Skocz do pozycji: 1.

Tytuł:

Definition of dimensionless coefficient of resistance and coefficient of roughness in cross-section of stream with large roughness element

Autorzy:

Michalec, B.
Strutynski, M.

Powiązania:

https://bibliotekanauki.pl/articles/59718.pdf

Data publikacji:

2010

Wydawca:

Polska Akademia Nauk. Stowarzyszenie Infrastruktura i Ekologia Terenów Wiejskich PAN

Tematy:

Rudawa River
Bedkowka Stream
stream
large roughness grain
dimensionless coefficient
roughness coefficient
hydraulic condition
water flow
flow channel bottom
flow channel distribution

Opis:

The results of investigations carried out in the stream Będkówka – a left bank tributary of the Rudawa River are presented in this paper. A stream sector with large roughness element was chosen for investigations. The performed measurements included cross-section leveling and longitudinal leveling of the stream channel, bed load (sediment) sampling, and hydrometric measurements. Cross section leveling included five cross-sections in the 19-m long stream sector; these were located upstream and downstream the large roughness element and in its region. Differentiation of flow velocity in the region of large roughness element and its influence on differentiation of the load granulometric composition in the stream channel was shown. Immediately downstream the large roughness grain zone a fine grain sediment was frapped, its diameter d50 was seven to ten times smaller than that of the sediment in bed present in the stream channel. The dimensionless coefficient of resistance was calculated taking into account the equivalent bottom roughness determined in each of the examined sections by use of Gladki`s formulae. It was found that the large roughness element in the Będkówka stream caused a change of hydraulic conditions of water flow and, in consequence, the dimensionless coefficient of resistance in the grain section increased by about four times. The coefficient of channel roughness was also determined and it was shown that the coefficient of roughness in the section of large roughness element determined with consideration of the determined dimensionless coefficient of resistance increased on the average in the section of large roughness grain by over 34% in relation to the coefficient of channel roughness.

Źródło:

Infrastruktura i Ekologia Terenów Wiejskich; 2010, 11
1732-5587

Pojawia się w:

Infrastruktura i Ekologia Terenów Wiejskich

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 2.

Tytuł:

Organizacja badań diagnostycznych okrętowego tłokowego silnika spalinowego o ograniczonej podatności kontrolnej
Organization of diagnostic investigations of marine engine of limited monitoring susceptability

Autorzy:

Korczewski, Z.
Zacharewicz, M.

Powiązania:

https://bibliotekanauki.pl/articles/222576.pdf

Data publikacji:

2009

Wydawca:

Akademia Marynarki Wojennej. Wydział Dowodzenia i Operacji Morskich

Tematy:

diagnostyka
silniki okrętowe
doładowanie
kanały przepływowe
diagnostics
marine engines
supercharging
flow channel

Opis:

W artykule przedstawiono założenia wstępne opracowywanej w Akademii Marynarki Wojennej metody diagnozowania przestrzeni roboczych okrętowych tłokowych silników spalinowych o ograniczonej podatności kontrolnej niewyposażonych standardowo w zawory indykatorowe. Sformułowano problem badawczy oraz główne cele prowadzonych badań. Zdefiniowano pojęcie przestrzeni roboczych silnika oraz dokonano analizy czynników mających wpływ na degradację ich struktury konstrukcyjnej. Przeprowadzono dyskusję nad stosowanymi obecnie strategiami eksploatacji silników okrętowych, tzn. eksploatacją według resursu godzinowego, stanu technicznego oraz poziomu niezawodności. Scharakteryzowano zależności istniejące pomiędzy poszczególnymi stanami obiektu diagnozowania - przestrzeniami roboczymi silnika okrętowego. Prowadzone w artykule rozważania przedstawione zostały na tle osiągnięć zagranicznych i krajowych ośrodków naukowo-badawczych zajmujących się podejmowanym projektem badawczym. Pozwoliło to na doprecyzowanie schematu realizacji badań procesów gazodynamicznych dla celów diagnostyki okrętowego tłokowego silnika spalinowego.
The paper presents preliminary assumptions of the new diagnostic method concerning the marine diesel engine's workspace areas, which was developed at the Polish Naval Academy. It is expected that the method will be very useful to diagnose technical condition of marine diesel engines at limited monitoring susceptibility, i.e. the ones which are not equipped with indicator valves. It includes the research problem and main purposes of the research. The paper defines the notion of the workspace areas and does an analysis of factors that have the highest impact on destruction phenomenon. The paper also considers strategies used at present to run marine diesel engines: according to the engine installation life, according to the technical shape as well as according to the level of reliability. It characterises mutual interdependences between characteristic technical conditions of the research object (workspace areas). The research conducted is shown at the background of achievements of foreign and national scientific centres. This way the research diagram of gas-dynamical processes was made more precise for diagnostic purposes of marine diesel engines.

Źródło:

Zeszyty Naukowe Akademii Marynarki Wojennej; 2009, R. 50 nr 2 (177), 2 (177); 41-56
0860-889X

Pojawia się w:

Zeszyty Naukowe Akademii Marynarki Wojennej

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 3.

Tytuł:

Preliminary calculations of flow in channel with triangular and rectangular obstacle

Autorzy:

Kmiotek, M.
Kucaba-Pietal, A.

Powiązania:

https://bibliotekanauki.pl/articles/1955312.pdf

Data publikacji:

2010

Wydawca:

Politechnika Gdańska

Tematy:

fluid flow
flow in a channel
CFD

Opis:

The paper presents the results of preliminary numerical calculations of a fluid flow in a channel with an obstacle. The flow problem was solved with an application of the finite elements method. Various geometries of obstacles were considered.

Źródło:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2010, 14, 4; 329-337
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: 4.

Tytuł:

Numerical analysis of open channel steady gradually varied flow using the simplified Saint-Venant equations

Autorzy:

Artichowicz, W.

Powiązania:

https://bibliotekanauki.pl/articles/1934022.pdf

Data publikacji:

2011

Wydawca:

Politechnika Gdańska

Tematy:

dynamic equation
open-channel flow
open-channel networks
steady flow

Opis:

For one-dimensional open-channel flow modeling, the energy equation is usually used. There exist numerous approaches using the energy equation for open-channel flow computations, which resulted in the development of several very efficient methods for solving this problem applied to channel networks. However, the dynamic equation can be used for this purpose as well. This paper introduces a method for solving a system of non-linear equations by the discretization of the one-dimensional dynamic equation for open-channel networks. The results of the computations using the dynamic and energy equations were compared for an arbitrarily chosen problem. Also, the reasons for the differences between the solution of the dynamic and energy equation were investigated.

Źródło:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2011, 15, 3-4; 317-328
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: 5.

Tytuł:

Efficient implementation of a compact-pseudospectral method for turbulence modeling

Autorzy:

Tyliszczak, A.

Powiązania:

https://bibliotekanauki.pl/articles/1955215.pdf

Data publikacji:

2006

Wydawca:

Politechnika Gdańska

Tematy:

large eddy simulation
compact scheme
channel flow

Opis:

The paper is devoted to parallel implementation of a compact discretization scheme com-bined with the Fourier pseudospectral method. The idle time of processors resulting from the method of computating derivatives using compact schemes is eliminated by proper ordering of subtasks and by performing useful computations when processors are waiting for data from their neighbors. The correctnes of the algorithm is confirmed by comparison of results of LES simulations with DNS data for flow in a 3D channel with periodic non-slip wall boundary conditions.

Źródło:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2006, 10, 2; 125-138
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: 6.

Tytuł:

Experimental Analysis of Relations Between Coherent Turbulent Structures and Formation of Bedforms

Autorzy:

Termini, D.
Sammartano, V.

Powiązania:

https://bibliotekanauki.pl/articles/241077.pdf

Data publikacji:

2008

Wydawca:

Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN

Tematy:

open channel flow
sediment transport
bed forms
flow turbulence structure

Opis:

The present paper describes an experimental investigation on the interactions between flow turbulence and sediment motion. During the experiments, detailed measurements of flow velocity components were carried out using an Acoustic Doppler Velocimeter (ADV). The occurrence of turbulent events (inward interaction, ejection, sweep and burst) was verified through conditioned quadrant analysis. The quantitative information on the spatial and temporal evolution of turbulent events was obtained through space-time correlations of the conditioned data. As the primary objective was to analyse how turbulent structures influence formation of bedforms, the spatial scale of turbulent event evolution has been compared with the wavelength of bed-forms (alternate bars) observed on the bed. The analysis has essentially highlighted that such spatial scale compares well with the wavelength of the bars.

Źródło:

Archives of Hydro-Engineering and Environmental Mechanics; 2008, 55, 3-4; 125-143
1231-3726

Pojawia się w:

Archives of Hydro-Engineering and Environmental Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 7.

Tytuł:

Modelling of near-wall turbulence with large-eddy velocity modes
Modelowanie turbulencji za pomocą wielkoskalowych modów prędkości

Autorzy:

Wacławczyk, M.
Pozorski, J.

Powiązania:

https://bibliotekanauki.pl/articles/279207.pdf

Data publikacji:

2007

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

proper orthogonal decomposition
coherent structures
turbulent channel flow

Opis:

In the paper, low-order modelling of the turbulent velocity field in the near-wall region is performed using the Proper Orthogonal Decomposition (POD) approach. First, an empirical eigenfunction basis is computed, basing on two-point velocity correlations. Next, the Galerkin projection of the Navier-Stokes equations on the truncated basis is performed. This results in a system of Ordinary Differential Equations (ODEs) for time-dependent coefficients. Evolution of the largest vortical structures in the near-wall zone is then obtained from the time dependent coefficients and eigenfunctions. The system applied in the present work consists of 20 ODEs, the reconstructed velocity field is two-dimensional in the pIane perpendicular to the main flow direction. Moreover, the filtering procedure associated with the POD method is discussed, the POD filter is derived and compared with LES filters.
Przedmiotem pracy jest modelowanie turbulentnego pola prędkości w obszarze przyściennym za pomocą niskowymiarowego systemu dynamicznego, opartego o dekompozycję w bazie funkcji własnych POD (ang. Proper Orthogonal Decomposition). Empiryczna baza funkcyjna POD została wyznaczona z rozwiązania zagadnienia własnego, w którym obecne są dwupunktowe korelacje prędkości. Następnie, w wyniku projekcji Galerkina równań pędu na podprzestrzeń rozpiętą na tej bazie funkcyjnej, otrzymano układ równań różniczkowych zwyczajnych na zależne od czasu wspołczynniki. Na podstawie funkcji własnych oraz z wyznaczonych współczynników rozkładu uzyskano ewolucję w czasie charakterystycznych struktur wirowych w obszarze przyściennym. System dynamiczny rozpatrywany w pracy składa się z 20 równań różniczkowych zwyczajnych. Zrekonstruowane pole prędkości jest dwuwymiarowe (w płaszczyźnie prostopadłej do głównego kierunku przepływu). Ponadto w pracy dyskutowana jest procedura filtrowania związana z metodą POD. Wyprowadzony filtr POD porównano z formułą używaną w metodzie symulacji dużych wirów.

