Wyniki wyszukiwania - Biblioteka Nauki

1

MHD flow and heat transfer of a Bingham fluid in an eccentric annulus with the Hall effect

100%

Sayed-Ahmed M. E. , Attia H. A.

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2007

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tom Vol. 14, No. 1

25-42

EN

The steady laminar flow and heat transfer of an incompressible, electrically conducting, non-Newtonian Bingham fluid in an eccentric annulus are studied in the presence of an external uniform magnetic field. The inner cylinder is subject to a constant heat flux while the outer cylinder is adiabatic and, the viscous and Joule dissipations are taken into consideration. The governing momentum and energy equations are solved numerically using the finite difference approximations. The velocity, the temperature, the volumetric flow rate and the average Nusselt number are computed for various values of the physical parameters.

2

MHD nonlinear flow and heat transfer over a stretching porous surface of constant heat flux

86%

Anjali Devi S. P. , Ganga B.

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2008

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tom Vol. 15, No. 1

15-22

EN

MHD nonlinear steady flow and heat transfer over a porous surface stretching with a power-law velocity and of constant heat flux is investigated. The governing nonlinear partial differential equations are reduced to nonlinear ordinary differential equations by using similarity transformation. As the presented solution method requires the magnetic field to vary in space in a specific manner, a special form for the variable magnetic field is chosen. Resulting equations are numerically solved by Runge–Kutta shooting method. Values of skin-friction and rate of heat transfer are obtained. The effect of magnetic field, stretching parameter, magnetic interaction parameter, suction parameter and Prandtl number over a flow field and other physical quantities have been discussed in detail.

3

MHD fluctuating free convective flow with radiation embedded in porous medium having variable permeability and heat source/sink

72%

Sharma B. , Agarwal M. , Chaudhary R. C.

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2006

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tom Vol. 47, no 1

47-58

EN

The study of free convective two-dimensional unsteady flow with radiation through a porous medium of variable permeability and transverse magnetic field in presence of a heat source/sink, bounded by an infinite vertical porous plate with uniform suction, has been made. The permeability of a porous medium fluctuates with time about a constant mean. Approximate solutions for velocity, temperature and skin friction are obtained and the effects of heat source/sink, radiation, variable permeability, Prandtl number and magnetic field parameter on velocity, temperature and skin friction are shown and discussed with the help of graphs and a table.

4

Optymalizacja parametrów napędu magnetohydrodynamicznego z kanałem o przekroju eliptycznym

72%

Mąka M.

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2005

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tom R. 81, nr 7-8

86-90

PL

W artykule rozpatrywany jest problem optymalizacji parametrów silników magnetohydrodynamicznych z kanałem o przekroju eliptycznym. Analizowane jest zagadnienie doboru parametrów geometrycznych kanału i warunków zasilania silnika pod kątem uzyskania maksymalnej sprawności. Ponadto przedstawiono analizę możliwości doboru wymiarów geometrycznych napędu i określonych warunków zasilania w celu uzyskania jak najwyższej gęstości mocy wyjściowej.

EN

This article discusses a problem of optimisation of some parameters of magnetohydrodynamic engines with an elliptical cross-section channel. The channel geometric parameters, engine supply conditions and magnetic circuit configuration are analysed in order to receive maximum efficiency. Besides, analyzed are the propulsion geometric dimensions and supply conditions with the aim of maximizing the output power density.

5

MHD free convection heat and mass transfer in a doubly stratified Darcy porous medium considering Soret and Dufour effects with viscous dissipation

72%

Kishan N. , Reddy M. C. K. , Govardhan K.

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2009

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tom Vol. 14, no 3

733-745

EN

Numerical studies are performed to examine the Soret, Dufour and viscous dissipation effects on steady MHD, free convection heat and mass transfer from a vertical surface in a doubly stratified Darcy porous medium. The non-linear partial differential equations, governing the problem under consideration, have been transformed by a similarity transformation into a system of ordinary differential equations, which is solved numerically by using the implicit finite difference scheme. The effects of various parameters on the flow field have been examined. The results for the wall temperature and concentration obtained are presented for various values of the parameters Le, N, M, Ec, Sr, Df, [...].

6

Switching arc simulation

72%

Tarczyński W. , Daszkiewicz T.

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2012

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tom R. 88, nr 7b

60-64

EN

This paper is a general review of research studies with computer simulations of electric arc in electric circuit breakers, taking into account the magnetohydrodynamic model of electric arc and there are described the formation and the decay of discharge channels in alternating current arcs of Imax = 500 A in atmospheric pressure and in a model system, designed with the ANSYS-Fluent software. Diagrams of mass velocity, temperature and current density distributions are presented. An ultra-fast digital camera (20 000 frames/s) was used in the experimental studies.

