Velocity measurements in rotating Rayleigh-Bénard convection and the Boundary Zonal Flow
ORAL
Abstract
We report on velocity measurements in rotating Rayleigh-Bénard convection (RBC). Experiments are conducted in a cylindrical plexiglass transparent cell
with diameter (D) and height (H) of 20 cm, resulting in the aspect ratio Γ=D/H=1. As working fluid, we use mixtures of water and glycerol, resulting in Prandtl numbers between 6.6≤Pr≤75, and Rayleigh numbers in the range 108≤Ra≤3×109. The cell rotates around its cylinder axis with rotation rates that correspond to Ekman numbers 1.5×10-5≤Ek. We measure horizontal velocity components at a cross-section at half height using Particle Image Velocimetry. With our results we show the first direct measurements of the Boundary Zonal Flow - BZF, which develops near the sidewall and was recently discovered in numerical simulations (see Zhang et al., Phys.Rev.Lett. 2020) and localised temperature measurements (Wedi et al., JFM 2021). We analyse the thickness δ0 of the near wall region as well as typical velocities therein as function of Pr, Ra, and Ek, and compare these results with numerical simulations.
with diameter (D) and height (H) of 20 cm, resulting in the aspect ratio Γ=D/H=1. As working fluid, we use mixtures of water and glycerol, resulting in Prandtl numbers between 6.6≤Pr≤75, and Rayleigh numbers in the range 108≤Ra≤3×109. The cell rotates around its cylinder axis with rotation rates that correspond to Ekman numbers 1.5×10-5≤Ek. We measure horizontal velocity components at a cross-section at half height using Particle Image Velocimetry. With our results we show the first direct measurements of the Boundary Zonal Flow - BZF, which develops near the sidewall and was recently discovered in numerical simulations (see Zhang et al., Phys.Rev.Lett. 2020) and localised temperature measurements (Wedi et al., JFM 2021). We analyse the thickness δ0 of the near wall region as well as typical velocities therein as function of Pr, Ra, and Ek, and compare these results with numerical simulations.
*We acknowledge financial support by the Deutsche Forschungsgemeinschaft (DFG) through grant WE 5011/4-1, and from the European High-Performance Infrastructure in Turbulence program (EuHIT). DF received a travel grant by the Deutsch Akademische Austauschdienst - DAAD.
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Publication: Wedi, Marcel, Moturi, Viswa M., Funfschilling, Denis, Weiss, Stephan. Experimental evidence for the Boundary Zonal Flow. Submitted to J. Fluid Mech.
Presenters
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Marcel Wedi
- Max Planck Institute for Dynamics and Self-Organization