Flow organization and heat transfer in turbulent wall sheared thermal convection

Alexander Blass*, Xiaojue Zhu, Roberto Verzicco, Detlef Lohse*, Richard J.A.M. Stevens*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

We perform direct numerical simulations of wall sheared Rayleigh-Bénard convection for Rayleigh numbers up to, Prandtl number unity and wall shear Reynolds numbers up to. Using the Monin-Obukhov length we observe the presence of three different flow states, a buoyancy dominated regime (; with the thermal boundary layer thickness), a transitional regime (; with the height of the domain) and a shear dominated regime (). In the buoyancy dominated regime, the flow dynamics is similar to that of turbulent thermal convection. The transitional regime is characterized by rolls that are increasingly elongated with increasing shear. The flow in the shear dominated regime consists of very large-scale meandering rolls, similar to the ones found in conventional Couette flow. As a consequence of these different flow regimes, for fixed and with increasing shear, the heat transfer first decreases, due to the breakup of the thermal rolls, and then increases at the beginning of the shear dominated regime. In the shear dominated regime the Nusselt number effectively scales as with, while we find in the buoyancy dominated regime. In the transitional regime, the effective scaling exponent is 1/3$]]>, but the temperature and velocity profiles in this regime are not logarithmic yet, thus indicating transient dynamics and not the ultimate regime of thermal convection.

Original languageEnglish
Article numberA22
JournalJournal of fluid mechanics
Volume897
Early online date17 Jun 2020
DOIs
Publication statusE-pub ahead of print/First online - 17 Jun 2020

Keywords

  • UT-Hybrid-D
  • heat transfer
  • Rayleigh-Bénard convection
  • turbulent convection
  • Couette flow

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