Stability of vertical thermal boundary-layer flow in a porous medium

We consider the linearised stability characteristics of the thermal boundary layer induced by the uniform heating of a semi-infinite vertical surface embedded in a fluid - saturated porous medium. In this paper attention is restricted to two-dimensional disturbances far from the leading edge. This analysis complements and extends the direct numerical simulation of Rees [1993] which shows that the flow is stable at locations sufficiently close to the leading edge. In this asymptotic regime we also find that wave disturbances decay. However, the rate of decay decreases as the distance downstream of the leading edge increases.