Contributed by the Heat Transfer Division for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received by the Heat Transfer Division April 3, 2001; revision received September 6, 2001. Associate Editor: M. Faghri.

Buoyant convection in an enclosure induced by uniform internal heat generation has been extensively studied (Acharya and Goldstein 1, Bergholz 3, Fusegi et al. 4, Kulacki and Goldstein 6, May 10). One canonical layout is a rectangular cavity with two vertical sidewalls at constant temperatures and two insulated horizontal endwalls, with large Rayleigh number Ra $>105,$ Prandtl number O(1) and cavity aspect ratio O(1). In particular, when both vertical sidewalls are maintained at the same temperature $T0,$ the overall flow is expectedly symmetric about the vertical centerline. In each half-cavity, the fluid rises (sinks) near the centerline (near the vertical sidewall) region, which forms a single...