Rotating turbulent thermal convection at very large Rayleigh numbers

Turbulent convection at high Rayleigh numbers and aspect ratio 4

We report measurements of the Nusselt number, Nu, in turbulent thermal convection in a cylindrical container of aspect ratio 4. The highest Rayleigh number achieved was Ra=2× 10. Except for the last half a decade or so of Ra, experimental conditions obey the Boussinesq approximation accurately. For these conditions, the data show that the logNu–logRa slope saturates at a value close to 1/3, as ...

On the nature of fluctuations in turbulent Rayleigh–Bénard convection at large Prandtl numbers

We report experimental results for the power spectra, variance, skewness and kurtosis of temperature fluctuations in turbulent Rayleigh–Bénard convection (RBC) of a fluid with Prandtl number Pr= 12.3 in cylindrical samples with aspect ratios Γ (diameter D over height L) of 0.50 and 1.00. The measurements were primarily for the radial positions ξ = 1− r/(D/2)= 1.00 and ξ = 0.063. In both cases, ...

Large eddy simulations of turbulent thermal convection at high Rayleigh number

Heat-transport enhancement in rotating turbulent Rayleigh-Bénard convection.

We present new Nusselt-number (Nu) measurements for slowly rotating turbulent thermal convection in cylindrical samples with aspect ratio Γ=1.00 and provide a comprehensive correlation of all available data for that Γ. In the experiment compressed gasses (nitrogen and sulfur hexafluride) as well as the fluorocarbon C_{6}F_{14} (3M Fluorinert FC72) and isopropanol were used as the convecting flu...

Multiple transitions in rotating turbulent Rayleigh-Bénard convection.

Sometimes it is thought that sharp transitions between potentially different turbulent states should be washed out by the prevailing intense fluctuations and short coherence lengths and times. Contrary to this expectation, we found a sequence of such transitions in turbulent rotating Rayleigh-Bénard convection as the rotation rate was increased. This phenomenon was observed in cylindrical sampl...