Vortex plume distribution in confined turbulent rotating convection

¹ Fluid Dynamics Laboratory, Department of Applied Physics and J. M. Burgers Center for Fluid Dynamics, Eindhoven University of Technology - P.O. Box 513, 5600 MB Eindhoven, The Netherlands, EU
² Department of Applied Mathematics and J.M. Burgers Center for Fluid Dynamics, University of Twente P.O. Box 217, 7500 AE Enschede, The Netherlands, EU

^(a) r.p.j.kunnen@tue.nl

Received: 17 September 2013
Accepted: 6 December 2013

Abstract

Vortical columns are key features of rapidly rotating turbulent Rayleigh-Bénard convection. In this work we probe the structure of the sidewall boundary layers experimentally and show how they affect the spatial vortex distribution in a cylindrical cell. The cell has a diameter-to-height aspect ratio and is operated at Rayleigh number and Prandtl number 6.4. The vortices are detected using particle image velocimetry. We find that for inverse Rossby numbers (expressing the rotation rate in a dimensionless form) the sidewall boundary layer exhibits a rotation-dependent thickness and a characteristic radial profile in the root-mean-square azimuthal velocity with two peaks rather than a single peak typical for the non-rotating case. These properties point to Stewartson-type boundary layers, which can actually cover most of the domain for rotation rates just above the transition point. A zonal ordering of vortices into two azimuthal bands at moderate rotation rates can be attributed to the sidewall boundary layer. Additionally, we present experimental confirmation of the tendency of like-signed vortices to cluster on opposite sides of the cylinder for . At higher rotation rates and away from the sidewall the vortices are nearly uniformly distributed.