Źródło:

Journal of Theoretical and Applied Mechanics; 2007, 45, 3; 705-724
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 8.

Tytuł:

Lagrangian Model for a Single Saltating Grain in the Near-Wall Region of an Open-Channel Flow

Autorzy:

Czernuszenko, W.

Powiązania:

https://bibliotekanauki.pl/articles/241181.pdf

Data publikacji:

2013

Wydawca:

Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN

Tematy:

Lagrangian model
open-channel flow
particle-particle interaction

Opis:

A mathematical model for the continuous saltation of a particle near the granular bed in an open-channel flow is developed in detail. The model is based on the Lagrangian equations governing particle motion, and it takes into account the following forces: drag, lift, gravitation, virtual mass and the force responsible for particle-particle interactions. A model of particle-particle collisions is developed and used to determine the mean impulsive force acting upon a particle flowing and rebounding from the channel bed. The model can simulate the continuous saltation trajectories of a single particle in the near-bed region of turbulent flows, in which particle motion is controlled by collisions. The model has been calibrated and verified with available published data in a rather wide range of grain sizes from 0.53 mm to 15 mm. All parameters, such as lift, drag, restitution, friction coefficients and roughness height, have been set on the basis of a reanalysis of these published data.

Źródło:

Archives of Hydro-Engineering and Environmental Mechanics; 2013, 60, 1-4; 31-50
1231-3726

Pojawia się w:

Archives of Hydro-Engineering and Environmental Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 9.

Tytuł:

Numerical simulation of open channel flow between bridge piers

Autorzy:

Szydłowski, M.

Powiązania:

https://bibliotekanauki.pl/articles/1934025.pdf

Data publikacji:

2011

Wydawca:

Politechnika Gdańska

Tematy:

numerical simulation
open channel flow
mathematical modeling
bridge piers

Opis:

Free-surface flow in the vicinity of bridge piers on a fixed channel bed is a classical problem of open-channel hydraulics. This problem is usually analyzed using one-dimensional hydraulic models for steady-flow problems. The aim of this paper is to present a two-dimensional numerical simulation of water flow around obstacles, such as cylinders, which can act as a simplified model of real piers. The depth-averaged Navier-Stokes equations describing unsteady free-surface flow are solved using an explicit scheme of the finite-volume method. The numerical solution prepared for the simulations of unsteady free-surface flows was used here to analyze the case of steady flow. A numerical simulation of flow in the channel with the obstruction was performed for two different inflow discharges determining, respectively, the subcritical and supercritical flow in the cross-section of a channel constriction. In the second simulation, a hydraulic jump was observed downstream of the bridge section. The numerical results were compared with measurements. Water surface profiles were measured for both discharges in the hydraulic laboratory of the Faculty of Civil and Environmental Engineering at Gdansk University of Technology (GUT). Comparisons with laboratory data showed that the proposed approach constitutes a sufficiently accurate and reliable technique for predicting basic flow parameters. The method of two-dimensional modeling of flow in a river channel between bridge piers can be also integrated with the simulation of unsteady flood wave propagation, ensuring a uniform approach to the problem of flood modeling in river valleys. Moreover, a two-dimensional simulation yields detailed information about flow structure near the obstruction, which can be used to better elucidate debris transport and river bed deformation processes.

Źródło:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2011, 15, 3-4; 271-282
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: 10.

Tytuł:

LES of converging-diverging channel flow with separation

Autorzy:

Kuban, L.
Elsner, W.
Tyliszczak, A.

Powiązania:

https://bibliotekanauki.pl/articles/1943209.pdf

Data publikacji:

2010

Wydawca:

Politechnika Gdańska

Tematy:

LES
turbulent boundary layer
separation
channel flow
pressure gradient

Opis:

The paper presents the results of LES simulation of two different turbulent channels with inlet conditions corresponding to the Reynolds number Re =395. In both cases a varying pressure gradient was obtained by an adequate curvature of one of the walls. The first case is treated as a benchmark and is used to validate the numerical procedure. This case is characterized by the same cross-section area at the inlet and outlet and a bump of a smooth profile located on one of the walls designed to be identical to the one used in the experiment conducted at Laboratorie de Mecanique de Lille (LML) (Marquillie et al., 2008). The second case corresponds to the geometry which reproduces the real geometry of the turbomachinery test section of the Czestochowa University of Technology. The test section was created in such a way as to produce the pressure gradient which would correspond to the conditions present in the axial compressor blade channel. The shape of both channels produced initially favorable (FPG) and then adverse pressure gradients (APG), and in this way created conditions for boundary layer separation. Due to a reverse flow where the turbulence transport is dictated by the dynamics of the large-scale eddies such a case is well suited to demonstrate predictive features of the LES technique.

Źródło:

TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2010, 14, 3; 283-295
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: 11.

Tytuł:

Numerical Modelling of Fish Passage with Turning Pools

Autorzy:

Maniecki, Ł.

Powiązania:

https://bibliotekanauki.pl/articles/241474.pdf

Data publikacji:

2018

Wydawca:

Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN

Tematy:

open channel flow
fishway
turbulence
numerical model
turning pool

Opis:

An assessment of operating conditions in a baffled fish passage with pool dimensions of 2:2 3:0 m, and 180 horizontally turning pools, was carried out using numerical computations and a site survey of water flow velocity distribution. Velocity was measured with a PMS electromagnetic flowmeter and a hydrometric current meter in representative cross-sections of the fish passage in the pool centres and in the baffle barrier cross-section area. Numerical computations were also performed for two alternative baffle locations in the fishway. One reflected the actual conditions, and the other was an alternative arrangement designed to improve hydraulic conditions for fish migration. The numerical model used the Large Eddy Simulation (LES) method, which makes it possible to detect large vortexes. The study pays close attention to the velocity field analysis as well as the distribution and sizes of vortexes in the turning pool of the culvert. The results of numerical computations and the site survey show high consistency, and the proposed baffle placement modification significantly improves flow conditions, especially in the entry section of the passage.

Źródło:

Archives of Hydro-Engineering and Environmental Mechanics; 2018, 65, 1; 41-66
1231-3726

Pojawia się w:

Archives of Hydro-Engineering and Environmental Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 12.

Tytuł:

On origin of unstable modes in viscous channel flow subject to periodically distributed surface suction
O pochodzeniu niestatecznych form zaburzeń w przepływie cieczy lepkiej w kanale z przestrzennie okresowym odsysaniem/wypływem

Autorzy:

Szumbarski, J.

Powiązania:

https://bibliotekanauki.pl/articles/281294.pdf

Data publikacji:

2002

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

periodic channel flow
linear stability
Floquet theory
surface suction

Opis:

The linear stability of a flow in a channel subject to periodically distributed suction applied at the wallsis investigated. The focus is on the relation between unstable modes observed in such a flow and the stability properties of the flow without suction (the Poiseuille flow). It is demonstrated that linearly unstable modes appearing in the presence of suction can be interpreted as modified Orr-Sommerfeld's or Squire's eigenmodes of the Poiseuille flow. Originally, these modes have the streamwise wave number equal to zero, i.e. they are invariant in the streamwise direction. When the surface suction is applied, the modes are additionally modulated along the channel and they become dependent on the streamwise variable. In the range of the parameters studied, a pair of such modes, one Orr-Sommerfeld's and one Squire's, can be simultaneously unstable. Certain properties of these modes are discussed in some details. Specifically, the influence of non-symmetric suction on stability characteristics is analysed.
W pracy rozważa się zagadnienie liniowej stateczności przepływu cieczy w płaskim kanale, w obecności periodycznie rozłożonego odsysania/wypływu przez ściany. Celem analizy jest identyfikacja zaburzeń krytycznych i objaśnienia ich związku z rozwiązaniami własnymi zagadnienia stateczności dla przepływu Poiseuille'a. Stosując metodę kontynuacji wartości i rozwiązań własnych po parametrze wykazano, że obserwowane formy niestabilności to zmodyfikowane okresowo w kierunku przepływu poprzeczne, symatryczne mody Squire'a i Orra-Sommerfelda, którym odpowiadają czysto urojone wartości własne. Zbadano numerycznie wpływ parametrów odsysania/wypływu na własności tych modów.

Źródło:

Journal of Theoretical and Applied Mechanics; 2002, 40, 4; 847-871
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 13.

Tytuł:

Lax-Wendroff and McCormack Schemes for Numerical Simulation of Unsteady Gradually and Rapidly Varied Open Channel Flow

Autorzy:

Machalińska-Murawska, J.
Szydłowski, M.

Powiązania:

https://bibliotekanauki.pl/articles/973864.pdf

Data publikacji:

2013

Wydawca:

Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN

Tematy:

open channel flow
mathematical modeling
numerical simulation
FDM schemes

Opis:

Two explicit schemes of the finite difference method are presented and analyzed in the paper. The applicability of the Lax-Wendroff and McCormack schemes for modeling unsteady rapidly and gradually varied open channel flow is investigated. For simulation of the transcritical flow the original and improved McCormack scheme is used. The schemes are used for numerical solution of one dimensional Saint-Venant equations describing free surface water flow. Two numerical simulations of flow with different hydraulic characteristics were performed – the first one for the extreme flow of the dam-break type and the second one for the simplified flood wave propagation problem. The computational results are compared to each other and to arbitrary solutions.

Źródło:

Archives of Hydro-Engineering and Environmental Mechanics; 2013, 60, 1-4; 51-62
1231-3726

Pojawia się w:

Archives of Hydro-Engineering and Environmental Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 14.

