Wyniki wyszukiwania - Biblioteka Nauki

1

Hiemenz flow of a micropolar fluid in hydromagnetics

100%

Mohammadein A. A. , El Kabeir S. M. , El-Hakiem M. A. , Gorla R. S. R.

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1998

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tom Vol. 3, no 3

367-376

EN

A boundary layer analysis has been presented for Hiemenz flow in hydromagnetics of a micropolar incompressible, viscous, electrically conducting fluid impinging normal to a plane in the presence of a transverse magnetic field. Numerical solutions are given for the governing momentum and angular momentum equations. An approximate solution is given which is simple and yet sufficiently accurate for the entire range of values of Harman number investigated. A discussion has been provided for the effect micropolar parameters on Hiemenz flow in hydromagnetics.

2

Flow of a Vočadlo fluid in a slot between rotating surfaces of revolution

100%

Walicki E. , Walicka A.

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1998

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tom Vol. 3, no 2

339-358

EN

This paper contains formulae which define such parameters of the steady laminar flow of a Vočadlo fluid between rotating surfaces of revolution as the velocity components 'TETA'x, 'TETA'teta, 'TETA'y and pressure p. The quasi-linearized equations of motion of the Vočadlo fluid flow for axial symmetry in the intrinsic curvilinear coordinate system x, 'teta', y are used. The obtained solutions to the equations of motion have been illustrated by an example of flow through the slot of constant thickness between rotating disks and between rotating spherical surfaces.

3

Computer simulation of fluid flow and heat transfer in strip casting of aluminum alloys

100%

Kuznetsov A. V.

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1998

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tom Vol. 3, no 3

479-490

EN

In this study, results of numerical analysis of the continuous casting process aimed for a production of thin aluminum-copper strips are reported. A characteristic feature of the continuous casting process considered in this paper is a strong forced convection of liquid alloy caused by a changing height of a free surface. Computations are performed for Al-4.5 wt pct Cu alloy. In this investigation, heat transfer process is coupled with the fluid flow which occurs in the liquid metal and in the mushy zone. It is shown that there is an essential forced convection flow in the upper part of mushy zone between the position where the liquidus line reaches the free surface and the position where the height of the free surface reaches its maximum. This flow can cause a destruction of the dendritic structure which in its turn can be one of the reasons for instability of the process.

4

Effects of the side walls in generalized Couette flow

100%

Erdogan M. E.

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1998

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tom Vol. 3, no 2

271-286

EN

The effects of the side walls on the flow of an incompressible viscous fluid in a conduit of rectangular cross-section by the combined effect of the velocity of the top wall and a constant pressure gradient along the conduit are considered. For this purpose, four different flow conditions are used. In the first case, a separation occurs at the bottom wall. In the second case, the volume flux is zero. In the third case, a separation occurs at the top wall. In the fourth case, the flow is set up by the motion of the top wall in the absence of the pressure gradient. Furthermore, the effect of the side walls in a channel of rectangular cross-section is discussed.

5

Variable viscosity effects on natural convection in micropolar fluid at an axisymetric stagnation point

100%

Mohammadein A. A. , El-Kabeir S. M. , Gorla R. S. R.

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1998

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tom Vol. 3, no 4

539-552

EN

A three-dimensional boundary layer solution is presented for the natural convection in a micropolar fluid in the vicinity of an axisymmetric stagnation point on heated vertical surfaces. The effects of variable viscosity are included. The governing equations for the velocity, microrotation and temperature fields are solved numerically.

6

Unsteady flow of a viscous fluid due to an oscillating plane wall

100%

Erdogan M. E.

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1998

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tom Vol. 3, no 3

465-478

EN

The flow of a viscous fluid produced by a plane boundary moving in its own plane with a sinusoidal variation of velocity is considered. An analytical solution describing the flow at small and large times after the start of the boundary is obtained by the Laplace transform method. The solution confirms that the intuitive solution known in the literature, which for a long time steady periodic oscillation is set up with the same frequency as the velocity of the plane boundary, is correct. The solution gives not only the steady solution but also the transient solution. The time required to attain steady flow depends on the initial conditions. The time required for the cosine oscillation of the boundary is one-half cycle and it is a full cycle for the sine oscillation of the boundary. It is shown that the time required to attain the steady flow can also be obtained by the variation of the shear stress at the wall with time.

7

Effects of a transverse magnetic field on natural convection with temperature dependent viscosity in micropolar fluids

100%

El-Hakiem M.

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1998

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tom Vol. 3, no 2

287-304

EN

A regular parameter perturbation analysis is presented to study the effect of uniform transverse magnetic field with temperature dependent viscosity in micropolar fluids. Four different vertical flows have been analyzed: these adjacent to an isothermal surface, uniform heat flux surface, a plane plume and wall plume. Viscous dissipation, motion pressure and volumetric energy source effects are neglected. The absolute viscosity 'mi' is taken to be variable in the force momentum balance while the fluid volumetric coefficient of thermal expansion, 'beta', specific heat, Cp and thermal conductivity, k, are assumed to be constant. Numerical solutions are obtained for different values of the magnetic field, material parameters and micropolar parameters.

