TY - JOUR
T1 - The effect of Prandtl number on turbulent sheared thermal convection
AU - Blass, Alexander
AU - Tabak, Pier
AU - Verzicco, Roberto
AU - Stevens, Richard J.A.M.
AU - Lohse, Detlef
N1 - Cambridge UP deal
PY - 2021/3/10
Y1 - 2021/3/10
N2 - 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.
AB - 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.
KW - UT-Hybrid-D
KW - Bénard convection
KW - turbulent convection
KW - atmospheric flows
KW - Benard convection
UR - http://www.scopus.com/inward/record.url?scp=85099365116&partnerID=8YFLogxK
U2 - 10.1017/jfm.2020.1019
DO - 10.1017/jfm.2020.1019
M3 - Article
AN - SCOPUS:85099365116
SN - 0022-1120
VL - 910
JO - Journal of fluid mechanics
JF - Journal of fluid mechanics
M1 - A37
ER -