Tytuł:

Second law analysis of mhd forced convective nanoliquid flow through a two-dimensional channel

Autorzy:

Miri, Rached
Abbassi, Mohamed A.
Ferhi, Mokhtar
Djebali, Ridha

Powiązania:

https://bibliotekanauki.pl/articles/2204682.pdf

Data publikacji:

2022

Wydawca:

Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej

Tematy:

MHD
LBM
channel flow
nanoliquids
entropy generation
Brownian motion

Opis:

The present study deals with fluid flow, heat transfer and entropy generation in a two-dimensional channel filled with Cu–water nanoliquid and containing a hot block. The nanoliquid flow is driven along the channel by a constant velocity and a cold temperature at the inlet, and the partially heated horizontal walls. The aim of this work is to study the influence of the most important parameters such as nanoparticle volume fraction (0%≤ϕ≤4%), nanoparticle diameter (5 nm≤dp≤55 nm), Reynolds number (50≤Re≤200), Hartmann number (0≤Ha≤90), magnetic field inclination angle (0≤γ≤π) and Brownian motion on the hydrodynamic and thermal characteristics and entropy generation. We used the lattice Boltzmann method (LBM: SRT-BGK model) to solve the continuity, momentum and energy equations. The obtained results show that the maximum value of the average Nusselt number is found for case (3) when the hot block is placed between the two hot walls. The minimum value is calculated for case (2) when the hot block is placed between the two insulated walls. The increase in Reynolds and Hartmann numbers enhances the heat transfer and the total entropy generation. In addition, the nanoparticle diameter increase reduces the heat transfer and the irreversibility, the impact of the magnetic field inclination angle on the heat transfer and the total entropy generation is investigated, and the Brownian motion enhances the heat transfer and the total entropy generation.

Źródło:

Acta Mechanica et Automatica; 2022, 16, 4; 417--431
1898-4088
2300-5319

Pojawia się w:

Acta Mechanica et Automatica

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 15.

Tytuł:

Experimental Analysis of Horizontal Turbulence of Flow over Flat and Deformed Beds

Autorzy:

Termini, D.

Powiązania:

https://bibliotekanauki.pl/articles/241285.pdf

Data publikacji:

2015

Wydawca:

Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN

Tematy:

open-channel flow
flow turbulence structure
burst cycle
bed forms
laboratory experiments

Opis:

Laboratory experiments in a straight flume were carried out to examine the evolution of large-scale horizontal turbulent structures under flat-bed and deformed-bed conditions. In this paper, the horizontal turbulence of flow under these conditions is analyzed and compared. The conditioned quadrant method is applied to verify the occurrence of turbulent events. The distributions of horizontal Reynolds shear stress and turbulent kinetic energy are also presented and discussed. Results show the occurrence of an “initial” sequence of horizontal vortices whose average spatial length scales with the channel width. Under deformed-bed conditions, this spatial length does not change.

Źródło:

Archives of Hydro-Engineering and Environmental Mechanics; 2015, 62, 3-4; 77-99
1231-3726

Pojawia się w:

Archives of Hydro-Engineering and Environmental Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 16.

Tytuł:

A turbulence model for 3-d flows with anisotropic structure of turbulence

Autorzy:

Czernuszenko, W.
Rylov, A.

Powiązania:

https://bibliotekanauki.pl/articles/241364.pdf

Data publikacji:

2005

Wydawca:

Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN

Tematy:

3D flow
mathematical model
numerical simulation
open channel flow
turbulence model

Opis:

A new turbulence model for flows in open channels with compound cross-sections is presented. The structure of turbulence in these channels can be anisotropic. This structure is described by the turbulent stress tensor that is presented here as the sum of two tensors, namely, normal and shear stress tensors. The normal and shear turbulent stresses are expressed by the turbulence intensities and the mixing length tensor (MLT), respectively. The turbulence intensities can be learned from measurements or another suitable approaches. One such approach that allows calculating the main component of the normal stresses is presented in the paper. The components of MLT are defined based on a new concept of generic mixing length (GML). The generic mixing length is assumed to depend on both distances; from the nearest wall and from the water surface. To demonstrate how the new model works the basic hydrodynamic equations (parabolic approximation of Reynolds equations) together with the turbulence model are solved. The well-known Patankar and Spalding (1972) algorithm was used when solving these equations. A series of numerical simulations were performed for different components of MLT and different channel geometries.

Źródło:

Archives of Hydro-Engineering and Environmental Mechanics; 2005, 52, 4; 303-320
1231-3726

Pojawia się w:

Archives of Hydro-Engineering and Environmental Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 17.

Tytuł:

Hydraulic Loss Coefficients in 1D Flows

Autorzy:

Sawicki, J. M.

Powiązania:

https://bibliotekanauki.pl/articles/241418.pdf

Data publikacji:

2007

Wydawca:

Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN

Tematy:

hydraulic loss
closed-conduits flows
water hammer
open channel flow

Opis:

Determination of hydraulic losses is a very important problem, both from the cognitive and practical points of view. For the uniform and steady fluid streams these losses are described by the well known algebraic expressions, containing some experimental coefficients. In technical practice it is commonly assumed, that these coefficients can be applied also for more complex kinds of flow (non-uniform and even unsteady). However, the problem analysis shows that the proper level of conformity between the results of calculations and measurements can be obtained only after a considerable enlargement of the loss coefficient. Investigation of available characteristics of non-uniform and unsteady 1D velocity fields, presented in this article, leads to the conclusion that this enlargement is physically justified and in some cases it is possible to determine correction factors, which enable recalculation of "basic" coefficients into their new values, suitable for more complex models of 1D flows.

Źródło:

Archives of Hydro-Engineering and Environmental Mechanics; 2007, 54, 2; 95-116
1231-3726

Pojawia się w:

Archives of Hydro-Engineering and Environmental Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 18.

Tytuł:

Validation of a flow channel to investigate velocity profiles of friction-reducing ship coatings

Autorzy:

Weisheit, J.
Schneider, V. E.
Serr, J. M.
Hagemeister, N.
Oeffner, J.

Powiązania:

https://bibliotekanauki.pl/articles/1841545.pdf

Data publikacji:

2021

Wydawca:

Uniwersytet Morski w Gdyni. Wydział Nawigacyjny

Tematy:

ship coatings
flow Channel
vessel velocity
laser Doppler velocimeter
computational fluid dynamics
AIRCOAT project
reynolds averaged navier stokes
measurement volume

Opis:

Reducing friction with specialised hull coatings or air lubrication technologies has a potential reducing energy consumption and emissions in shipping. The EU project AIRCOAT combines both by developing a passive air lubrication technology inspired by nature that is implemented on a self-adhesive foil system. Besides validating the friction reduction it is of high interest to understand the underlying mechanism that causes the reduction. Therefore, a flow channel was designed, that creates a stationary turbulent flow within a square duct allowing for non-invasive measurements by laser doppler velocimetry. The high spatial resolution of the laser device makes recording velocity profiles within the boundary layer down to the viscous sublayer possible. Determination of the wall shear stress τ enables direct comparison of different friction reduction experiments. In this paper we validate the methodology by determining the velocity profile of the flat channel wall (without coatings). We further use the results to validate a CFD model in created in OpenFOAM. We find that velocities along the longitudinal axis are generally in good agreement between numerical and experimental investigations.

Źródło:

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2021, 15, 1; 225-231
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: 19.

Tytuł:

The application of cumulants to flow routing

Autorzy:

Romanowicz, Renata J.
Doroszkiewicz, Joanna

Powiązania:

https://bibliotekanauki.pl/articles/108562.pdf

Data publikacji:

2019

Wydawca:

Instytut Meteorologii i Gospodarki Wodnej - Państwowy Instytut Badawczy

Tematy:

open channel flow
linearized St. Venant equation
analytical solutions
moments
cumulants

Opis:

This paper aims to fill a gap between present and past research approaches to modelling flow in open channels. In particular, a history of the analytical solutions of a linearized St. Venant equation is presented. A solution of the linearized St. Venant equation, describing the response of a river channel to a single impulse forcing, the so called Instantaneous Unit Hydrograph (IUH), can be described using cumulants, defined as the moments of a logarithm of a variable. A comparison of analytical and numerical solutions of flood wave propagation under various flow conditions is given. The river reach of Biała Tarnowska is used as an illustration of both approaches. A practical application of simplified solutions to the emulator of a flood wave propagation is suggested showing a link between theory and practice.

Źródło:

Meteorology Hydrology and Water Management. Research and Operational Applications; 2019, 7, 1; 15-21
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: 20.

Tytuł:

The effect of temperature-dependent viscosity and thermal conductivity on velocity and temperature field: an analytical solution using the perturbation technique

Autorzy:

Panahi-Kalus, H.
Ahmadinejad, M.
Moosaie, A.

Powiązania:

https://bibliotekanauki.pl/articles/38610956.pdf

Data publikacji:

2020

Wydawca:

Instytut Podstawowych Problemów Techniki PAN

Tematy:

temperature-dependent material properties
laminar channel flow
anaytical solution
perturbation technique

Opis:

This paper proposes a general form of the perturbation expansion method for the governing equations of viscous flow coupled to the temperature evolution. The effect of the variations of viscosity and thermal conductivity with temperature on the temperature and velocity fields in a steady two-dimensional Couette–Poiseuille flow is examined. The presented analytical solution by the perturbation method is validated against a finite difference solution of the governing equations. The numerical and analytical solutions are in good agreement.

Źródło:

Archives of Mechanics; 2020, 72, 6; 555-576
0373-2029

Pojawia się w:

Archives of Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 21.

Tytuł:

Numerical study on two dimensional distribution of streamwise velocity in open channel turbulent flows with secondary current effect

Autorzy:

Mohan, S.
Kundu, S.
Ghoshal, K.
Kumar, J.

Powiązania:

https://bibliotekanauki.pl/articles/38616700.pdf

Data publikacji:

2021

Wydawca:

Instytut Podstawowych Problemów Techniki PAN

Tematy:

velocity distribution
open channel flow
turbulent flow
RANS equations
secondary current
finite difference method

Opis:

For studying mechanism of sediment transport in river flows, open channel flow is a prototype. Flow has always three components of velocity for all types of channel geometry and for a time independent uniform flow along streamwise or main flow direction, all the components of velocity are functions of lateral and vertical coordinates. The present study investigates the two dimensional distribution of streamwise (or longitudinal) velocity starting from the Reynolds averaged Navier–Stokes equation for a turbulent open channel flow which is steady and uniform along the main flow direction. Secondary flows both along the vertically upward direction and along the lateral direction are considered which are also taken as functions of lateral and vertical coordinates. Inclusion of the secondary current brings the effect of dip phenomenon in the model. The resulting second order partial differential equation is solved numerically. The model is validated for all the cross-sectional, transverse and centreline velocity distribution by comparing with existing relevant set of experimental data and also with an existing model. Comparison results show good agreement with data as well as with the previous model proving the efficiency of the model. It is found that the transverse velocity distribution depends on the formation of circular vortex in the cross-sectional plane and becomes periodic as the number of circular vortex increases for increasing aspect ratios.

Źródło:

Archives of Mechanics; 2021, 73, 2; 175-200
0373-2029

Pojawia się w:

Archives of Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 22.

Tytuł:

Numerical simulation of the micropolar fluid flow and heat transfer in a channel with a shrinking and a stationary wall

Autorzy:

Ali, K.
Ashraf, M.

