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SUMMARY:Boundary layers in high-Rayleigh-number turbulent convection - Jö
 rg Schumacher\, Technische Universität Ilmenau
DTSTART:20251024T150000Z
DTEND:20251024T160000Z
UID:TALK237964@talks.cam.ac.uk
CONTACT:Duncan Hewitt
DESCRIPTION:Turbulent convection processes are ubiquitous in nature and te
 chnology. We study the structure of thermal and viscous boundary layers in
  three-dimensional Rayleigh-Bénard convection\, a paradigm of these natur
 al flows\, for a range of Rayleigh numbers that spans 6 orders of magnitud
 e by means of direct numerical simulations. The configuration is a plane l
 ayer of aspect ratio 4 with periodic boundary conditions at the sides – 
 the configuration that comes close to the original configuration studied b
 y Lord Rayleigh and others. Velocity fluctuations dominate the near-wall r
 egions at all Rayleigh numbers. A global mean flow\, which is a prerequisi
 te for several theoretical models of turbulent heat transfer\, is practica
 lly absent. Rather\, the velocity field close to the wall can be decompose
 d into regions that are dominated by local\, differently oriented and tran
 sient shear motion with shear-free regions in between. Thermal plumes are 
 found to be organized in a self-similar hierarchical network\, which gets 
 coarser with increasing distance from the wall. The thermal boundary layer
 s are marginally stable\; the critical wavelength bounds the mean thermal 
 plume spacing in the hierarchical network for all Rayleigh numbers from be
 low. Our studies thus underline that the character of the near-wall layers
  in plane-layer Rayleigh-Bénard convection differs from those of canonica
 l wall-bounded shear flows.\n
LOCATION:MR2
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