RAYLEIGH-BENARD CONVECTION IN A SMALL ASPECT RATIO ENCLOSURE .1. BIFURCATION TO OSCILLATORY CONVECTION

The present numerical study documents bifurcation sequences for Raylei gh-Benard convection in a rectangular enclosure with insulated sidewal ls. The aspect ratios are 3.5 and 2.1 and the Boussinesq fluid is wate r (average temperature of 70-degrees-C) with a Prandtl number of 2.5. Two transitions are documented numerically. The first transition is fr om steady-state to oscillatory flow and the second is a subharmonic bi furcation as the Rayleigh number is increased further. The dynamics of the flow and temperature field is analyzed in detail for the subcriti cal steady con vection and the supercritical oscillatory convection. T he numerical results compared well with experiments, both qualitativel y and quantitatively.