WAVE PROPERTIES OF NATURAL-CONVECTION BOUNDARY-LAYERS

The thermal boundary layer on the wall of a side-heated cavity at early time is known to exhibit a complex travelling wave during growth to steady state and a similar feature is observed on isolated heated semi-infinite plates. Direct numerical solutions of the Navier-Stokes equations together with a linearized stability analysis are used to study the character of the flow at early time in detail. It is demonstrated that the cavity flow is essentially identical to the plate flow, and that for early time the flow is one-dimensional. Using the stability results it has been possible to accurately describe the form of the observed instability, as well as to reconcile a previously unexplained discrepancy in the speed of development of the flow.