THERMAL-INSTABILITY OF FLOWS WITH A HORIZONTAL TEMPERATURE-GRADIENT

The effect of horizontal heat advection on the thermal instability is studied for a general class of horizontal flows comprising forced and temperature-induced flow components as well as a possible net heat tra nsport. The instability is usually triggered by an unstable layer of h eight h(u), which is caused by the nonlinear vertical temperature prof ile typical for such flows. As h(u), decreases, the critical values of the Rayleigh and the wave number, defined with respect to this unstab le layer, become independent of h(u). This behavior can be explained b y the scaling properties of the flow in the unstable region.