The Geostrophic Regime of Rotating Rayleigh-Benard Convection: Heat Transport and Local Properties

Robert Ecke
Los Alamos National Laboratory

Rotation influences thermal convection in a multitude of ways: from changing the mechanism of pattern formation near onset for weak rotation to enhancing heat transport through Ekman pumping in turbulent thermal boundary layers. Recently there has been significant interest in the geostrophic range of rotating convection where, except in the cores of spatially localized vorticies and near solid boundaries, Coriolis forces balance pressure gradients. This geostrophic range occurs when rotation is dominant over thermal buoyancy, i.e., when the Rossby number is small. I will describe recent experimental work on rotating convection in cryogenic helium and in water. In helium gas we explore the heat transport dependence on Rayleigh and Ekman numbers in a new range of those parameters compared with previous work. In water we have made local measurements of vertical heat transport and characterized the relative contribution of convective Taylor columns to overall global heat transport. Through comparison of these experimental results with numerical simulations and theory of rotating convection by others, a reasonable description of the geostrophic thermal convection regime is emerging.

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