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1

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.

2

Combined heat and mass transfer by free convection past an inclined flat plate

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

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 2

473-487

EN

The steady laminar free convection boundary layer over the upper surface of a semi-infinite flat plate which is inclined at a small angle to the horizontal under the combined buoyancy effects of thermal and mass (concentration) effects is theoretically studied in this paper. Series solutions are obtained for both positive and negative inclinations of the plate, valid near the leading edge of the plate. Also, a series solution, which is valid only for positive inclinations and far downstream from the leading edge of the plate, is determined. The Keller-box scheme is then used to complete the solution in the regions where neither series is adequate using the full boundary layer equations. Results for the skin friction coefficient, the local Nusselt and Scherwood numbers are presented. Also, the variation of the separation point of the boundary layer with the Schmidt number is determined and shown on a graph.

3

Radiation interaction on forced and free convection across a horizontal cylinder

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

Applied Mechanics and Engineering

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1999

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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.

4

Effect of radiation on mixed convection boundary layer flow along a vertical cylinder

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

Applied Mechanics and Engineering

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1998

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Vol. 3, no 3

393-404

EN

Mixed convection flow of an optically dense viscous incompressible fluid along a vertical cylinder including the effects of radiation has been studied when the surface temperature is kept uniform. With appropriate transformations, the boundary layer equations governing the flow are reduced to local non-similarity equations. Solutions to the governing equations are obtained by employing an implicit finite difference method together with the Keller box scheme, as well the local non-similar method with a second order trunction, for values of the transverse curvature parameter, x, in the range [0,10]. Effects of the pertinant parameters, such as the radiation parameter, Rd, the surface temperature parameter, qw, and the buoyancy parameter W , taking Prandtl number, Pr, equal to 0.7, on the local skin-friction and the local Nusselt are explored in this stidy.