Institute for Mathematics and Its Applications
Guenter Ahlers, University of California Santa Barbara
This talk will discuss results from and future prospects for experimental studies of Rayleigh-Bénard convection with rotation about a vertical axis. At dimensionless rotation rates 0 20 and for Prandtl numbers 1, measurements of Küppers-Lortz-unstable patterns have offered a unique opportunity to study spatio-temporal chaos immediately above a supercritical bifurcation. However, for > 70 and 1 patterns were found to be cellular near onset with local four-fold coordination. They differ from the theoretically expected Küppers-Lortz-unstable state. Stable as well as intermittent defect-free rotating square lattices exist in this parameter range.
Smaller Prandtl numbers ( 0.16 < < 0.7 ) can only be reached in mixtures of gases. These fluids are expected to offer rich future opportunities for the study of a line of tricritical bifurcations, of supercritical Hopf bifurcations, of a line of codimension-two points, and of a codimension-three point.