Linear stability of differentially heated developing layers

Heterogeneous shear layers, characterized by the presence of a wake deficit and a Gaussian temperature profile, are considered. Unstable mode characteristics are interpreted in terms of a five-parameter set which describes the velocity ratio and the thicknesses and strengths of the wake component and temperature spike. In the absence of a wake deficit, the Kelvin-Helmholtz mode is inhibited as density gradients increase. Stabilization of this mode is weak (strong) when the density profile thickness is larger (smaller) than that of the shear layer. When a wake component is present, stabilization of the Kelvin-Helmholtz instability is no longer observed. In this case, the growth rate of unstable Kelvin-Helmholtz waves is found to be weakly sensitive to the presence of a heated region and to the details of the wake deficit.