Sheared boundary layers in turbulent Rayleigh-Bénard convection

Abstract

Thermal boundary layers in turbulent Rayleigh-Bénard convection are studied experimentally using a novel system in which the convecting fluid is sheared from below with a flowing layer of mercury. Oscillatory shear substantially alters the spatial structure and frequency of the eruptions, with minimal effect on the heat flux (<5%). The temperature probability distribution function (PDF) just above the lower boundary layer changes from Gaussian to exponential, without significant changes in the interior PDF. Implications for theories of ‘‘hard’’ turbulence are discussed.