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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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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/Pl (1 + 2π2F + PlQ/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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
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
Artykuł
Wyświetlanie 1-50 z 298

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