PL

W artykule przedstawiono przegląd badań dotyczących komputerowej symulacji łuku łączeniowego w wyłącznikach, przy wykorzystaniu magnetohydrodynamicznego opisu modelu łuku. Opisano też powstawanie nowych i zanikania starych kanałów wyładowczych w łukach prądu przemiennego Imax = 500 A, palących się w powietrzu (ciśnienie atmosferyczne), w czasie symulacji palenia się łuku. Podano wykresy rozkładów prędkości masy, temperatury i gęstości prądu. W eksperymentach zastosowano ultra-szybką kamerę filmową (20 000 k/s).

7

The analysis of the suction/injection on the MHD Maxwell fluid past a stretching plate in the presence of nanoparticles by Lie group method

71%

Cao L. , Si X. , Zheng L. , Pang H.

Open Physics

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2015

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tom 13

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nr 1

EN

In this paper, the magnetohydrodynamic (MHD) Maxwell fluid past a stretching plate with suction/ injection in the presence of nanoparticles is investigated. The Lie symmetry group transformations are used to convert the boundary layer equations into non-linear ordinary differential equations. The dimensionless governing equations are solved numerically using Bvp4c with MATLAB, which is a collocation method equivalent to the fourth order mono-implicit Runge-Kutta method. The effects of some physical parameters, such as the elastic parameter K, the Hartmann number M, the Prandtl number Pr, the Brownian motion Nb, the thermophoresis parameter Nt and the Lewis number Le, on the velocity, temperature and nanoparticle fraction are studied numerically especially when suction and injection at the sheet are considered.

8

Unsteady MHD Couette Flow with Heat Transfer in the Presence of Uniform Suction and Injection

71%

Attia H. A.

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2008

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tom Vol. 12, nr 2

165-170

EN

The unsteady Couette flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to a constant pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the magnetic field and the uniform suction and injection on both the velocity and temperature distributions is examined.

9

Transient free convection MHD flow between two long vertical parallel plates with constant temperature and mass diffusion

61%

Rajput U. S. , Sahu P. K.

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tom Vol. 17, no. 2

459-469

EN

A transient free convection flow between two long vertical parallel plates with constant temperature and mass diffusion was studied by Narahari Marneni (2008). In the present paper, we investigate the effects of MHD on transient free convection flow of an incompressible viscous electrically conducting fluid between two infinite vertical parallel plates with constant temperature and mass diffusion, under the assumption that the induced magnetic field is negligible. The Laplace transform method is used to find the solutions for the velocity, temperature and concentration profiles. The velocity, temperature and concentration profiles are studied for different parameters like the Prandtl number, Schmidt number, magnetic parameter, buoyancy ratio parameter and time. The values of the skin-friction and volume flux for different parameters are tabulated.

10

Exact solution of an oscillatory MHD flow in a channel filled with porous medium

61%

Singh K. D.

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2011

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tom Vol. 16, no 1

277-283

EN

An exact solution of an oscillatory MHD flow of a viscous, incompressible and electrically conducting fluid in an infinite horizontal channel is presented. The channel is filled with a porous medium and a magnetic field is applied perpendicular to the plates of the channel. During the analysis it is found that the mathematical formulation and the solution obtained of the problem by Makinde and Mhone (2005) are both wrong. Equations (2.1) to (2.4) do not govern the flow problem shown geometrically in their Fig.1. This important flow problem is again formulated mathematically in the present paper and a fresh and a correct closed form analytical solution is obtained. The validity and correctness of the present solution is verified by the limiting case for H=s=0. In this case of oscillatory flow in the absence of a magnetic field and through ordinary medium the solution reduces to the well known result obtained by Schlichting and Gersten (2001). The results are discussed in detail with the help of graphs for the variations of different flow parameters.

11

Hartmann two-fluid Poiseuille-Couette flow in an inclined channel

61%

Umavathi J. C. , Sridhar K. S. R.

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2009

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tom Vol. 14, no 2

539-557

EN

A numerical and analytical study of a two fluid magnetohydrodynamic Poiseuille-Couette flow in an inclined channel is investigated. The fluids in both the regions are incompressible, electrically conducting and the transport properties are assumed to be constant. The channel walls are assumed to be electrically insulating. Separate solutions for each fluid are obtained and these solutions are matched at the interface using suitable matching conditions. The governing equations of motion are solved analytically and are valid for small Eckert numbers and numerically valid for large . Solutions for large show a marked change on the velocity and temperature profiles. The results are presented graphically for various Hartmann number, Grashof number, angle of inclination and also for various ratios. It is found that the flow can be controlled effectively by a suitable choice of values of ratios of electrical conductivities, widths, viscosities and thermal conductivities.

