DIRECT SIMULATION OF WAVE INTERACTIONS IN UNSTEADY NATURAL-CONVECTION IN A CAVITY

Numerical solutions for unsteady natural convection flow in a square cavity with differentially heated side walls are obtained using an implicit second-order time-accurate finite volume scheme, and briefly compared to experimental data reported elsewhere. The results predict the occurrence of a cavity scale seiche, the presence of waves in the vertical thermal boundary layer that travel from the walls into the horizontal intrusions that form on the horizontal boundaries, and a region of strong divergence at the upstream end of the intrusions. These three mechanisms are observed to interact at a Rayleigh number of 5 x 10(9) to produce a mixing patch in the intrusion, suggestive of a transition to turbulence. The net heat transfer and the approach to steady state are strongly influenced by the presence of the waves.