Powiązania:

https://bibliotekanauki.pl/articles/949324.pdf

Data publikacji:

2014

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

channel flow
shrinking/stationary walls
couple stress
quasi-linearization
Joule heating
viscous dissipation

Opis:

We present the numerical study of hydromagnetic (MHD) flow and heat transfer characte- ristics of a viscous incompressible electrically conducting micropolar fluid in a channel with one wall shrinking and the other at rest in the presence of a transverse applied magnetic field. Different from the classical shooting methodology, we employ a combination of a di- rect and an iterative method (SOR with optimal relaxation parameter) for solving the sparse systems of linear algebraic equations arising from the FD discretization of the linearized self similar nonlinear ODEs. Effects of some physical parameters on the flow and heat transfer are discussed and presented through tables and graphs. The present investigation may be beneficial to the flow and thermal control of polymeric processing.

Źródło:

Journal of Theoretical and Applied Mechanics; 2014, 52, 2; 557-569
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 23.

Tytuł:

Koncepcja stanowiska do badania wypływu zanieczyszczeń z kanałów burzowych
Concept of an experimental stand for study the outflow of pollutants from combined sewer overflows

Autorzy:

Rząsa, M. R.
Boguniewicz-Zabłocka, J.

Powiązania:

https://bibliotekanauki.pl/articles/268350.pdf

Data publikacji:

2015

Wydawca:

Politechnika Gdańska. Wydział Elektrotechniki i Automatyki

Tematy:

przepływ w kanale otwartym
przepływ dwufazowy
komputerowa analiza obrazu
open channel flow
two-phase flow
computer image processing

Opis:

Pomiary przepływu mieszaniny polidyspersyjnej są jednymi z najtrudniejszych do zrealizowania w warunkach technicznych. W artykule opisano koncepcję systemu pomiarowego, który umożliwi obserwację przepływającej mieszaniny oraz wyznaczenia podstawowych parametrów jej ruchu. W pracy zaproponowano sposób opisu wydmy przesuwającego się piasku. Wymiary wydmy zdefiniowano za pomocą czterech charakterystycznych wymiarów. Zaproponowano stanowisko laboratoryjne umożliwiające badanie przepływu mieszaniny w kanale otwartym przy różnym nachyleniu kanału i różnym składzie granulometrycznym frakcji stałej. Stanowisko wyposażono w system rejestracji obrazu. Obrazy zarejestrowane kamerą poddawane są procesowi komputerowej analizy obrazu i na tej podstawie możliwe jest określenie podstawowych parametrów ruchu mieszaniny. Praca zawiera opis koncepcji stanowiska laboratoryjnego oraz ideę metody analizy obrazu.
A storm water system with open channels for the discharge of rainwater exists in most urbanised areas. The flow in these kind of channels is generally multiphase flow, in which there are solids and liquids and in some places there may be an additional gas phase. Therefore the ability to describe such flow is reduces to the description of the motion of the polydisperse mixture. Polydisperse mixture flow measurements are among the most difficult to achieve in technical terms. The article describes the concept of a measurement system that allows observation of the poly-dispersed flow and determine the basic parameters of its motion. Concept of experimental laboratory set-up was proposed to measure the parameters of the polydispersed mixture flow process in open channel with different slope of the channel and various granulometry of the solid fraction. In this work description of sand dunes with four typical parameters was proposed. A digital camera is used to interrogate the flow. Images recorded on the camera will be subjected to a process of image analysis, and from this the basic parameters of the movement are determined. The work includes a description of the experimental set-up with the idea of image analysis methods.

Źródło:

Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej; 2015, 47; 155-158
1425-5766
2353-1290

Pojawia się w:

Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 24.

Tytuł:

Impact of transversely-oriented wall corrugation on hydraulic resistance of a channel flow
Wpływ poprzecznego pofalowania ścian na opory hydrauliczne przepływu w kanale

Autorzy:

Szumbarski, J.
Blonski, S.
Kowalewski, T. A.

Powiązania:

https://bibliotekanauki.pl/articles/139979.pdf

Data publikacji:

2011

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

przepływ w kanale
opory hydrauliczne
ściany pofalowane
metody numeryczne
channel flow
hydraulic resistance
corrugated walls
numerical methods

Opis:

The impact of the transversely-oriented sinusoidal wall corrugation on the hydraulic drag is investigated numerically for the flow through the channel of finite width and with flat sidewalls. The numerical method, based on the domain transformation and Chebyshev-Galerkin discretization, is used to investigate the flow resistance of the laminar, parallel and pressure-driven flow. The obtained results are compared to the reference case, i.e., to the flow through the channel with rectangular cross section of the same aspect ratio. Simple explanation of the gain in the volumetric flow rate observed in the flow through spanwise-periodic channel with long-wave transversely-oriented wall corrugation is provided. In the further analysis, pressure drop in the flows with larger Reynolds numbers are studied numerically by means of the finite-volume commercial package Fluent. Preliminary experimental results confirm the predicted tendency.
Przedmiotem artykułu jest analiza numeryczna wpływu poprzecznego sinusoidalnego pofalowania ścian na opory hydrauliczne przepływu cieczy lepkiej w kanale. Do wyznaczenia stacjonarnego pola ruchu cieczy lepkiej w kanale posłużono się transformacją obszaru i spektralną metodą Czebyszewa-Galerkina. Obliczone wartości strat ciśnienia porównano z przepływem laminarnym w kanale o ścianach płaskich i przekroju prostokątnym, przy zachowaniu takiej samej wartości stosunku szerokości kanału do jego wysokości. Podano objaśnienie efektu zmiejszenia oporów hydraulicznych w przypadku poprzecznego pofalowania o dużej długości fali. Omówiono również wyniki analizy wpływu pofalowania ścian na straty ciśnienia dla przepływów z większymi liczbami Reynoldsa, uzyskane przy pomocy komercyjnego programu Fluent. Przedstawiono wstępne wyniki badań eksperymentalnych, które potwierdzają zależności otrzymane w modelach numerycznych.

Źródło:

Archive of Mechanical Engineering; 2011, LVIII, 4; 441-466
0004-0738

Pojawia się w:

Archive of Mechanical Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 25.

Tytuł:

Static instability of an inverted plate in channel flow: state-space representation and solution approximation

Autorzy:

Li, P.
Zhang, D.
Cui, J.
Yin, H.
Yang, Y.

Powiązania:

https://bibliotekanauki.pl/articles/38697113.pdf

Data publikacji:

2023

Wydawca:

Instytut Podstawowych Problemów Techniki PAN

Tematy:

inverted cantilevered plate
static aeroelastic instability
channel flow
state-space representation
Glauert’s series
the least squares method

Opis:

Plate-like structures in channel flow are commonly found in engineering. This paper reports a theoretical study on the static aeroelastic instability of an inverted cantilevered plate in an inviscid channel flow through the state space. This study begins with the kernel function of the flow potential determined in the Fourier domain with the help of the mirror image method. Then, the instability equation is derived from the operator theory and transformed in the state space. Finally, with Glauert’s expansion, model functions, and error functions, the instability problem of such a plate has been modeled as a mathematical function approximation problem and solved by the least squares method. The derived instability equation is considered at the continuum level of description, and no approximation appears at the first equation level. The convergence and reliability of the proposed modeling and its solutions approximation are entirely tested, and it can successfully predict the instability boundary, behavior, and the channel effect. Numerical results show that the decreased channel height and asymmetric plate placement in the channel significantly decrease the critical flow velocity. The plate instability modes are close to the plate’s first natural ones and not sensitive to the channel parameters. This conclusion allows further theoretical exploration of a semi-analytical approximation of the instability boundary from the obtained instability equation. The current modeling strategy in a continuum sense may provide a new idea and essential reference for other instability problems.

Źródło:

Archives of Mechanics; 2023, 75, 6; 695-727
0373-2029

Pojawia się w:

Archives of Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 26.

Tytuł:

Numerical simulation of channel flow over a skewed equilateral cavity

Autorzy:

Kamel, Abanoub G.
Haraz, Eman H.
Hanna, Sarwat N.

Powiązania:

https://bibliotekanauki.pl/articles/1839759.pdf

Data publikacji:

2020

Wydawca:

Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej

Tematy:

finite difference method
incompressible flow
channel flow
lid-driven
shear-driven
skewed cavity
Navier-Stokes equations
równanie Naviera-Stokesa
przepływ nieściśliwy
metoda różnic skończonych
przepływ kanałowy

Opis:

In this paper, an incompressible, two-dimensional (2D), time-dependent, Newtonian, laminar, and internal channel fluid flow over a skewed equilateral cavity is simulated using the finite difference method (FDM) and alternating direction implicit (ADI) technique. Navier-Stokes equations are solved numerically in stream function-vorticity formulation. The goal of tackling this problem depends on its academic significance by studying the difference between lid-driven and shear-driven cavity flows in terms of the formation of Moffatt eddies at the sharp corner, also to obtain the length and intensity ratios of these counter-rotating vortices. The value of velocity components along the centerlines of the skewed cavity was revealed at low and intermediate Reynolds numbers (Re), typically (Re = 200 and 2000) at two different skew angles of mainly 30° and 45°. Likewise, the blocked-off regions’ method is used to deal with the geometry of the skewed cavity especially the sharp corners. Furthermore, as Re increases, the main vortex approaches the skewed cavity center and the counter-rotating vortices get bigger in size and intensity, and their number increases.

Źródło:

Journal of Applied Mathematics and Computational Mechanics; 2020, 19, 3; 29-43
2299-9965

Pojawia się w:

Journal of Applied Mathematics and Computational Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 27.

Tytuł:

A Mathematical Model of Membrane Gas Separation with Energy Transfer by Molecules of Gas Flowing in a Channel to Molecules Penetrating this Channel from the Adjacent Channel

Autorzy:

Szwast, M.
Szwast, Z.

Powiązania:

https://bibliotekanauki.pl/articles/185043.pdf

Data publikacji:

2015

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

membrane
membrane module
reciprocal transfer of energy between gas molecules
changes of the pressure of gas along the length of flow channel
membrana
wzajemne przekazywanie energii między cząsteczkami gazu
zmiany ciśnienia gazu na długości kanału przepływowego

Opis:

The paper presents the mathematical modelling of selected isothermal separation processes of gaseous mixtures, taking place in plants using membranes, in particular nonporous polymer membranes. The modelling concerns membrane modules consisting of two channels – the feeding and the permeate channels. Different shapes of the channels cross-section were taken into account. Consideration was given to co-current and counter-current flows, for feeding and permeate streams, respectively, flowing together with the inert gas receiving permeate. In the proposed mathematical model it was considered that pressure of gas changes along the length of flow channels was the result of both – the drop of pressure connected with flow resistance, and energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel. The literature on membrane technology takes into account only the drop of pressure connected with flow resistance. Consideration given to energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel constitute the essential novelty in the current study. The paper also presents results of calculationsobtained by means of a computer program which used equations of the derived model. Physicochemical data concerning separation of the CO2/CH4 mixture with He as the sweep gas and data concerning properties of the membrane made of PDMS were assumed for calculations.

