UNSTEADY FREE CONVECTION FROM A SPHERE IN A POROUS MEDIUM WITH VARIABLE SURFACE TEMPERATURE

In this paper a transient free convection flow around a sphere \vith variable surface temperature and embedded in a porous ITIediuln has been considered. The temperature of the sphere is suddenly raised and subsequently maintained at values that varies with position on surface. The method of asynlptotic expansions is applied for SlTIal1 Rayleigh numbers and then a finite-difference scheme is used to solve the problem nunlerically for finite values of Rayleigh numbers. Transient and steady-state flow and temperature patterns around the sphere are discussed in details and a comparison bet\veen numerical and analytical results has been presented.