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SUMMARY:Large-scale flow structures in turbulent Rayleigh-Bénard convecti
 on: Dynamical origin\, formation\, and role in material transport - Philip
 p Vieweg
DTSTART:20240429T113000Z
DTEND:20240429T123000Z
UID:TALK216511@talks.cam.ac.uk
CONTACT:Prof. John R. Taylor
DESCRIPTION:The interplay of gravity with mass density inhomogeneities int
 roduces natural (thermal) convection and represents the essential mechanis
 m by which heat is transported in natural flows. Simultaneously\, natural 
 flows are often far more extended in the horizontal direction than in the 
 vertical one. Motivated by these two observations and the various geo- and
  astrophysical applications (e.g. the solar convection zone)\, 3-dimension
 al Rayleigh-Bénard convection as the paradigm of thermal convection has b
 een studied.\nThis talk will cover some recent results from studying the i
 mpact of thermal (and mechanical) boundary conditions on large-scale flow 
 structures in Rayleigh-Bénard convection by means of direct numerical sim
 ulations. It will be shown that thermal boundary conditions are crucial to
  the formation of long-living large-scale (turbulent) flow structures. In 
 particular\, a slow transient aggregation process — that only stops once
  the horizontal extent of the domain is reached — can be found once the 
 fluid layer is subjected to Neumann-type constant heat flux boundary condi
 tions. As a result\, the temperature field in the domain is separated into
  one extended hot and another extended cold region. We trace this mechanis
 m of self-organisation of flow structures back to secondary instabilities 
 as well as an inverse cascade in spectral space. The talk will finish with
  a brief overview of our work on the identification of those large-scale f
 low structures by the use of unsupervised machine learning based on Lagran
 gian particle data.
LOCATION:MR5\, CMS
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