Effect of anisotropy and boundary conditions on Darcy and Brinkman porous penetrative convection

Abstract

Abstract We investigate the effects of anisotropic permeability and changing boundary conditions upon the onset of penetrative convection in a porous medium of Darcy type and of Brinkman type. Attention is focussed on the critical eigenfunctions which show how many convection cells will be found in the porous layer. The number of cells is shown to depend critically upon the ratio of vertical to horizontal permeability, upon the Brinkman coefficient, and upon the upper boundary condition for the velocity which may be of Dirichlet type or constant pressure. The critical Rayleigh numbers and wave numbers are determined, and it is shown how an unconditional threshold for nonlinear stability may be derived. Highlights Shows how number of convection cells depends upon the temperature of the upper layer and the anisotropy of the permeability Shows how number of convection ceels depends upon the temperature of the upper layer and the Brinkman coefficient Shows how number of convection cells patters depends upon the upper boundary condition on the velocity or the ambient pressure