6. 11. 2019

Michal Macek (ÚPT AVČR Brno):
Transport of heat by classical and quantum turbulent flows in cryogenic helium-4

Abstract:

The chaotic, yet evidently partly organized nature of turbulent flows has
puzzled and fascinated people long into history. Nevertheless turbulence still
remains an open scientific and engineering problem, and perhaps not less
importantly a source of inspiration in arts.

We will overview different turbulent flows driven by and also transporting
heat, that can be studied in cryogenic laboratories, pointing out that helium
4He at low temperatures provides an excellent environment to study many of them
in controlled laboratory conditions: Thanks to scaling propeties of the
hydrodynamic equations, (almost) tabletop experiments using 4He provide
reasonably simple models of large-scale flows in Nature, which still represent
formidable challenges for numerical simulations.

We will focus on experiments on classical turbulence in Rayleigh-Benard
convection, studied in the cryogenic laboratories at ISI Brno, especially on
the attempts to reach the so-called "ultimate" or asymptotic regime of
turbulent convection, theoretically predicted by Kraichnan in 1960s yet
experimentally still raising controversy. Understanding this regime better may
improve modelling of flows e.g. in Earth's atmosphere, oceans, the solar
mantle, etc.

We will briefly touch experiments on quantum turbulence, studied in our partner
laboratories in Prague (group of prof. L. Skrbek) and Florida (group of prof.
W. Guo), and outline possible connections between the two types of turbulence.