
Archive issue  vol.4 No.2
1.
RADIATIVE AND VARIABLE VISCOSITY EFFECTS
ON A FREE CONVECTION FLOW OVER A
VERTICAL STRETCHING SURFACE
M.A.MANSOUR
Department of Mathematics, Faculty of Science,
Assiut University, Assiut, EGYPT
R.S.R. GORLA
Department of Mechanical Engineering,
Cleveland State University, Cleveland OH 44115, USA
The effects of radiation and variable viscosity on natural convection heat transfer from a vertical stretching sheet with surface mass transfer is analysed. A three dimensional similarity solution to the governing momentum and energy equations is presented. Numerical data for the friction and Nusselt number have been tabulated.

Key words: 
radiation, heat transfer, free convection, stretching surface. 
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2.
TRANSIENT FREE CONVECTION FLOW OF VISCOUS DISSIPATIVE
FLUID PAST A SEMIINFINITE VERTICAL PLATE
V.M. SOUNDALGEKAR
31A12, Brindavan Society, Thane (400 601), INDIA
B.S. JAISWAL
Birla College, Kalyan (421 304), INDIA
A.G. UPLEKAR
Patkar College, Goregaon, Mumbai (400 062), INDIA
H.S. TAKHAR
Dept. of Engineering, Manchester University,
Manchester, M13 9PL, UNITED KINGDOM
Transient free convection flow of an incompressible viscous fluid past a semiinfinite vertical plate has been studied by using an implicit finitedifference technique, which is always stable and convergent. The effect of the dissipation parameter ? on time to reach steadystate is studied. It is observed that time required to reach steadystate temperature increases with the increasing Prandtl number of fluid. Also there is a rise in the average skinfriction and a fall in the average Nusselt number due to greater viscous dissipative heat.

Key words: 
transient flow, viscous dissipation effects. 
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3.
RADIATION INTERACTION ON FORCED AND FREE CONVECTION
ACROSS A HORIZONTAL CYLINDER
M.A. HOSSAIN, M. KUTUBUDDIN
Department of Mathematics, University of Dhaka,
Dhaka 1000, BANGLADESH
H.S. TAKHAR
School of Engineering, University of Manchester,
Manchester, M13 9PL, UNITED KINGDOM
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 nonsimilar 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, R_{d} and the surface temperature parameter, __ , for fluids having the Prandtl number of 0.7. Results are presented in terms of local skinfriction 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 R_{d} and __ , in the entire pure forced to pure free convection regimes.

Key words: 
radiation effects, mixed convection flow. 
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4.
THERMODYNAMICAL MODELLING OF BEHAVIOR OF
ELASTOVISCOELASTIC LAYERED STRUCTURE
B.T. MARUSZEWSKI, H. KAMIŃSKI and R. STAROSTA
Poznań University of Technology, Institute of Applied Mechanics,
ul. Piotrowo 3, 60965 Poznań, POLAND
The thermodynamical model, derivation of the field equations, proper boundary conditions, analytical and numerical solutions to an elastoviscoelastoelastic problem in a layered structure have been presented. Three different kinds of loading have been applied to the structure. A spacetime analysis of displacements in each layer has been done.

Key words: 
viscoelasticity, biomechanics, computer simulation. 
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5.
STABILITY OF TWO SUPERPOSED WALTERS' B'VISCOELASTIC
FLUIDS IN THE PRESENCE OF SUSPENDED PARTICLES AND
VARIABLE MAGNETIC FIELD IN POROUS MEDIUM
R.C. SHARMA and S.K. KANGO
Department of Mathematics, Himachal Pradesh University
Summer Hill, Shimla171005, INDIA
The instability of plane interface between two superposed Walters' B' elasticoviscous 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 wavenumber band if kinematic viscoelasticity is less than the medium permeability divided by medium porosity.

