Traveling-wave and vortex states in rotating Rayleigh-Benard convection

Experimental results on states of rotating Rayleigh-Benard convection in wa ter with a Prandtl number of 6.4 are presented. Using precision heat transp ort measurements and optical shadowgraph imaging, we have explored the side wall traveling-wave state in cylindrical convection cells with radius-to-he ight ratios Gamma = 1, 2.5, and 5. The critical Rayleigh number and precess ion frequencies for the wall mode were measured as a function of a dimensio nless rotation rate and are compared to theoretical predictions. The onset of bulk convection and its pattern wave number are found to agree quite clo sely with predictions of Chandrasekhar's linear stability analysis. Vortex states at higher Rayleigh number are also described and characteristics of the thermal vortices including the vortex circulation and the frequency of collective vortex motions are presented. (C) 1998 Elsevier Science Ltd. All rights reserved.