Źródło:

Chemical and Process Engineering; 2015, 36, 2; 151-169
0208-6425
2300-1925

Pojawia się w:

Chemical and Process Engineering

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 28.

Tytuł:

Instability of viscous incompressible flow in a channel with transversely corrugated walls
Zjawisko destabilizacji przepływu laminarnego w kanale z poprzecznie pofalowanymi ścianami

Autorzy:

Szumbarski, J.

Powiązania:

https://bibliotekanauki.pl/articles/279211.pdf

Data publikacji:

2007

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

wavy channel
laminar flow
linear stability

Opis:

Destabilization of the laminar flow in a channel with transversly wavy walls is investigated. The basic flow is determined by a semi-analytical method based on the concept of immersed boundaries. The stability equations are discretized by the spectrally accurate Chebyshev-tau method. It is demonstrated that the transversal wall waviness can be used in order to achieve destabilization of the laminar flow at low Reynolds numbers. Possible applications include the improvement of mixing and heat/mass transfer in various devices used in heat technology, biotechnology and medicine.
Praca poświęcona jest zjawisku destabilizacji przepływu laminarnego w kanale wywołanej poprzecznym pofalowaniem ścian. Przepływ niezaburzony wyznaczono przy pomocy semi-analitycznej metody zanurzonych granic. Wyprowadzono równania stateczności, które następnie poddano dyskretyzacji przy użyciu wielomianów Czebyszewa. Pokazano, że poprzeczne pofalowanie ścian o odpowiedniej geometrii prowadzi do destabilizacji przepływu przy niskich liczbach Reynoldsa i omówiono własności pola zaburzeń. Wydaje się, że opisany efekt może mieć znaczenie dla intensyfikacji mieszania i poprawy efektywności procesów transportu w technice cieplnej, biotechnologii i medycynie.

Źródło:

Journal of Theoretical and Applied Mechanics; 2007, 45, 3; 659-683
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 29.

Tytuł:

Experimental and numerical analysis of the air flow in T-shape channel flow
Eksperymentalna i numeryczna analiza przepływu powietrza przez skrzyżowanie kanałów w kształcie litery T

Autorzy:

Szmyd, J.
Branny, M.
Karch, M.
Wodziak, W.
Jaszczur, M.
Nowak, R.

Powiązania:

https://bibliotekanauki.pl/articles/219603.pdf

Data publikacji:

2013

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

przepływ przez skrzyżowanie kanałów o kształcie T
PIV
walidacja kodów CFD
wentylacja kopalń
T-shape channel flow
validation of CFD codes
mining ventilation

Opis:

This paper presents the results of experimental and numerical investigations of air flow through the crossing of a mining longwall and ventilation gallery. The object investigated consists of airways (headings) arranged in a T-shape. Maintained for technological purposes, the cave is exposed particularly to dangerous accumulations of methane. The laboratory model is a certain simplification of a real longwall and ventilation gallery crossing. Simplifications refer to both the object’s geometry and the air flow conditions. The aim of the research is to evaluate the accuracy with which numerical simulations model the real flow. Stereo Particle Image Velocimetry (SPIV) was used to measure all velocity vector components. Three turbulence models were tested: standard k-ε, k-ε realizable and the Reynolds Stress Model (RSM). The experimental results have been compared against the results of numerical simulations. Good agreement is achieved between all three turbulence model predictions and measurements in the inflow and outflow of the channel. Large differences between the measured and calculated velocity field occur in the cavity zone. Two models, the standard k-ε and k-ε realizable over-predict the measure value of the streamwise components of velocity. This causes the ventilation intensity to be overestimated in this domain. The RSM model underestimates the measure value of streamwise components of velocity and therefore artificially decreases the intensity of ventilation in this zone. The RSM model provides better predictions than the standard k-ε and k-ε realizable in the cavity zone.
Przedmiotem badań jest walidacja wybranych modeli CFD (Computational Fluid Dynamics) przy przepływie powietrza przez laboratoryjny model skrzyżowania kanałów w kształcie litery T. Stanowisko laboratoryjne przedstawia uproszczony model skrzyżowania ściany z chodnikiem wentylacyjnym. Przyjęto, że przepływ powietrza jest ustalony i izotermiczny. Dla tych warunków z równości liczb Reynoldsa w modelu i obiekcie rzeczywistym wynika warunek podobieństwa uśrednionych pól prędkości (przy załozeniu nieściśliwości powietrza). Pomiar składowych wektora prędkości wykonano metodą SPIV (Stereo Particle Image Velocimetry). W pracy testowano trzy modele turbulencji: standardowy model k-ε, jego modyfikację k-ε „realizable” oraz model naprężeń Reynoldsa (Reynolds Stress Model). Obliczenia numeryczne dla warunków identycznych jak w eksperymencie wykonano przy zastosowaniu programu FLUENT. Zadawalającą zgodność pomiędzy pomiarami i obliczeniami wszystkimi trzema modelami turbulencji uzyskano w kanałach zarówno po stronie dopływu jak i wypływu strumieniem powietrza ze skrzyżowania. Natomiast w strefie wnęki żaden z testowanych modeli nie wykazał pełnej zgodności z wynikami eksperymentalnymi. Do oszacowania dokładności z jaką symulacje numeryczne odwzorowują przepływ rzeczywisty w strefie wnęki wykorzystano wskaźnik charakteryzujący czas zaniku cząstek znacznikowych wprowadzonych do przepływu. Obliczenia wykonano dla dwóch modeli turbulencji: standardowego k-ε oraz modelu RSM. Czas potrzebny do rozrzedzenia początkowej koncentracji gazu znacznikowego do określonego poziomu - w przedziale koncentracji względnej od 0,3 do 0,1 - uzyskany z obliczeń standardowym modelem k-ε jest krótszy o 32%-27% od czasu wynikającego z pomiarów podczas gdy model RSM przeszacowuje wartości mierzone wartości koncentracji gazu o 18%-27%. Dwa z testowanych modeli, mianowicie standardowy k-ε i k-ε „realizable” przeszacowują mierzone wartości składowych wzdłużnych wektora prędkości. Konsekwencją tego jest sztuczne zawyżenie intensywności wentylacji we wnęce. Z kolei model RSM niedoszacowuje mierzone wartości składowych wzdłużnych wektora prędkości co powoduje zaniżenie rzeczywistej intensywności wentylacji tej strefy. Z przeprowadzonych badań wynika, że w obszarze wnęki rezultaty uzyskane modelem RSM są bliższe do wartości mierzonych niż prognozowane standardowym modelem k-ε i modelem k-ε „realizable”.

Źródło:

Archives of Mining Sciences; 2013, 58, 2; 333-348
0860-7001

Pojawia się w:

Archives of Mining Sciences

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 30.

Tytuł:

Simulation of laminar flow passing through a T-splitter plate and bridge pier.

Autorzy:

Qasim, Rafi Mohammed
Jabbar, Tahseen Ali
Faisal, Safaa Hameed

Powiązania:

https://bibliotekanauki.pl/articles/36063658.pdf

Data publikacji:

2023

Wydawca:

Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Wydawnictwo Szkoły Głównej Gospodarstwa Wiejskiego w Warszawie

Tematy:

hydrodynamic
laminar flow
open channel
pier
splitter plate

Opis:

The present analysis focuses on the investigation of the two-dimensional flow passing a bridge pier nearby a splitter plate in different regimes of a laminar flow. The splitter plate is T-shaped and two different cases have been studied based on the form of the splitter plate relative to the bridge pier. The analysis is implemented for steady and incompressible water flow in an open channel. The current study deals with velocity vectors, drag coefficients, lift coefficients, and skin friction. The analysis of the velocity vector gave a good indicator about the separation process and dissipation, which occurs at the splitter plate before the occurrence of these processes at the front face of the pier, especially the flow separation process. Moreover, the velocity vector gave a good image about the flow direction at two regions, the first region is located between the rear portion of the splitter plate and the frontal face of the pier, while the second region is the wake region, which is located at the downstream of the pier. Negative drag coefficient, lift coefficient, and skin friction coefficient values are obtained from the analysis. This happens due to the existence of the splitter plate that leads to the reduction of these values.

Źródło:

Scientific Review Engineering and Environmental Sciences; 2023, 32, 2; 135-154
1732-9353

Pojawia się w:

Scientific Review Engineering and Environmental Sciences

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 31.

Tytuł:

Comparison of Average Energy Slope Estimation Formulas for One-dimensional Steady Gradually Varied Flow

Autorzy:

Artichowicz, W.
Mikos-Studnicka, P.

Powiązania:

https://bibliotekanauki.pl/articles/241083.pdf

Data publikacji:

2014

Wydawca:

Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN

Tematy:

open channel
steady flow
gradually varied flow
standard step method
energy slope

Opis:

To find the steady flow water surface profile, it is possible to use Bernoulli’s equation, which is a discrete form of the differential energy equation. Such an approach requires the average energy slope between cross-sections to be estimated. In the literature, many methods are proposed for estimating the average energy slope in this case, such as the arithmetic mean, resulting in the standard step method, the harmonic mean and the geometric mean. Also hydraulic averaging by means of conveyance is commonly used. In this study, water surface profiles numerically computed using different formulas for expressing the average slope were compared with exact analytical solutions of the differential energy equation. Maximum relative and mean square errors between numerical and analytical solutions were used as measures of the quality of numerical models. Experiments showed that all methods gave solutions useful for practical engineering purposes. For every method, the numerical solution was very close to the analytical one. However, from the numerical viewpoint, the differences between the methods were significant, as the errors differed up to two orders of magnitude.

Źródło:

Archives of Hydro-Engineering and Environmental Mechanics; 2014, 61, 3-4; 89--109
1231-3726

Pojawia się w:

Archives of Hydro-Engineering and Environmental Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 32.

