ROTATING RAYLEIGH-BENARD CONVECTION - ASPECT-RATIO DEPENDENCE OF THE INITIAL BIFURCATIONS

The initial bifurcations in rotating Rayleigh-Benard convection are st udied in the range of dimensionless rotation rate 0 < OMEGA < 2150 for a cylindrical cell with an aspect ratio of 2.5. We used simultaneous optical-shadowgraph, heat-transport, and local-temperature measurement s to determine the stability and characteristics of the azimuthally pe riodic wall convection state. We also show that the second transition corresponds to the onset of bulk convection. Our results for critical Rayleigh numbers, precession frequencies, and critical mode numbers ag ree well with theoretical results. The dynamics of the wall convection state can be described by a complex Ginzburg-Landau amplitude equatio n.