Experimental evidence for the boundary zonal flow in rotating Rayleigh-Benard convection

Abstract

We report on the presence of the boundary zonal flow in rotating Rayleigh-Benard convection evidenced by two-dimensional particle image velocimetry. Experiments were conducted in a cylindrical cell of aspect ratio between its diameter (D) and height (H) of G=D/H=1. As the working fluid we used various mixtures of water and glycerol, leading to Prandtl numbers in the range 6.6<Pr<75. The horizontal velocity components were measured at a horizontal cross-section at half height. The Rayleigh numbers were in the range 10e8 < Ra < 6.3e9. The effect of rotation is quantified by the Ekman number which was between 1.5e-5<Ek< 1.2e-3 in our experiment. With our results we show the first direct measurements of the boundary zonal flow - BZF that develops near the sidewall and was recently discovered in numerical simulations as well as in sparse and localized temperature measurements. We analyse the thickness of the BZF as well as its maximal velocity as function of Pr, Ra, and Ek, and compare these results with previous DNS results.