MULTICOMPONENT CONVECTION-DIFFUSION IN A POROUS-MEDIUM

The stability of a triply diffusive fluid-saturated porous layer is in vestigated. A linear stability analysis similar td that of Pearlstein et al [1] is presented. This allows us to make a thorough investigatio n of the topology of the neutral curves. For some values of the therma l and solute diffusivities we obtain highly unusual neutral curves, in particular a heart-shaped, disconnected oscillatory curve. The effect of this is that three critical Rayleigh numbers are required to fully specify the linear stability criteria, a novel result in porous conve ction. The influence of nonlinear terms is likely to have important co nsequences for the experimental realisation of the linear results and so we investigate the nonlinear stability of the problem by making use of the energy method. This provides an unconditional nonlinear stabil ity boundary and enables us to identify possible regions of subcritica l instability.