The effect of radiation on free convection flow of fluid with variable viscosity from a porous vertical plate

The effect of thermal radiation on the natural convection flow along a uniformly heated vertical porous plate with variable viscosity and uniform suction velocity was investigated numerically. The fluid considered in this study is of an optically dense viscous incompressible fluid of temperature-dependent viscosity. The laminar boundary layer equations governing the flow are shown to be nonsimilar. The governing equations are analyzed using a variety of methods: (i) a series solution for smalt values of xi (a scaled streamwise coordinate depending on the transpiration); (ii) an asymptotic solution for large values of xi; and (iii) a full numerical solution using the Keller box method. The solutions are expressed in terms of the local shear stress and the local heat transfer rate. The working fluid is taken to have Prandtl number Pr = 1, and the effects of varying the viscosity variation parameter, gamma, the radiation parameter, R-d, and the surface temperature parameter, theta (w), are discussed. (C) 2001 Editions scientifiques et medicales Elsevier SAS.