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The large-scale circulation in turbulent Rayleigh--B\'enard convection in an aspect ratio 1 cell at large Rayleigh numbers

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We present temperature measurements in turbulent Rayleigh–Bénard convection (RBC) over the Rayleigh number range
3.0 × 1013 < Ra < 1.3 × 1014 and at constant Prandtl number Pr ≈ 0.8. The RBC sample, known as the High-Pressure Convection
Facility (HPCF) of Göttingen, is an upright cylinder of aspect ratio Γ = 1.00. Using three horizontal rows of thermistors at different
heights in the sample, we determined the orientation angle of the large-scale circulation (LSC) plane. Results identify a well established
single-roll LSC with a periodic “torsional” mode with a frequency fc . The values of fc are consistent with the frequencies fl obtained from power spectra P (f ) of temperature time series taken at mid-height of the sample. The non-dimensionalized frequencies fc are well described by a power law. No evidence for a LSC has been observed in similar experiments using a Γ = 0.50 cell.

Author(s):

Dennis Paulus Maria van Gils    
Max Planck Institute for Dynamics and Self-Organization
Germany

Xiaozhou He    
Max Planck Institute for Dynamics and Self-Organization
Germany

Guenter Ahlers    
University of California, Santa Barbara
United States

Eberhard Bodenschatz    
Max Planck Institute for Dynamics and Self-Organization
Germany