konwekcji Rayleigha-Benarda, która stanowi punkt wyjścia dla przeprowadzonej analizy.
The paper presents numerical analysis of heat transfer inside a model chamber in time after entering an object of elevated temperature therein. As a result of the temperature difference between the object and the environment in the room, natural convection has occurred. Numerical simulations were performed using ELMER software based on the Finite Element Method. In order to reduce the complexity of the simulation, the Bussinesq approximation was used. The relevant case is similar to Rayleigh-Benard convection, which was starting point to the conducted analysis.

Źródło:

Biuletyn Wojskowej Akademii Technicznej; 2017, 66, 3; 75-82
1234-5865

Pojawia się w:

Biuletyn Wojskowej Akademii Technicznej

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 100.

Tytuł:

Triple-diffusive convection in Walters' (Model B') fluid with varying gravity field saturating a porous medium

Autorzy:

Kango, S. K.
Rana, G. C.
Chand, R.

Powiązania:

https://bibliotekanauki.pl/articles/178886.pdf

Data publikacji:

2013

Wydawca:

Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej

Tematy:

lepkosprężyste ciecze Walters B
ciecz Waltersa
ośrodek porowaty
konwekcja
Walters' (model B') fluid
Walters' B liquid model
Walters' B' fluid
porous media
convection

Opis:

The Triple-Diffusive convection in Walters’ (Model B') fluid with varying gravity field is considered in the presence of uniform vertical magnetic field in porous medium. For the case of stationary convection, the magnetic field, varying gravity field and the stable solute gradients have stabilizing effects whereas the medium permeability has destabilizing (or stabilizing) effect on the system under certain conditions. A linear stability analysis theory and normal mode analysis method have been carried out to study the onset convection. The kinematic viscoelasticity has no effect on the stationary convection. The solute gradients, magnetic field, varying gravity field, porosity and kinematic viscoelasticity introduce oscillatory modes in the system, which were non-existent in their absence. The sufficient conditions for the non-existence of overstability are also obtained. The results are also shown graphically.

Źródło:

Studia Geotechnica et Mechanica; 2013, 35, 3; 45-56
0137-6365
2083-831X

Pojawia się w:

Studia Geotechnica et Mechanica

Dostawca treści:

Biblioteka Nauki

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