Tytuł:

Cash flow sensitivity of investment: Evidence from the Polish listed companies

Autorzy:

Nehrebecki, Marian

Powiązania:

https://bibliotekanauki.pl/articles/1356332.pdf

Data publikacji:

2020-10-28

Wydawca:

Uniwersytet Warszawski. Wydział Nauk Ekonomicznych

Tematy:

investment
cash flow
ICFS
balance sheet channel
financial accelerator

Opis:

The paper focuses on assessment of the sensitivity of investment on cash flow (ICFS) made by listed companies in Poland. Achieving this goal will also involve analysing and drawing conclusions about the balance-sheet channel of monetary transmission. An empirical part uses data from financial statements for Poland derived from Emerging Markets Information Services (EMIS), related to companies listed on the Warsaw Stock Exchange and NewConnect. Estimations were made using the Ordinary Least Squares method with robust standard errors, and results made it clear that cash flow has a positive significant impact, indicating that most companies operate on the imperfect and incomplete market, and with constrained or costly access to external financing. Further, it is found that the impact is significantly strong in the slowdown, as financial constraints are more binding. These results seem to confirm that the balance-sheet channel of monetary transmission is operative in Poland.

Źródło:

Central European Economic Journal; 2020, 7, 54; 157 - 171
2543-6821

Pojawia się w:

Central European Economic Journal

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 33.

Tytuł:

Sand- and mud-filled fluvial palaeochannels in the Wielkopolska Member of Neogene Poznań Formation, central Poland

Autorzy:

Widera, M.

Powiązania:

https://bibliotekanauki.pl/articles/191168.pdf

Data publikacji:

2013

Wydawca:

Polskie Towarzystwo Geologiczne

Tematy:

fluvial lithosomes
floodplain deposits
channel-fill facies
channel width-depth ratio
hyperconcentrated flow
anastomosing river system

Opis:

This study focuses on the single- and multi-storey fluvial palaeochannel lithosomes encased in mud- rich floodplain deposits in the alluvial succession of the late Neogene Wielkopolska Member of the Poznań For- mation, central Poland, well-exposed in the lignite mining pits of the region. The fluvial lithosomes include both sand-filled and mud-filled channel varieties. The channel-fill facies are not diagnostic for any particular type of fluvial system, as the fine- to very fine-grained sandy deposits are massive to trough cross-stratified and also the muddy deposits are massive to weakly flat-laminated. The scarcity of lateral accretion bedding precludes the possibility of meandering rivers, whereas the low width/thickness ratios of the palaeochannels preclude braided rivers. The width/thickness ratio is in the range of 4.5–14 (averaging 7.5) for sand-filled channels and in the range of 6–10 (averaging 9) for mud-filled ones, which indicates narrow ribbons in general classification of fluvial channel belts. The origin of the alluvial succession is attributed to a W-/NW-directed anastomosing river system characterized by laterally inactive cut-and-fill channels with cohesive and vegetated banks. The sand-filled chan- nels conveyed water and sediment discharges on a perennial basis, whereas the mud-filled conduits are thought to have been the cut-and-abandoned branches of the system, filled by overbank flooding from adjacent active channels. Minor lateral migration of channels occurred probably during periods of minimum subsidence rate, when the fluvial system was forced to develop lateral accommodation for its discharges.

Źródło:

Annales Societatis Geologorum Poloniae; 2013, 83, 1; 19-28
0208-9068

Pojawia się w:

Annales Societatis Geologorum Poloniae

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 34.

Tytuł:

Wpływ warstwy MAC standardu 802.11 na osiągane parametry QoS
Impact of the MAC Layer of the Standard 802.11 on the Achieved QoS

Autorzy:

Dolińska, Iwona
Masiukiewicz, Antoni

Powiązania:

https://bibliotekanauki.pl/articles/439897.pdf

Data publikacji:

2013

Wydawca:

Akademia Finansów i Biznesu Vistula

Tematy:

standard IEEE 802.11
warstwa MAC
QoS transmisji
przepływność kanału radiowego
IFS
MAC layer
transmission quality of service (QoS)
radio channel flow capacity
inter-frame spacing (IFS)

Opis:

Podstawowym parametrem sieci WLAN jest przepustowość transmisji. Zdefiniowane w standardzie przepustowości maksymalne teoretyczne są w warunkach rzeczywistych ograniczane z jednej strony jakością kanału transmisyjnego, a z drugiej sposobem działania samego standardu. W przypadku standardu IEEE 802.11 zastosowana metoda komunikacji DCF wprowadza obowiązkowe przerwy w nadawaniu – interwały czasowe IFS, które powodują zmniejszenie przepustowości osiąganej w jednostce czasu. W artykule omówiono różne ulepszenia metody DCF, zaproponowane w wyniku prac naukowo-badawczych. Porównano je pod względem przydatności w rzeczywistych zastosowaniach.
The basic parameter of the WLAN is transmission output. The defined in the standard of output capacity maximum theoretical values are in the real conditions limited, on the one hand, by the transmission channel quality and, on the other hand, by the way in which the very standard acts. In the case of standard IEEE 802.11, the applied method of communication DCF (distributed coordination function) introduces the obligatory pauses in broadcasting – temporal intervals IFS which cause a reduction of the output capacity achieved in a time unit. In their article, the authors discussed various improvements of the DCF method proposed in result of research works. They are compared in terms of their usefulness in the real applications.

Źródło:

Kwartalnik Naukowy Uczelni Vistula; 2013, 4(38); 88-102
2084-4689

Pojawia się w:

Kwartalnik Naukowy Uczelni Vistula

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 35.

Tytuł:

Analysis of controlled molecular dynamic flow in a channel with non-equal inlet and outlet cross-sectional areas

Autorzy:

Najafi, H. R.
Karimian, S. M. H.

Powiązania:

https://bibliotekanauki.pl/articles/279977.pdf

Data publikacji:

2017

Wydawca:

Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej

Tematy:

molecular dynamics
nano-channel
steady flow
non-equal inlet and outlet
pressure

Opis:

Thermo-fluid properties are required for numerical modeling of nano/micro devices. These properties are mostly obtained from the results of molecular dynamics (MD) simulations. Therefore, efforts have been made to develop methods for numerical evaluation of fluid properties such as pressure and velocity. One of the main challenges faced by numerical simulations is to simulate steady molecular flow in channels with non-equal inlet and outlet boundaries. Currently, periodic boundary conditions at the inlet and outlet boundaries are an inevitable condition in many steady flow molecular dynamics simulations. As a result, a nano-channel with different cross sectional areas at the inlet and outlet could not be simulated easily. Here, a method is presented to generate and control steady molecular flow in a nano-channel with different cross sectional areas at the inlet and outlet. The presented method has been applied to a converging-diverging channel, and its performance has been studied through qualitative and quantitative representation of flow properties.

Źródło:

Journal of Theoretical and Applied Mechanics; 2017, 55, 4; 1141-1153
1429-2955

Pojawia się w:

Journal of Theoretical and Applied Mechanics

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 36.

Tytuł:

Peristaltic flow of a third grade fluid accounting Joule heating and Magnetic field. Effects in an asymmetric channel

Autorzy:

Asha, S. K.
Deepa, C. K.

Powiązania:

https://bibliotekanauki.pl/articles/1046550.pdf

Data publikacji:

2019

Wydawca:

Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN

Tematy:

ADM
Joule heating
MHD third grade fluid
Peristaltic flow
asymmetric channel

Opis:

In this article, we have analysed the MHD third grade fluid flow induced by a peristaltic wave. The flow is analysed using the lubrication approximations. The reduced equations are solved by Adomian Decomposition Method (ADM) and the expressions for stream function, velocity, pressure gradient and frictional force are obtained. The effect of pertinent parameters such as Brinkmann number, magnetic field, Deborah number and phase difference are analysed and illustrated graphically. The results shown that the rate of conduction of heat enhances by supplying heat to the channel. Also it is noticed that by increasing magnetic field the Lorentz forces reduces the velocity. This study finds application in various practical devices like electric power generators, heaters and conductors.

Źródło:

World Scientific News; 2019, 137; 1-17
2392-2192

Pojawia się w:

World Scientific News

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 37.

Tytuł:

Cross-waves and pulsating flows in the side-channel spillway - an experimental approach

Autorzy:

Azmeri, Azmeri
Ummah, Chairatun
Jemi, Faris Zahran
Faudli, Imam
Nasaiy, Qurratul 'Aini Benti

Powiązania:

https://bibliotekanauki.pl/articles/2203528.pdf

Data publikacji:

2023

Wydawca:

Instytut Technologiczno-Przyrodniczy

Tematy:

cross-waves
hydrodynamic force
physical model
pulsating flow
side-channel spillway

Opis:

Potentially hazardous side-channels of complex geometry need to be investigated using detailed hydraulic physical models. This study aims to analyse the cross-waves pattern and pulsating flow using a side-channel spillway physical model. This study compares the cross-waves pattern were measured using an experimental installation set to generate cross-waves on the surface (original series) with another structure that did not produce cross-waves (modified series). The results showed that the geometry of the left wall caused instability in flow patterns and secondary flows. The starting point of Q2 discharge was detected by minor turbulence on the water surface near the left wall at a water depth of 3.3 m at the starting point of the wall, but with no overtopping. Cross-waves formed downstream at the right wall crosswise, lower than at the left wall. The height of the cross-wave increased substantially from Q100 to Q1000 discharges leading to overtoppings near the left wall at a water depths of 4.2 and 5.0 m at the starting point of the wall, and near the right wall at a water depths of 3.8 and 4.0 m at the upstream point of the wall. The modifications provided optimal hydraulic conditions, i.e. elimination of cross-waves and non-uniform flows. The Vedernikov and Montouri numbers showed that both original and modified series did not enter the area where the pulsating flow occurred. This indicated that both series were free from the pulsating flow.

Źródło:

Journal of Water and Land Development; 2023, 56; 51--57
1429-7426
2083-4535

Pojawia się w:

Journal of Water and Land Development

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 38.

Tytuł:

Practical aspects of the use of the sluice gate discharge equations to estimate the volumetric flow rate in the irrigation channels

Autorzy:

Kubrak, Elżbieta
Kubrak, Janusz

Powiązania:

https://bibliotekanauki.pl/articles/2174345.pdf

Data publikacji:

2022

Wydawca:

Instytut Technologiczno-Przyrodniczy

Tematy:

discharge coefficient
discharge calculation error
irrigation channel
laboratory model investigations
submerged sluice gate flow
volumetric flow rate

Opis:

The article presents the experimental results of the calibration of the typical check structure with sluice gates installed in a trapezoidal irrigation channel. Hydraulic experiments on sluice gate discharge capacity were performed on a model made in a 1:2 scale. It has been explained how the method of measuring the downstream water depth below the sluice gate in the check structures installed in a trapezoidal irrigation channels affects the measured depth values. On the basis of hydraulic measurements, regression relationships were developed for the discharge coefficients for submerged outflow through the sluice gate in two types of sluice gates installed in irrigation channels. The formulas allow to calculate the volumetric flow rate below the submerged sluice gate after determining the water depth upstream and below the sluice gate and the gate opening height. The differences in volumetric flow rates calculated from regression relationships and measured values do not exceed 10%, which confirms their practical suitability for calculating the discharge through a sluice gate mounted in a trapezoidal channel. The values of the discharge coefficients determined in the channels with rectangular cross-sections are not useful for the discharge coefficients of sluice gates check structures installed in trapezoidal channels. Nomograms and relationships for discharge coefficients of the analysed sluice gate were developed.

