Shishkina Olga, Lohse Detlef
<a href="https://ror.org/0087djs12">Max Planck Institute for Dynamics and Self-Organization</a>, 37077 Göttingen, Germany.
Physics of Fluids Department, J.M. Burgers Center for Fluid Dynamics, and Max Planck-University of Twente Center for Complex Fluid Dynamics; Faculty of Science and Technology, <a href="https://ror.org/006hf6230">University of Twente</a>, Enschede, The Netherlands.
Phys Rev Lett. 2024 Oct 4;133(14):144001. doi: 10.1103/PhysRevLett.133.144001.
We offer a new model for the heat transfer and the turbulence intensity in strongly driven Rayleigh-Bénard 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. [Upper bounds on Nusselt number at finite Prandtl number, J. Differ. Equations 260, 3860 (2016).JDEQAK0022-039610.1016/j.jde.2015.10.051] 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-Rayleigh 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-Rayleigh datasets, though at different Rayleigh numbers, as to be expected for a non-normal-nonlinear instability.