8

Radiation interaction on forced and free convection across a horizontal cylinder

100%

Hossain M. A. , Kutubuddin M. , Takhar H. S.

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1999

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tom Vol. 4, no 2

219-235

EN

An analysis is performed to study the flow and heat transfer characteristics of laminar combined forced and free convection, with the effects of radiation, of a viscous incompressible and optically dense fluid from a horizontal cylinder. The transformed convection equations of non-similar boundary layers obtained for both the forced convection flow and the natural convection flow dominated regimes are solved by the implicit finite difference method. Numerical results are obtained for different physical parameters, such as the Rosseland parameter, Rd and the surface temperature parameter, __ , for fluids having the Prandtl number of 0.7. Results are presented in terms of local skin-friction and the local Nusselt number against the angular displacement, _ ,as well as the buoyancy parameter, __ . It is observed that both the local shear and the Nusselt number increase due to an increase in the values of Rd and __ , in the entire pure forced to pure free convection regimes.

9

Lubrication of a slider bearing with a special third grade fluid

100%

Yurusoy M. , Pakdemirli M.

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1999

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tom Vol. 4, no 4

759-772

EN

Lubrication of a slider bearing with a non-Newtonian fluid is considered. The fluid is a third grade fluid. Under the assumptions of the order of magnitudes of the variables, it is seen that only viscous and third grade terms are effective, whereas second grade terms and inertia terms are negligible. Choosing third grade effects to be smaller than the viscous effects, a perturbation solution is constructed. The velocity profile and the pressure distribution in the bearing is calculated approximately.

10

Tests on a new method for numerical solution to the Navier-Stokes equations*. Part I: plane unsteady flow in finite, rectangular domains

100%

Klonowska M. E. , Kołodziejczyk M.

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1999

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tom Vol. 4, no 2

311-339

EN

The paper deals with a new method (Prosnak and Kosma, 1991) for the determination of unsteady, plane flows of viscous incompressible fluids. The characteristic feature of the method consists in elimination of pressure from the system of the Navier-Stokes equations governing the flow - in such a manner that the order of the resulting system is not increased in comparison with the original one. Furthermore, the mathematical problem posed for the resulting system is reduced in the frame of the method to an initial problem for a system of first order ordinary differential equations, wherein time represents the only independent variable. The nonlinearities of the Navier-Stokes equations do not cause any difficulties by virtue of such an approach. In this paper, the method has been applied to flows in plane, finite rectangular domains, and domains composed of rectangles. Numerical solutions to such problems are presented in the paper in graphical form, and some conclusions are drawn concerning the results as well as the method.

11

Heat transfer from a stretching surface in a micropolar fluid

100%

El-Hakiem M. A. , Mohammadein A. A. , Mansour M. A. , Gorla R. S. R.

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1999

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tom Vol. 4, no 1

25-34

EN

The theory of micropolar fluids due to Eringen is used to formulate a set of boundary layer equations for the heat transfer from an arbitrarily stretching surface with non-uniform surface temperature. A two dimensional similarity solution to the governing momentum, angular momentum and energy equations is presented. The effects of the boundary conditions used for the microrotation term are discussed. Numerical data for the friction factor and Nusselt number has been shown graphically for a range of values of the material properties.

12

Flows of generalized second grade fluids in rectilinear channels

100%

Walicki E. , Walicka A.

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1999

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tom Vol. 4, no 2

375-395

EN

In this work the authors consider laminar flows of generalized second grade fluids in rectilinear channels. These fluids do exhibit both viscoplastic and viscoelastic behaviour. In the model of fluid under analysis the viscoplastic behaviour is described by Shulman equation, and the viscoelastic behaviour by Rivlin-Ericksen equation for a second grade fluid. A connection between the above mentioned behaviours is modelled in the following way: the constant coefficent of shear viscosity of a fluid of second grade fluid is replaced by a shear viscosity taken from a viscoplastic fluid modelled by Shulman equation. If the normal stress coefficients are set equal to zero, this model reduces to the standard viscoplastic Shulman model. The solutions are obtained for Poiseuille and Couette flows in the case of constant values of material coefficients.

13

Stability of two superposed Walters? B'viscoelastic fluids in the presence of suspended particles and variable magnetic field in porous medium

100%

Sharma R. C. , Kango S. K.

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1999

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tom Vol. 4, no 2

255-269

EN

The instability of plane interface between two superposed Walters' B' elastico-viscous fluids in porous medium has been studied to include the effects of suspended (dust) particles. It is found that the system is stable or unstable if the kinematic viscoelasticity (assumed equal for both fluids) is less than or greater than the medium permeability divided by medium porosity, for the potentially stable arrangement whereas the system is unstable for the potentially unstable arrangement. This problem has also been studied for electrically conducting Walters' fluid in the presence of a variable horizontal magnetic field. For a potentially stable case, the results are the same as in a hydrodynamic case. However, for a potentially unstable case, the magnetic field has got stabilizing effect and completely stabilizes certain wave-number band if kinematic viscoelasticity is less than the medium permeability divided by medium porosity.