Źródło:

Journal of Water and Land Development; 2022, 55; 129--137
1429-7426
2083-4535

Pojawia się w:

Journal of Water and Land Development

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 39.

Tytuł:

A new approach for study the electrohydrodynamic oscillatory flow through a porous medium in a heating compliant channel

Autorzy:

Haroun, M. H.

Powiązania:

https://bibliotekanauki.pl/articles/1839817.pdf

Data publikacji:

2020

Wydawca:

Uniwersytet Zielonogórski. Oficyna Wydawnicza

Tematy:

przepływ oscylacyjny
elektrohydrodynamika
wymiana ciepła
oscillatory flow
electrohydrodynamics
porous medium
heat transfer
compliant channel

Opis:

The governing equations of an electrohydrodynamic oscillatory flow were simplified, using appropriate nondimensional quantities and the conversion relationships between fixed and moving frame coordinates. The obtained system of equations is solved analytically by using the regular perturbation method with a small wave number. In this study, modified non-dimensional quantities were used that made fluid pressure in the resulting equations dependent on both axial and vertical coordinates. The current study is more realistic and general than the previous studies in which the fluid pressure is considered functional only in the axial coordinate. A new approach enabled the author to find an analytical form of fluid pressure while previous studies have not been able to find it but have found only the pressure gradient. Analytical expressions for the stream function, electrical potential function and temperature distribution are obtained. The results show that the electrical potential function decreases by the increase of the Prandtl number, secondary wave amplitude ratio and width of the channel.

Źródło:

International Journal of Applied Mechanics and Engineering; 2020, 25, 3; 30-44
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: 40.

Tytuł:

Matematicheskoe opisanie povedenija zernovok podsolnechnika v vozdushnom potoke razdelitelnykh ustanovok
Mathematical description of the behavior of sunflower kernels in the air flow separation units

Autorzy:

Kolodijj, A.
Kjurchev, S.

Powiązania:

https://bibliotekanauki.pl/articles/77957.pdf

Data publikacji:

2015

Wydawca:

Komisja Motoryzacji i Energetyki Rolnictwa

Tematy:

mathematical description
sunflower
productivity
sowing material
grain separation
air flow
separation
aspiration channel

Źródło:

Motrol. Motoryzacja i Energetyka Rolnictwa; 2015, 17, 9
1730-8658

Pojawia się w:

Motrol. Motoryzacja i Energetyka Rolnictwa

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 41.

Tytuł:

Flow in a skewed compound open channel with trees on a flood plain

Autorzy:

Fukui, Y.
Urayama, T.
Takamizu, K.

Powiązania:

https://bibliotekanauki.pl/articles/241408.pdf

Data publikacji:

2003

Wydawca:

Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN

Tematy:

skewed compound open channel
trees on the flood plain
drag force
secondary flow

Opis:

In this research, the flow in a skewed compound channel with trees on the flood plain along the skewed part is studied. Three cases are assumed. Namely, 1) there are no trees on the flood plain along the main skewed part; 2) there are many trees on the flood plain set in order; and 3) there are many trees on the flood plain in disorder. In this research, 1) changes of water level and velocity in the channel; 2) the de-velopment of secondary flow as water flows downward; 3) the drag force due to the existence of trees; and 4) the changes of the river bed level in a movable bed condition are investigated. Numerical analyses using 2-D shallow water theory are also carried out to reproduce a flow in the skewed channel. As a result, the hydraulic quantities, for example water depth and the velocity cal-culated for a case setting trees in order and close together, are available in the river planning for a situation in which some of the trees were washed downstream. Such hydraulic quantities become severe for conditions in order and close to-gether in the flood. During the experiment using sand, channel beds are deformed by piling up and digging of sands or stones in various cases.

Źródło:

Archives of Hydro-Engineering and Environmental Mechanics; 2003, 50, 1; 3-19
1231-3726

Pojawia się w:

Archives of Hydro-Engineering and Environmental Mechanics

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 42.

Tytuł:

Experimental investigation of the two-phase flow regimes and pressure drop in horizontal mini-size rectangular test section

Autorzy:

Elazhary, A.
Soliman, H.

Powiązania:

https://bibliotekanauki.pl/articles/239912.pdf

Data publikacji:

2012

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

dwufazowy
minikanał
przepływ
spadek ciśnienia
flow regimes
mini channel
pressure drop
two-phase

Opis:

An experimental study was conducted in order to investigate two-phase flow regimes and fully developed pressure drop in a mini-size, horizontal rectangular channel. The test section was machined in the form of an impacting tee junction in an acrylic block (in order to facilitate visualization) with a rectangular cross-section of 1.87-mm height on 20-mm width on the inlet and outlet sides. Pressure drop measurement and flow regime identification were performed on all three sides of the junction. Air-water mixtures at 200 kPa (abs) and room temperature were used as the test fluids. Four flow regimes were identified visually: bubbly, plug, churn, and annular over the ranges of gas and liquid superficial velocities of 0.04 [ less than or equal to] JG [ less than or equal to] 10 m/s and 0.02 [ less than or equal to] JL [ less than or equal to] 0.7 m/s, respectively, and a flow regime map was developed. Accuracy of the pressure-measurement technique was validated with single-phase, laminar and turbulent, fully developed data. Two-phase experiments were conducted for eight different inlet conditions and various mass splits at the junction. Comparisons were conducted between the present data and former correlations for the fully developed two-phase pressure drop in rectangular channels with similar sizes. Wide deviations were found among these correlations, and the correlations that agreed best with the present data were identified.

Źródło:

Archives of Thermodynamics; 2012, 33, 2; 47-6
1231-0956
2083-6023

Pojawia się w:

Archives of Thermodynamics

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 43.

Tytuł:

Application of variation of the parameters method for micropolar flow in a porous channel

Autorzy:

Güngör, Osman
Arslantürk, Cihat

Powiązania:

https://bibliotekanauki.pl/articles/1839802.pdf

Data publikacji:

2020

Wydawca:

Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej

Tematy:

micropolar flow
porous channel
variation of parameters method
przepływ mikropolarny
metoda zmiany parametrów
kanał porowaty

Opis:

This work devoted to study the injective micropolar flow in a porous channel. The flow is driven by suction or injection on the channel walls, and the micropolar model is used to characterize the working fluid. The governing nonlinear partial differential equations are reduced to the nonlinear ordinary coupled differential equations by using Berman’s similarity transformation. These equations are solved for large mass transfer via variation of parameters method (VPM) which has been used effectively in the solution of nonlinear equations recently. This method has not previously been applied to a problem of micropolar flow. The results of the variation of parameters method are found to be in excellent agreement with the results of the Matlab bvp4c solver (NUM). With this validity, the effects of the some important parameters on the velocity and rotation profile of micropolar flow are discussed in detail. It can be seen that increases in the values N1 and N3 have different results in comparison with N2 increasing.

Źródło:

Journal of Applied Mathematics and Computational Mechanics; 2020, 19, 1; 17-29
2299-9965

Pojawia się w:

Journal of Applied Mathematics and Computational Mechanics

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 44.

Tytuł:

Application of variation of the parameters method for micropolar flow in a porous channel

Autorzy:

Güngör, Osman
Arslantürk, Cihat

Powiązania:

https://bibliotekanauki.pl/articles/122970.pdf

Data publikacji:

2020

Wydawca:

Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej

Tematy:

micropolar flow
porous channel
variation of parameters method
przepływ mikropolarny
metoda zmiany parametrów
kanał porowaty

Opis:

This work devoted to study the injective micropolar flow in a porous channel. The flow is driven by suction or injection on the channel walls, and the micropolar model is used to characterize the working fluid. The governing nonlinear partial differential equations are reduced to the nonlinear ordinary coupled differential equations by using Berman’s similarity transformation. These equations are solved for large mass transfer via variation of parameters method (VPM) which has been used effectively in the solution of nonlinear equations recently. This method has not previously been applied to a problem of micropolar flow. The results of the variation of parameters method are found to be in excellent agreement with the results of the Matlab bvp4c solver (NUM). With this validity, the effects of the some important parameters on the velocity and rotation profile of micropolar flow are discussed in detail. It can be seen that increases in the values N₁ and N₃ have different results in comparison with N₂ increasing.

Źródło:

Journal of Applied Mathematics and Computational Mechanics; 2020, 19, 1; 17-29
2299-9965

Pojawia się w:

Journal of Applied Mathematics and Computational Mechanics

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 45.

Tytuł:

Miejscowe straty ciśnienia przy przewężeniu kanału w warunkach opadającego w rurach pionowych przepływu mieszaniny gazowo-cieczowej
Local pressure drops of gas - liquid mixture downflowing at a channel contraction in vertical pipes

Autorzy:

Wiśniewska, J.
Witczak, S.

Powiązania:

https://bibliotekanauki.pl/articles/2070623.pdf

Data publikacji:

2009

Wydawca:

Stowarzyszenie Inżynierów i Techników Mechaników Polskich

Tematy:

przewężenia kanału
przepływ dwufazowy gaz-ciecz
struktury przepływu
straty ciśnienia
channel contraction
two-phase gas-liquid flow
flow patterns
pressure drops

Opis:

W pracy opisano wyniki badań dotyczących wpływu przewężenia pola przekroju rury pionowej na struktury i miejscowe opory przepływu mieszaniny dwufazowej gaz — ciecz. Wskazano na charakter zmian oporów przepływu oraz dokonano oceny przydatności znanych z literatury metod obliczania ich wartości.
The paper describes results of studies concerning an influence of cross-section contraction in a vertical pipe on flow patterns and local pressure drop in gas - liquid two-phase flow. A change in pressure drop values was described and the applicability evaluation of methods known from literature for pressure drop calculations were verified.

Źródło:

Inżynieria i Aparatura Chemiczna; 2009, 6; 192-193
0368-0827

Pojawia się w:

Inżynieria i Aparatura Chemiczna

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 46.

Tytuł:

Urban environment influence on distribution part of logistics systems

Autorzy:

Galkin, A.

