Stability of a free-convection boundary layer on a vertical permeable plate

The stability of a free-convection boundary layer on vertical permeable and impermeable plates with respect to small perturbations is investigated in the context of linear theory. For flow on an isothermal plate, it is found that as the injection intensity increases, flow stability first decreases and then tends to a constant value corresponding to asymptotically strong injection. For an impermeable nonisothermal surface, it is shown that the critical Grashof number increases linearly with the nonisothermality parameter and the effect of thermal waves on stability becomes more pronounced. The effect of injection on flow stability characteristics is the same for nonisothermal and isothermal plates.