Linear Instability of Mixed Convection in a Vertical Annulus Filled With Porous Medium under LTNE Condition

Abstract

The stability of non-isothermal annular parallel flow through a highly permeable porous medium (such as metallic foam) is studied under a local thermal non-equilibrium (LTNE) state. An external pressure gradient and the linear varying temperature of the inner cylinder of the annulus govern the flow. The classical normal mode analysis has been considered to investigate the influence of the different controlling parameters such as Reynolds number (Re), interphase heat transfer coefficient (H), ratio of thermal conductivities (γ) and media permeability (Da) on the instability of the flow. It is found that irrespective of the other parameters, the critical instability boundary decreases sharply with Re in the range of 100 − 2000. An increment in the value of H contributes towards the stability of the basic flow. On the other hand, a destabilizing impact of γ has been observed in the present study.