The effect of Prandtl number on turbulent sheared thermal convection

Alexander Blass*, Pier Tabak, Roberto Verzicco, Richard J.A.M. Stevens, Detlef Lohse

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

In turbulent wall sheared thermal convection, there are three different flow regimes, depending on the relative relevance of thermal forcing and wall shear. In this paper, we report the results of direct numerical simulations of such sheared Rayleigh-Bénard convection, at fixed Rayleigh number, varying the wall Reynolds number in the range and Prandtl number, extending our prior work by Blass et al. (J. Fluid Mech., vol. 897, 2020, A22), where was kept constant at unity and the thermal forcing varied. We cover a wide span of bulk Richardson numbers and show that the Prandtl number strongly influences the morphology and dynamics of the flow structures. In particular, at fixed and, a high Prandtl number causes stronger momentum transport from the walls and therefore yields a greater impact of the wall shear on the flow structures, resulting in an increased effect of on the Nusselt number. Furthermore, we analyse the thermal and kinetic boundary layer thicknesses and relate their behaviour to the resulting flow regimes. For the largest shear rates and numbers, we observe the emergence of a Prandtl-von Kármán log layer, signalling the onset of turbulent dynamics in the boundary layer.

Original languageEnglish
Article numberA37
JournalJournal of fluid mechanics
Volume910
Early online date15 Jan 2021
DOIs
Publication statusPublished - 10 Mar 2021

Keywords

  • UT-Hybrid-D
  • Bénard convection
  • turbulent convection
  • atmospheric flows
  • Benard convection

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