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1

Convective heat transfer in a micropolar fluid over an unsteady stretching surface

Prasad K. V., Vaidya H., Vajravelu K.

International Journal of Applied Mechanics and Engineering

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2016

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Vol. 21, no. 2

407--422

EN

An unsteady boundary layer free convective flow and heat transfer of a viscous incompressible, microploar fluid over a vertical stretching sheet is investigated. The stretching velocity is assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along the x-axis so that the sheet is stretched, keeping the origin fixed in the micropolar fluid. The transformed highly non-linear boundary layer equations are solved numerically by an implicit finite difference scheme for the transient, state from the initial to the final steady-state. To validate the numerical method, comparisons are made with the available results in the literature for some special cases and the results are found to be in good agreement. The obtained numerical results are analyzed graphically for the velocity, the microrotation, and the temperature distribution; whereas the skin friction, the couple stress coefficient and the Nusselt number are tabulated for different values of the pertinent parameters. Results exhibit a drag reduction and an increase in the surface heat transfer rate in the micropolar fluid flow compared to the Newtonian fluid flow.

2

Axisymmetric mixed convective MHD flow over a slender cylinder in the presence of chemically reaction

Prasad K. V., Vaidya H., Vajravelu K., Datti P. S., Umesh V.

International Journal of Applied Mechanics and Engineering

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2016

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Vol. 21, no. 1

121--141

EN

The present analysis is focused on the study of the magnetic effect on coupled heat and mass transfer by mixed convection boundary layer flow over a slender cylinder in the presence of a chemical reaction. The buoyancy effect due to thermal diffusion and species diffusion is investigated. Employing suitable similarity transformations, the governing equations are transformed into a system of coupled non-linear ordinary differential equations and are solved numerically via the implicit, iterative, second order finite difference method. The numerical results obtained are compared with the available results in the literature for some special cases and the results are found to be in excellent agreement. The velocity, temperature, and the concentration profiles are presented graphically and analyzed for several sets of the pertinent parameters. The pooled effect of the thermal and mass Grashof number is to enhance the velocity and is quite the opposite for temperature and the concentration fields.

3

Flow and heat transfer at a nonlinearly shrinking porous sheet: the case of asymptotically large powerlaw shrinking rates

Prasad K. V., Vajravelu K., Pop I.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 3

779--791

EN

The boundary layer flow and heat transfer of a viscous fluid over a nonlinear permeable shrinking sheet in a thermally stratified environment is considered. The sheet is assumed to shrink in its own plane with an arbitrary power-law velocity proportional to the distance from the stagnation point. The governing differential equations are first transformed into ordinary differential equations by introducing a new similarity transformation. This is different from the transform commonly used in the literature in that it permits numerical solutions even for asymptotically large values of the power-law index, m. The coupled non-linear boundary value problem is solved numerically by an implicit finite difference scheme known as the Keller- Box method. Numerical computations are performed for a wide variety of power-law parameters (1 < m < 100,000) so as to capture the effects of the thermally stratified environment on the velocity and temperature fields. The numerical solutions are presented through a number of graphs and tables. Numerical results for the skin-friction coefficient and the Nusselt number are tabulated for various values of the pertinent parameters.

4

Flow of a micropolar fluid on a continuous moving surface

Ishak A., Nazar R., Pop I.

Archives of Mechanics

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2006

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Vol. 58, nr 6

529-541

EN

The present paper deals with the analysis of steady boundary layer flow and heat transfer of a micropolar fluid on an isothermal continuously moving plane surface. It is assumed that the microinertia density is variable and not constant, as in many other published papers. Also, the viscous dissipation effect is taken into account. The basic partial differential equations are reduced to a system of nonlinear ordinary differential equations, which is solved numerically using the Keller-box method. Numerical results are obtained for the skin friction coefficient, local Nusselt number, as well as velocity, temperature and microrotation profiles. Results are shown in graphical form and the numerical values for the skin friction coefficient and local Nusselt number are given in the form of tables. The effects of material parameter K, Prandtl number Pr and Eckert number Ec on the flow and heat transfer characteristics are discussed.

5

Thermal radiation effects on free convection over a rotating axisymmetric body with application to a rotating hemisphere

Hossain M. A., Anghel M., Pop I.

Archives of Mechanics

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2002

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Vol. 54, nr 1

55-74

EN

This paper deals with the interaction of thermal radiation with free convection, laminar boundary-layer flow past a heated rotating axisymmetric round-nosed body of uniform surface temperature. The fluid considered is a gray, absorbing-emitting but nonscattering medium, and Rosseland approximation is used to describe the radiative heat flux. The difficulty of having a unified mathematical treatment of this problem is due to the nonsimilarity nature of the governing equations arising from the buoyant force-field and the transverse curvature of the body. The important parameters of this problem are the Planck number, Rd, the buoyancy parameter, ..., and the wall to free stream temperature ratio, .... Numerical solution of the boundary-layer equations are performed using the Keller-box method as well as the local nonsimilarity method. The theory is applied to a rotating hemisphere for a gas with Prandtl number of 0.72. The effects of the parameters ..., Rd and ... are shown on the velocity and temperature profiles, as well as on the local skin friction coefficient and local rate of heat transfer.