Powiązania:

https://bibliotekanauki.pl/articles/224141.pdf

Data publikacji:

2017

Wydawca:

Polska Akademia Nauk. Czytelnia Czasopism PAN

Tematy:

logistics channel
material flow
transport planning cities
automobilization level
logistyka
przepływ materiału
planowanie transportu
poziom motoryzacji

Opis:

The irregularities of evolutionary development, continuous improvement of environmental component into transport and raise many unsolved problem in the fields of transport in logistics systems and material flows management. The city parameters analyses had highlighted connections with transport services technology. Also the distribution stage of the logistic chain, which consists of following market participants: incoming material flow, retailers and Transportation Company (carrier) in different cities has been considered. Transportation service is made by road transport. The paper compares results of transportation servicing in different cities and logistic chains with same technology. As performance indicator net present value has been used. Existing criteria for evaluating the effectiveness of distribution of material flows does not sufficiently take into account the time value of money and possible options for investment, so when estimating the performance of servicing of business investment indicators should be used. Paper should elucidate the impact of cities on the transport service efficacy. Practical suggestions on logistics system functioning and transportation service of retailers in urban area have been proposed. Obtained results discovered overall impact of city’s parameters (density of streets and roads network’ irregularity factor; automobilizationlevel; urban square; scheme of road network; city radius) on logistics according to model which include more than 50 parameters and allows finding regularities of changing logistics efficiency on them.

Źródło:

Archives of Transport; 2017, 42, 2; 7-23
0866-9546
2300-8830

Pojawia się w:

Archives of Transport

Dostawca treści:

Biblioteka Nauki

/5

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Skocz do pozycji: 47.

Tytuł:

Generator minipęcherzy w minikanale
Mini bubbles generator in mini channel

Autorzy:

Górski, G.
Mosdorf, R.

Powiązania:

https://bibliotekanauki.pl/articles/1366463.pdf

Data publikacji:

2015

Wydawca:

Centralny Ośrodek Badawczo-Rozwojowy Aparatury Badawczej i Dydaktycznej, COBRABiD

Tematy:

minikanał
przepływ dwufazowy
analiza nieliniowa
generator minipęcherzy
mini channel
two-phase flow
nonlinear analysis
mini bubble generator

Opis:

W pracy przeprowadzono analizę porównawczą rozwiązań konstrukcyjnych mieszalników fazy ciekłej z fazą gazową. Pokazano, że w zaproponowanych rozwiązaniach trudno jest sterować ilością pęcherzy w podłączonym do nich minikanale, a tym samym niemożliwe jest uzyskanie wszystkich rodzajów przepływu dwufazowego. W pracy przedstawiono własną koncepcję generatora mini i mikropęcherzy, który pozwala na formowanie oczekiwanej struktury przepływu dwufazowego w minikanale. Generator wykorzystano do wytworzenia minipęcherzy w minikanale. Urządzenie testowano dla czterech różnych przewodów o średnicach wewnętrznych: 1, 2, 4, 5 mm. We wszystkich przypadkach generator tworzył pęcherze o różnych średnicach.
The gas-liquid mixers construction were compared in this paper. New conception of mini and micro bubbles generator is presented. The generator is used to form of mini bubbles in mini channel. The testing was conducted in tubes with the internal diameters of 1, 2, 4 and 5 mm. The different diameters of bubbles were formed for each generator constructions.

Źródło:

Aparatura Badawcza i Dydaktyczna; 2015, 20, 2; 146-156
2392-1765

Pojawia się w:

Aparatura Badawcza i Dydaktyczna

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 48.

Tytuł:

Rheodynamics non-viscous medium in long (cylindrical) pipes: using the Ostwald-De Ville model

Autorzy:

Brovatets, Oleksandr
Chоvniuk, Yuiry
Moskvitina, Anna

Powiązania:

https://bibliotekanauki.pl/articles/1833884.pdf

Data publikacji:

2020

Wydawca:

Polska Akademia Nauk. Oddział w Lublinie PAN

Tematy:

rheodynamics
nonlinear viscous medium
long channels
round channel sections
rectangular channel sections
Ostwald-de Waele model
heat transfer
non-isothermal flow
heat exchangers
polyethylene glycol
ethylene glycol

Opis:

While heating the soil in greenhouses, ground heat exchangers are used, as well as when accumulating heat in soil massifs for further use of heat by heat pumps, or when accumulating heat from solar collectors in heat accumulators. In such cases, a coolant moves in the heat exchangers, which will not freeze or boil, most often these are solutions polyethylene/ethylene glycol, which belong to nonlinear viscous fluids. In this work, the nonisothermal motion of a nonlinear-viscous fluid (within the framework of the Ostwald - de Ville model) in a flat channel with a given heat flow on the wall is investigated. A characteristic feature of the flow of such media is their high thermal sensitivity due to phase and structural transformations. Therefore, with a change in temperature, there is a sharp change in rheological properties. For a number of materials, for example, for polyethylene glycol (ethylene glycol) mixtures, for glycerol solutions, these changes can occur in a fairly narrow temperature range. The flow in a channel is considered, the length of which is much greater than the length of the hydrodynamic and thermal initial sections. The case is investigated when the temperature changes along the channel. Channels of arbitrary cross-section (and, in particular, rectangular and circular) are considered. The situation is analyzed when the temperature changes along the channel, and this change is rather weak in relation to the temperature change along the channel walls (in the transverse direction, that is, in the plane of symmetry). To describe the state of the system, the so-called state diagram (dependence of the temperature on the axis of symmetry of the channel on the heat flux).

Źródło:

ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes; 2020, 9, 2; 19--22
2084-5715

Pojawia się w:

ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 49.

Tytuł:

Modeling the hydrodynamic interactions between the river morphology and navigation channel operations

Autorzy:

Badawy, Neveen Abdel-Mageed
El-Hazek, Alaa N.
Elsersawy, Hossam Mohamed
Mohammed, Ebtesam Rezk

Powiązania:

https://bibliotekanauki.pl/articles/2048502.pdf

Data publikacji:

2021

Wydawca:

Instytut Technologiczno-Przyrodniczy

Tematy:

adaptive hydraulics (ADH) model
draw down
navigation channel
the Nile River
restricted waterway
return flow
shear stress

Opis:

The Nile River is the main route for inland navigation in Egypt. The vessels navigating through inland waterways generate complex physical forces that need to be studied extensively. Quantifying the effects of vessels sailing along a waterway is a complex problem because the river flow is unsteady and the river bathymetry is irregular. This paper aims to investigate the hydrodynamic effects resulting from the movement of vessels such as return currents around the vessel, the draw down of the water surface, under keel clearance, and the shear stress induced by vessels operating in the Nile River. Modeling such effects has been performed by applied the two-dimensional ADH (adaptive hydraulics) model to a river reach for different navigation channel operation scenarios. The obtained results show that the draw down heights, the water fluctuation, and the shear stress magnitude are larger when the river cross sectionals are narrow and the shallow water depths. These river sections are considered more disposed to bed erosion and it is morphologically unsafe. The section having the narrowest width and the lowest depth was associated with the largest drawdown percentages of 98.3% and 87.3% in one-way and two-way scenarios. While the section having the widest width and the largest depth was associated with the least drawdown percentages of 48.5% and 51.9% in one-way and two-way scenarios. The section having the narrowest width and the lowest depth was associated with the largest fluctuations of 22.0 cm and 41.9 cm in one-way and two-way scenarios. While the section having the widest width and the largest depth was associated with the least fluctuations of 0.6 cm and 1.8 cm in one-way and two-way scenarios. The section having the narrowest width and the lowest depth was the worst section for under keel clearance of 5.0 cm and 33.3 cm in one-way and two-way scenarios. While the section having the widest width and the largest depth was the best section, where its clearance values were 183.2 cm and 155.0 cm in one-way and two-way scenarios. It is concluded that a numerical model is a valuable tool for predicting and quantifying the hydrodynamic effects of vessels moving through a two-dimensional flow field and can be used to evaluate different scenarios that are difficult to measure in the field or a physical model. Also, it provides visualization products that help us understand the complicated forces produced by vessels moving in a navigation channel.

Źródło:

Journal of Water and Land Development; 2021, 51; 1-10
1429-7426
2083-4535

Pojawia się w:

Journal of Water and Land Development

Dostawca treści:

Biblioteka Nauki

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Skocz do pozycji: 50.

Tytuł:

Zastosowanie metody elementów brzegowych do wyznaczania jednokierunkowego przepływu w przewodach prostoosiowych o dowolnym kształcie przekroju poprzecznego
Implementation of the boundary element method for the solution of unidirectional flow through straight pipes of arbitrary cross-section shapes

Autorzy:

Teleszewski, T.
Sorko, S. A.

Powiązania:

https://bibliotekanauki.pl/articles/386637.pdf

Data publikacji:

2011

Wydawca:

Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej

Tematy:

przewody
kanały
przepływ cieczy
układy przepływowe
metoda elementów brzegowych
pipe
channel
flow of fluid
boundary element method

Opis:

Przedmiotem opracowania jest aplikacja metody elementów brzegowych do wyznaczania przepływu w prostoosiowych przewodach i kanałach o dowolnym kształcie przekroju poprzecznego całkowicie wypełnionych cieczą. Laminarny, jednokierunkowy przepływ cieczy lepkiej opisany równaniem Stokesa jest zadowalającym modelem do opisu licznej klasy przepływów w układach przepływowych maszyn i urządzeń. W pracy przedstawiono rozwiązanie zagadnienia przepływu jednokierunkowego cieczy newtonowskiej ograniczonego walcową powierzchnią o dowolnym kształcie przekroju poprzecznego w sformułowaniu brzegowych równań całkowych. Przedstawiono rezultaty wyników obliczeń pola prędkości w przepływie jednokierunkowym dla wybranych kształtów przekroju poprzecznego przewodów i dokonano porównania rozwiązań numerycznych z dostępnymi w literaturze rozwiązaniami analitycznymi wykazując zadowalającą dokładność i skuteczność metody brzegowych równań całkowych do rozwiązywania tej grupy zagadnień przepływowych w zastosowaniach technicznych.
The subject of the presented elaboration is the applica- tion of the boundary integral method to calculating of the pressure driven unidirectional flow in pipes and channels of arbitrary shape of the cross-section. The laminar unidirectional flow of viscous fluid described by Stokes equation is a satisfactory model to the description of the numerous flows in machines and engineering devices. In the paper is presented the solution of the problem of the flow of Newtonian liquid limited by the cylindrical surface about the arbitrary shape of the cross-section in the expression of boundary integral equations. The results of calculations the velocity field of unidirectional flow through pipes and straight closed ducts of the selected shapes of the cross-section with comparisons of numeric solutions with accessible in the literature with analytic solutions showing the satisfactory exactitude and the efficiency the method boundary integral equations to the solution this class of problems of flow in technical uses.

Źródło:

Acta Mechanica et Automatica; 2011, 5, 3; 124-131
1898-4088
2300-5319

Pojawia się w:

Acta Mechanica et Automatica

Dostawca treści:

Biblioteka Nauki

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