12

The effect of suction on magnetohydrodynamic forced flow of a viscous electrically conducting fluid through a porous medium induced by a rotating disk

61%

Sharma B. K. , Jha A. K. , Chaudhary R. C.

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tom Vol. 17, no. 4

1297-1308

EN

The present paper investigates the steady MHD forced flow of an incompressible viscous electrically conducting fluid, due to an infinite rotating disk bounded by a porous medium. A uniform suction is applied on the upper disk. It is assumed that the flow between the disk and the porous medium is governed by Navier-Stokes equations and that in the porous medium by Brinkman equations. Flows in the two regions are matched at the interface by assuming that the velocity and stress components are continuous at it. At the interface (porous medium-clear fluid boundary), a modified set of boundary conditions suggested by Ochao-Tapia and Whittaker is applied. Assuming constant suction at the disk surface, analytical expressions for the velocity and shearing stress are calculated and effects of various parameters upon them are examined.

13

Wpływ stałego pola magnetycznego na elektropolimeryzację aniliny

58%

Zieliński M.

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2008

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tom Vol. 61, nr 6

264-267

PL

Z uwagi na łatwość elektrochemicznego otrzymywania polianiliny, a także możliwość pełnej kontroli przebiegu procesu, warto było zbadać jego charakterystykę w stałym polu magnetycznym (s.p.m.). Zastosowano do tego celu metodę chronowoltamperometrii cyklicznej. Procesy polimeryzacji aniliny prowadzono na elektrodach platynowych, płytkowych, nieizolowanych (A) i izolowanych z dwóch różnych stron teflonem, o powierzchniach skierowanych równolegle do linii sił s.p.m. Badania elektrochemicznego otrzymywania polianiliny w s.p.m. pozwoliły stwierdzić, że na wielkość prądu badanego procesu wpływają następujące czynniki: 1) wielkość wektora indukcji magnetycznej B, 2) pozycja płaszczyzny elektrody w stosunku do wektora B, 3) typ elektrody (izolowana jednostronnie, bądź nie). Wpływ na wielkość oddziaływania s.p.m. na procesy elektrochemiczne polimeryzacji miały również właściwości magnetyczne (np. paramagnetyczne, diamagnetyczne) cząstek biorących udział w reakcji elektrochemicznej a także ich ładunek (+/-). Na podstawie wyników eksperymentalnych zaproponowano mechanizm wpływu s.p.m. na badane reakcje elektrochemiczne. Mechanizm ten oparto między innymi na powstawaniu efektu magnetohydrodynamicznego (MHD), który powoduje zmianę szybkości transportu reagujących substancji do elektrody, magnetohydrodynamicznym ruchu elektrolitu i zmianie kinetyki procesów elektrodowych. Dla badanego procesu, zmiany stałych szybkości reakcji elektrochemicznych (ks) na skutek działania zewnętrznego s.p.m. wynosiły maksymalnie do ok. 30%.

EN

Due to the simplicity of the electropolymerization of aniline, as well as the possibility of a thorough control of this process, it is worthwhile to analyse its characteristics in the constant magnetic field (c.m.f.). The method of cyclic voltammetry has been applied. Electropolymerization of aniline was done on the platinum electrodes, non isolated, and teflon isolated ones on one side, with the active areas oriented parallel to the c.m.f. force lines. It was found that there are the following factors that affect the current of the process under investigation: 1) the magnetic induction vector B, 2) the direction of the electrode surface versus vector B direction, 3) the electrode types (one side isolated or non isolated). The magnetic properties of the reacting molecules (eg. paramagnetic, diamagnetic) and their charges (+/-) have also influenced on the extent of action of c.m.f. on electropolymerization process. The mechanism of c.m.f. action on the studied electrochemical reactions was proposed. It was based on appearance of magnetohydrodynamic effect (MHD), which manifests transport velocity change of the reacting species to the electrode, magnetohydrodynamicaly movement of the electrolyte, and electrode processes kinetics changes. The maximum changes of constant rates of aniline electropolymerization reactions, resulted from external c.m.f., were reaching up to about 30%.

14

Magnetohydrodynamic free convection heat and mass transfer over an oscillating plate with radiation absorption - an exact solution

51%

Chaudhary R. C. , Jain P.

