RAYLEIGH-BENARD CONVECTION IN A SMALL ASPECT RATIO ENCLOSURE .2. BIFURCATION TO CHAOS

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. The transition to chaos observed in the simulations and experiments is similar to the period-doubling (Feigenbaum) route to chaos. However, special symmetry conditions must be imposed numerically, otherwise the route to chaos is different (Ruelle-Takens-Newhouse). In particular, the Feigenbaum route to chaos can be realized only if the oscillating velocity and temperature field preserves the fourfold symmetry that is observed in the mean flow in the horizontal plane.