Transient natural convection in an eccentric porous annulus between horizontal cylinders

The problem of transient natural convection in a constant-porosity medium between two eccentric horizontal circular cylinders at uniform but different temperatures is studied numerically. The non-Darcian effects as well as the acceleration terms are taken into consideration in the momentum equation. The governing equations, in terms of vortxcity, stream function, and temperature, are expressed in a body-fitted coordinate system and solved numerically by the finite-difference method. Results were obtained for steady and transient heat transfer and fluid flow characteristics in eccentric porous annuli at a Prandtl number of O.S, with the Rayleigh number ranging from 10² to 10⁷, for various radii ratios, eccentricities, and eccentric angles.