Free convection about a sphere at small Grashof number

A numerical model for the free convective flow about an isothermally heated sphere was solved by the series truncation method, with consideration given to a Grashof number of the order unity. The solution method was extended to the situation of free convection between concentric rotating spheres. Expressions were defined for the local and averaged Nusselt numbers on the sphere and the Nusselt number for various values of the Grashof number are presented. It was found that, for small values of the Grashof number (0.01-0.1), the isotherms were nearly concentric spheres and were conduction dominated.