14

Hydrostatic lubrication: the principle and applications of flow self-regulation

100%

Bassani R.

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1999

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tom Vol. 4, no 2

291-310

EN

A concise outline is presented of the principle of self-regulated flow rate in hydrostatic lubrication and some interesting applications are described on kinematic pairs and their systems. The principle permits a continuous and automatic distribution of the total flow in partial constant flows in the recesses of hydrostatic bearings due to their special shape. Studies and results obtained and presented here refer to: - generalities of the principle, pointed out by a bearing, - self-regulated hydrostatic screw and nut, - self regulated hydrostatic screw and nut with rectangular threads, - system of self-regulated hydrostatic pads.

15

Radiation and free convection flow past a moving plate

100%

Raptis A. , Perdikis C.

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1999

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tom Vol. 4, no 4

817-821

EN

This paper deals with the effects of thermal radiation by taking into account the free convection flow over a moving plate. The fluid considered is a gray, absorbing-emitting radiation but non-scattering medium.

16

Analytical fluid film force in the turbulent journal bearings

100%

D'Agostino V. , Guida D. , Ruggiero A.

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1999

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tom Vol. 4, no spec.

25-31

EN

The aim of this paper is to illustrate a method to determine the analytical description of non-steady fluid film force and of the stiffness and damping coefficients for the "short" liquid-lubricated journal bearings in a fully developed turbulent flow regime. The equation goveming the distribution of pressure around the bearing has been solved analytically; the models has been developed assuming lubricant flow is isoviscous.

17

Transient natural convection in a vertical channel

100%

Paul T. , Jha B. K. , Singh A. K.

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2001

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tom Vol. 6, no 4

913-922

EN

This paper describes a theoretical analysis of transient motion of a viscous incompressible fluid in a vertical channel. The motion of the fluid is caused by the buoyancy force arising from the temperature gradient as a result of constant heat flux at one wall and an adiabatic condition on the other wall. Expressions for the velocity and temperature fields are derived with the help of the Laplace transform technique. The influence of the various parameters is extensively discussed with the help of graphs. It has been observed that the temperature is not influenced by the presence of an adiabatic condition on the other plate for large values of the Prandtl number.

18

Combined thermal and diffusion buoyancy effects in micropolar fluids

100%

Mansour M. A. , Mohammadein A. A. , El Kabeir S. M. , Gorla R. S. R.

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2001

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tom Vol. 6, no 2

551-572

EN

A regular perturbation analysis is presented for the laminar natural convection flows of micropolar fluids with temperature dependent viscosity: a freely-rising plane plume, the flow above a horizontal line source on an adiabatic surface (a plan wall plume) and the flow adjacent to a vertical uniform flux surface. While these flows have well-known power-law similarity solutions when the fluid viscosity is taken to be constant, they are non-similar when the viscosity is considered to be a function of temperature. A flow adjacent to a vertical isothermal surface is also analyzed for comparison in order to estimate the extent of validity of the perturbation analysis. The formulation used here provides a unified treatment of variable viscosity effects on those four flows. Computed first-order perturbation quantities are presented for all four flows. The velocity, microrotation distribution, temperature and concentration profiles are shown. Numerical results are presented for the local Nusselt number and Sherwood number, wall shear stress and wall couple stress.

19

The axisymmetric compressible boundary layer flow along a circular cylinder

100%

Elliott J. W.

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2000

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tom Vol. 5, no 3

715-751

EN

A numerical and analytical investigation of the compressible axisymmetric boundary-lager flow over a circular cylinder is presented for both adiabatic flow and the case of heated or cooled walk. First, a numerical solution to the governing equations is presented for a variety of wall conditions. The remainder and majority of the paper is then concerned with an analysis of the far-downstream flow where curvature becomes a dominant feature. Here the flow takes on a double structure, with an Oseen type of outer flow. The problem reduces to matching to an inner solution which, in contrast to the incompressible case, is found to be non-trivial. Three forms of the inner solution are constructed, firstly to justify obtaining a new result and secondly to rebut the assertion that matching is only possible for a single approach. Further the use of a general power law form for the viscosity law is considered. The resulting asymptotic forms are then compared with the numerical results of the far downstream flow.

20

Hydrodynamic and thermal analysis of Fluidyne heat engine

100%

Arslanturk C. , Ozguc A. F.

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2000

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tom Vol. 5, no 2

435-449

EN

Fluidyne is an easy-to-build and quiet heat engine using low-grade heat sources and not having any moving solid parts. Although Fluidyne?s efficiency is quite low compared with efficiencies of other heat engines, it has an important advantage of using recovered heat. In this study, a mathematical model that analyses Fluidyne is developed. The model utilizes the equations of conservation of mass written for liquid columns and working fluid. Sets of differential equations are solved using Runge-Kutta Method. In order to investigate the validation of the model, theoretical results are compared with experimental results and the results in literature.