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Vortex statistics in turbulent rotating convection.

Authors
  • Kunnen, R P J
  • Clercx, H J H
  • Geurts, B J
Type
Published Article
Journal
Physical Review E
Publisher
American Physical Society (APS)
Publication Date
Sep 01, 2010
Volume
82
Issue
3 Pt 2
Pages
36306–36306
Identifiers
PMID: 21230170
Source
Medline
License
Unknown

Abstract

The vortices emerging in rotating turbulent Rayleigh-Bénard convection in water at Rayleigh number Ra=6.0×10{8} are investigated using stereoscopic particle image velocimetry and by direct numerical simulation. The so-called Q criterion is used to detect the vortices from velocity fields. This criterion allows distinguishing vorticity- and strain-dominated regions in the flow by decomposing the velocity gradient tensor into symmetric and antisymmetric parts. Vortex densities, mean vortex radii and mean vortex circulations are calculated at two horizontal cross-sections of the cylindrical flow domain and at several rotation rates, described by the Taylor number which takes values between 3.0×10{8} and 7.7×10{10} . Separate statistics are calculated for cyclonic and anticyclonic vortices. Vortex densities and mean vortex radii are mostly independent of the Taylor number except very close to the bottom and top plates where more vortices are detected when the Taylor number is raised (rotation increases). The vortex population close to the plate consists mostly of cyclones while further into the bulk of the domain a similar amount of cyclones and anticyclones is found. The cyclonic vortices contain more circulation than the anticyclones. The same vortex analysis of the simulation results at additional vertical positions revealed that the vortices are formed in a boundary layer on the plate with a thickness of approximately two Ekman lengths.

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