Compressibility effects on the Kelvin–Helmholtz and Rayleigh–Taylor instabilities between two immiscible fluids flowing through a porous medium

Abstract

We examine analytically the Kelvin–Helmholtz stability of two compressible superposed viscous fluids flowing through porous medium. The dispersion relationship is derived and evaluated for special cases adopting the normal mode procedure. The results have been compared with the statics (RTI) and incompressible cases. It is shown that the behaviour of KHI tends to RTI behaviour if the difference in the initial velocity of two fluids (U2 − U1) is small. For incompressible KHI, the kinematic viscosity induces stability. The permeability has also stabilizing role on the perturbation’s growth, but the growth rate increases as permeability increases. The porosity has destabilizing effect on KHI for the case of small values of porosity, while for large values, it has stabilizing effect. The compressibility parameters (the specific heats ratio and pressure at equilibrium state) have stabilizing role on KHI. The behaviour of normalized growth rate of a compressible KHI model with the porosity effect in most cases capitulates to effect of porosity.