KUPPERS-LORTZ TRANSITION AT HIGH DIMENSIONLESS ROTATION RATES IN ROTATING RAYLEIGH-BENARD CONVECTION

We show that for rotating Rayleigh-Benard convection over a range of d imensionless rotation rates 270 < OMEGA < 2500, bulk convection struct ures are Kuppers-Lortz unstable near onset. We used optical shadow-gra ph imaging to visualize the pattern dynamics, found switching angles o f approximately 60-degrees, and observed separate spatial domains wher e switchings took place at different times. The characteristic switchi ng frequencies were found to depend weakly on the rotation rate. Finit e-size and boundary effects were observed to complicate the switching dynamics close to onset.