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1

An asymptotic analysis of convection in boundary layer flows in the presence of a chemical reaction

Shateyi S., Sibanda P., Motsa S. S.

Archives of Mechanics

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2005

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Vol. 57, nr 1

25--41

EN

In this study we investigate the stability of two-dimensional disturbances imposed on a boundary layer flow over a semi-infinite flat plate in the presence of a reacting chemical species. Species concentration levels are assumed to be small, what is typical for many processes in water and in atmospheric air. We exploit the multi-deck structure of the flow in the limit of large Reynolds numbers to analyze asymptotically the perturbed flow. The neutral eigenrelations are obtained implicitly and limiting cases for large buoyancy and reaction kinematics are investigated. The results show some interesting effects of the Damkohler number on the wave number and wave speed of the disturbed flow.

2

Unsteady free convection flow in the stagnation-point region of a rotating sphere embedded in a porous medium

Hassanien I. A., Ibrahim F. S., Omer G. M.

Mechanics and Mechanical Engineering

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2004

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Vol. 7, nr 2

89-98

EN

The problem of the unsteady free convection flow in a fluid saturated porous medium of a rotating sphere in the presence of a solid matrix exerting first and second resistance is studied. Numerical solutions are obtained for the cases of constant wall temperature (CWT) and constant heat flux (CHF). The non-linear coupled partial differential equations governing the flow have been solved numerically using finite difference. The effects of the first resistance parameter ξ, the buoyancy parameter λ, the Prandtl number Pr, the variation of the angular velocity with time (ε > 0) on the skin friction and heat transfer rate ue discussed, is shown the figures. It is found that the buoyancy force enhanced both the skin fraction and the heat transfer rate. The effect of the presence of the first resistance decreases the skin friction and the heat transfer rate.

3

Effect of the magnetic field on forced convection flow along a wedge with variable viscosity

Dimian M. F.

Mechanics and Mechanical Engineering

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2004

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Vol. 7, nr 1

107-117

EN

This paper presents a study of the flow of a viscous incompressible fluid along a heated wedge, taking into account the variation of the viscosity with temperature. The flow is under the influence of a magnetic field B(x) along y direction applied perpendicular to the surface of the boundary layer along x direction and an electric field E(x) along z direction. The boundary layer equations are transformed to nonlinear ordinary differential equations and are solved numerically. The effects of the magnetic field on the velocity and the temperature and the shear stress on the surface (Tw) are studied. It is found that the velocity of the fluid increases with increasing the magnetic field parameter M, with the other parameters kept constant. It is also established that the temperature of the wedge decreases with increasing M value. The value of the skin friction increases whereas the rate of heat transfer decreases owing to increasing the magnetic field parameter and also according to decreasing the viscosity.