Viscous boundary layers in turbulent Rayleigh-Bénard convection

Highly resolved local velocity profiles inside the boundary layers in turbulent Rayleigh-Bénard convection in air are presented and discussed. The present work makes progress to our work in the past (see du Puits & Resagk, 2007) that our actual set-up permits the measurement of the wall-normal velocity component w up to a distance of 200 mm away from the wall. All component profiles were performed in a cylindrical box with an aspect ratio Γ = 1, a Prandtl number Pr = 0.7 and Rayleigh numbers Ra = 3 × 10 9 , Ra = 3 × 10 10 . We compare the experimental results with numerics at Ra = 3 × 10 10 directly. We found that the profiles of mean velocity from both experiments and numerics collapse very well with each other and both of the mean horizontal velocity profiles differ from the laminar Blasius prediction at the boundary layer. The wall-normal mean velocity at the central window tends to zero in both experiment and numerics.