Unsteady free convection on a vertical cylinder with variable heat and mass flux

The unsteady natural convection boundary layer flow over a semi-infinite ve rtical cylinder is considered with combined buoyancy force effects, for the situation in which the surface temperature T-w'(x) and C-w'(x) are subject ed to the power-law surface heat and mass flux as K(partial derivative T'/p artial derivative r) = -a(x)n and D(partial derivative C'/partial derivativ e r) = -bx(m). The governing equations are solved by an implicit finite dif ference scheme of Crank-Nicolson method. Numerical results are obtained for different values of Prandtl number, Schmidt number 'n' and 'm'. The veloci ty, temperature and concentration profiles, local and average skin-friction , Nusselt and Sherwood numbers are shown graphically. The Focal Nusselt and Sherwood number of the present study are compared with the available resul t and a good agreement is found to exist.