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2008

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tom Vol. 13, no 4

903-921

EN

The problem of magnetohydrodynamic free-convection flow past an infinite vertical oscillating plate in the presence of chemical species concentration and thermal radiation effects has been solved. The plate temperature increases linearly with time and the fluid considered here is a gray, absorbing-emitting radiation but a non-scattering medium. The governing equations are non-dimensionalized and their solutions are obtained in a closed form using the Laplace-transform technique. A parametric study is performed to illustrate the influence of the radiation parameter, magnetic parameter, thermal Grashof number, mass Grashof number, time, Schmidt number and frequency of oscillations on the velocity, temperature and concentration profiles. The variation of the dimensionless skin-friction coefficient, wall heat transfer and the Sherwood number for different values of the parameters appearing in their expression is also shown with the help of figures.

15

MHD natural convection heat and mass transfer in a micropolar fluid from radiate vertical porous surfaces with chemical reaction

51%

Modather M. , Abdou M. , El-Kabeir S. M.

|

2007

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tom Vol. 12, no 3

745-765

EN

The effect of a chemical reaction on the free convection flow of a viscous incompressible conductive micropolar fluid from a radiative vertical porous plate with a uniform surface temperature, uniform rate of suction or injection and uniform magnetic field is investigated. The Rosseland diffusion approximation is used to describe the radiative heat flux in the energy equation. As the micropolar parameter increases the temperature, concentration and microrotation increase while the velocity decreases for the suction and injection case and increasing the chemie al reaction parameter decreases the velocity, concentration and microrotation for the suction and injection case while the temperature increases with the increasing of the chemical reaction parameter.

16

Three - dimensional MHD free - convection flow past an infinite vertical porous plate with gravity modulation

51%

Saini B. S. , Rajvanshi S. C.

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2011

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tom Vol. 16, no 4

1093-1107

EN

In the present study, the effect of a fluctuating gravitational field on a three - dimensional MHD free - convection flow past a vertical porous plate with transversally varying suction velocity is investigated. A constant heat flux is prescribed on the plate. It is assumed that the gravity modulation is given by […]. The transformed equations are solved by the perturbation technique. The effect of various physical parameters on the fluid velocity and temperature are computed numerically and discussed through graphs.

17

Heat transfer in MHD viscoelastic boundary layer flow over an exponential stretching sheet

51%

Nandeppanavar M. M. , Subhas Abel M. , Ravi S. , Jyoti H.

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2011

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tom Vol. 16, no 2

455-474

EN

An analysis has been carried out to study the steady viscoelastic hydromagnetic flow and heat transfer in a visco-elastic liquid flow over an exponentially stretching sheet with consideration of viscous dissipation. A zeroth order analytical local similar solution of the highly non-linear stream function equation and confluent hypergeometric solution of the heat transfer equation is obtained by converting the governing partial differential equation to ordinary differential equation by similarity transformations. The accuracy of the analytical solution for the stream function is verified by a numerical solution obtained by employing the Runge-Kutta fourth order method with shooting. The two following cases of surface conditions are studied, namely (1) prescribed exponential order surface temperature (PEST Case) and (2) prescribed exponential order boundary heat flux (PEHF Case). The effect of various parameters arising in the flow on momentum and heat transfer characteristics are presented graphically and the numerical results of wall temperature gradient (in PEST Case ) and wall temperature (PEHF Case ) are tabulated and compared with previous results.

18

Buoyancy and Soret effect on unsteady MHD mixed convective slip flow in a permeable vertical plate

51%

Rashi Kumar B. , Sivaraj R.

|

tom Vol. 17, no. 1

179-190

EN

This paper is focused on the study of heat and mass transfer in the unsteady MHD mixed convective flow of a viscous incompressible fluid bounded by a permeable vertical plate subject to the influence of buoyancy, viscous dissipation, ohmic heating and the Soret effect embedded with slip condition at the boundary layer. In order to obtain a better insight into this problem, we make use of the perturbation method. The results for velocity, temperature, concentration, skin friction, the Nusselt number as well as the Sherwood number are examined analytically and the effects of various significant parameters entering into this problem are displayed graphically.

19

Heat and mass transfer effects on an oscillatory mhd convective flow through porous medium in a rotating porous channel with heat radiation

51%

Singh K. D. , Pathak R.

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tom Vol. 17, no. 4

1309-1326

EN

An oscillatory MHD convective and mass transfer flow of an electrically conducting, viscous, incompressible fluid in a rotating porous channel filled with a porous medium has been analyzed. Effects of radiation and chemical reaction are also considered. The two porous plates are subjected to a constant injection and suction. It is considered that the influence of the uniform magnetic field acts normal to the flow. The entire system rotates about an axis normal to the planes of the plates with uniform angular velocity [...]. Expressions for velocity, temperature, concentration, and amplitude and phase angle of skin-friction, the Nusselt number and Sherwood number are obtained. The results obtained for velocity are discussed for small (...) and large (...) rotation of the channel with the help of graphs.