Thermal turbulence in cryogenic helium gas

Several recent experiments have utilized cryogenic helium gas in order to generate high levels of thermal turbulence within a layer of gas heated from below. As the principal control parameter for the fluid turbulence depends strongly on the layer height, this has typically been made as large as feasible, while the lateral dimensions have been kept of the same dimension or smaller for practical reasons. While we continue to learn many important things from small aspect ratio experiments, implications and limitations of this lateral confinement are discussed, given our current understanding of the nature of large scale recirculating flows in developed turbulent convection. (C) 2003 Elsevier Science B.V. All rights reserved.