TY - JOUR
T1 - Rotating turbulent thermal convection at very large Rayleigh numbers
AU - Wedi, Marcel
AU - Van Gils, Dennis P.M.
AU - Bodenschatz, Eberhard
AU - Weiss, Stephan
PY - 2021/4/10
Y1 - 2021/4/10
N2 - We report on turbulent thermal convection experiments in a rotating cylinder with a diameter () to height () aspect ratio of. Using nitrogen and pressurised sulphur hexafluoride we cover Rayleigh numbers (Ra) from to at Prandtl numbers. For these Ra we measure the global vertical heat flux (i.e. the Nusselt number - Nu), as well as statistical quantities of local temperature measurements, as a function of the rotation rate, i.e. the inverse Rossby number - 1/Ro. In contrast to measurements in fluids with a higher Pr we do not find a heat transport enhancement, but only a decrease of Nu with increasing 1/Ro. When normalised with Nu(0) for the non-rotating system, data for all different Ra collapse and, for sufficiently large 1/Ro, follow a power law. Furthermore, we find that both the heat transport and the temperature field qualitatively change at rotation rates and. We interpret the first transition at as change from a large-scale circulation roll to the recently discovered boundary zonal flow (BZF). The second transition at rotation rate is not associated with a change of the flow morphology, but is rather the rotation rate for which the BZF is at its maximum. For faster rotation the vertical transport of warm and cold fluid near the sidewall within the BZF decreases and hence so does Nu.
AB - We report on turbulent thermal convection experiments in a rotating cylinder with a diameter () to height () aspect ratio of. Using nitrogen and pressurised sulphur hexafluoride we cover Rayleigh numbers (Ra) from to at Prandtl numbers. For these Ra we measure the global vertical heat flux (i.e. the Nusselt number - Nu), as well as statistical quantities of local temperature measurements, as a function of the rotation rate, i.e. the inverse Rossby number - 1/Ro. In contrast to measurements in fluids with a higher Pr we do not find a heat transport enhancement, but only a decrease of Nu with increasing 1/Ro. When normalised with Nu(0) for the non-rotating system, data for all different Ra collapse and, for sufficiently large 1/Ro, follow a power law. Furthermore, we find that both the heat transport and the temperature field qualitatively change at rotation rates and. We interpret the first transition at as change from a large-scale circulation roll to the recently discovered boundary zonal flow (BZF). The second transition at rotation rate is not associated with a change of the flow morphology, but is rather the rotation rate for which the BZF is at its maximum. For faster rotation the vertical transport of warm and cold fluid near the sidewall within the BZF decreases and hence so does Nu.
KW - Bénard convection
KW - Rotating turbulence
KW - Turbulent convection
KW - Benard convection
KW - UT-Hybrid-D
UR - http://www.scopus.com/inward/record.url?scp=85098416948&partnerID=8YFLogxK
U2 - 10.1017/jfm.2020.1149
DO - 10.1017/jfm.2020.1149
M3 - Article
AN - SCOPUS:85098416948
SN - 0022-1120
VL - 912
JO - Journal of fluid mechanics
JF - Journal of fluid mechanics
M1 - A30
ER -