STABILITY ANALYSIS OF FREE-CONVECTION FLO WS IN AN ANNULAR POROUS LAYER

Two studies are presented in order to determine the criteria for the o nset of two-dimensional (unicellular or multicellular) or three-dimens ional free convection flows, in an annular porous laver. A 2D and 3D n umerical simulation is performed with a spectral collocation-Chebyshev method. An analytical approach for narrow gaps is also presented. The solution is obtained by means of a regular perturbation method in pow ers of:the dimensionless gap width. Computations are made using symbol ic algebra code. This solution is used for a stability analysis. Irt b oth cases, the influence of the longitudinal aspect ratio and the rela tive gap width is investigated.