LSC Oscillations in a Liquid Metal

We present experimental results of liquid metal Rayleigh Bénard convection in a Gamma = D/H = 2 cylindrical tank. The tank is filled with liquid gallium that has a Prandtl-number Pr = 0.03. Ultrasound Doppler velocimetry is used in this study to measure the instantaneous velocity distribution along four different measuring lines. This technique is a useful tool to measure the velocities in opaque fluids, such as liquid metals non-invasively. Furthermore, a total number of 29 thermocouples is used to monitor the temperature in the experiment. Thus, the experimental set-up allows for a simultaneous analysis of the velocity and temperature field. We observed a strong oscillatory behaviour of the LSC in both, the velocity and temperature signal whose characteristic behaviour remains unchanged over the investigated range of 7x10^4 < Ra < 6x10^6. We analysed the three dimensional structure of the oscillation and compare the results to direct numerical simulation, which are in excellent agreement to the experimental observation.