Key words: 
hydromagnetic superposed fluids, Walters' fluid, porous medium. 
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6.
FORCED CONVECTIVE HEAT TRANSFER IN A PARALLELPLATE
CHANNEL WITH A POROUS CORE
A.V. KUZNETSOV
Department of Mechanical and Aerospace Engineering
North Carolina State University, Campus
Box 7910, Raleigh, NC 276957910, USA
This paper presents an analytical study of the fully developed forced convection in a parallelplate channel. The central part of the channel is occupied by a porous core and the peripheral part of the channel is occupied by a clear fluid. A uniform heat flux is imposed at the walls of the channel. The BrinkmanForchheimerextended Darcy equation is utilized as a momentum equation in the porous region. This formulation accounts for both viscous and quadratic drag effects in the porous region. Analytical solutions for the velocity and temperature distributions, as well as for the Nusselt number are obtained.

Key words: 
porous medium, forced convection, BrinkmanForchheimerextended Darcy equation, interface region. 
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7.
HYDROSTATIC LUBRICATION: THE PRINCIPLE AND APPLICATIONS
OF FLOW SELFREGULATION
R. BASSANI
Dipartimento di Costruzioni Meccaniche e Nucleari,
Universita di Pisa, Pisa, ITALY
A concise outline is presented of the principle of selfregulated 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,
 selfregulated hydrostatic screw and nut,
 self regulated hydrostatic screw and nut with rectangular threads,
 system of selfregulated hydrostatic pads.

Key words: 
lubrication, hydrostatic, selfregulation. 
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8.
TESTS ON A NEW METHOD FOR NUMERICAL SOLUTION
TO THE NAVIERSTOKES EQUATIONS.
PART I: PLANE UNSTEADY FLOW IN FINITE, RECTANGULAR DOMAINS
M.E. KLONOWSKA
Institute of Oceanology, Polish Academy of Sciences
81 712 Sopot, POLAND
M. KOŁODZIEJCZYK
Department of Mechanics, Technical University of Białystok
15 351 Białystok, POLAND
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 NavierStokes 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 NavierStokes 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.

Key words: 
NavierStokes equations, elimination of pressure. 
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9.
ANALYSIS OF POLYMERS FLOW THROUGH
DIES OF FORMING DEVICES
A. WALICKA
Technical University of Zielona Góra
Department of Mechanics,
ul. Szafrana 2, 65516 Zielona Góra, POLAND
The steady laminar flow of molten polymer modelled by viscoplastic fluid is considered, through a narrow space between two fixed surfaces of revolution. The problem is described by boundary layer equations. Using the method of averaged inertia one obtains the formulae expressing the pressure distribution. Generally, the flow of viscoplastic fluids given by the nonlinear model of Shulman is considered. The flows of polymers modelled by the viscoplastic fluids of Vočadlo, Herschel  Bulkley, Ostwald  de Waele and Newtonian are discussed in detail. Numerical examples of pressure distributions in the clearance between parallel disks and concentric spherical surfaces are presented.

Key words: 
boundary layer equations, fixed surfaces of revolution, forming devices, polymers flow, viscoplastic fluids. 
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10.
INTERIA EFFECT IN THE SQUEEZE FILM OF
A COUPLESTRESS FLUID IN BIOLOGICAL BEARINGS
E. WALICKI and A. WALICKA
Technical University of Zielona Góra, Dept. of Mechanics, ul. Szafrana 2,
65016 Zielona Góra, POLAND
Couplestresses affect lubrication problem when additives are used or lubricant contains longchain molecules. Such couplestresses may have a considerable effect on the behaviour of bearings in practice. The influence of couplestress and lubricant inertia on mechanical parameters of the curvilinear thrust bearing with squeeze film is considered. The simulation of the squeezefilm behaviour of a human joint modelled as a spherical bearing is discusses as an example. It is shown that the influence of couplestresses on the characteristics of the discussed bearing is considerable but the inertia effect is significant and not negligible. Both the effects  couplestress and inertia  provide an enhancement in the pressure distribution and in the loadcarrying capacity.

Key words: 
couplestress fluids, inertia effect, synovial joints, spherical bearing, squeeze film characteristics. 
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11.
FLOWS OF GENERALIZED SECOND GRADE FLUIDS
IN RECTILINEAR CHANNELS
E. WALICKI and A. WALICKA
Technical University of Zielona Góra, Department of Mechanics
ul. Szafrana 2, P.O.Box 47, 65016 Zielona Góra, POLAND
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 RivlinEricksen 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.

Key words: 
second grade fluids, rectilinear channels, viscoplastic and viscoelastic behaviour. 
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