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arXiv · 2407.16573

Ultimate regime of Rayleigh-Benard turbulence: Sub-regimes and their scaling relations for Nu vs. Ra and Pr

Olga Shishkina·Detlef Lohse
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Abstract

We offer a new model for the heat transfer and the turbulence intensity in strongly driven Rayleigh-Benard turbulence (the so-called ultimate regime), which in contrast to hitherto models is consistent with the new mathematically exact heat transfer upper bound of Choffrut et al. [J. Differential Equations 260, 3860 (2016)] and thus enables extrapolations of the heat transfer to geo- and astrophysical flows. The model distinguishes between four subregimes of the ultimate regime and well describes the measured heat transfer in various large-Ra experiments. In this new representation, which properly accounts for the Prandtl number dependence, the onset to the ultimate regime is seen in all available large-Ra data sets, though at different Rayleigh numbers, as to be expected for a non-normal-nonlinear instability.

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Olga Shishkina, Detlef Lohse. 2024-07-23. Ultimate regime of Rayleigh-Benard turbulence: Sub-regimes and their scaling relations for Nu vs. Ra and Pr. https://arxiv.org/abs/2407.16573

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