Heat transport in turbulent Rayleigh-Bénard convection for Pr ≃ 0.8 and Ra ≲ 1015

Abstract

We report experimental results for the heat transport, as expressed by the Nusselt number Nu, by turbulent Rayleigh-Bénard convection in a cylindrical sample of aspect ratio Γ = D/L = 0.50 (D = 1.12 m is the diameter and L = 2.24 m the height). The measurements are for the Rayleigh-number range 1012 ≲ Ra ≲ 1015 and for a Prandtl number Pr ≃ 0.86. At these large Ra the results were exceptionally sensitive to details of the experiment. Near Ra = 1015 the Nusselt number could be caused to vary over the range 3500 ≲ Nu ≲ 5800 by minor changes in the apparatus or operating procedure.