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Laboratory Experiments on Convective Entrainment Using a Saline Water Tank

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Abstract

Entrainment fluxes in a shear-free convective boundary layer have been measured with a saline water tank set-up. The experiments were targeted towards measuring the entrainment behaviour for medium to high Richardson numbers and use a two-layer design, i.e. two stacked non-stratified (neutral) layers with different densities. With laser induced fluorescence (LIF), the entrainment flux of a fluorescent dye is measured for bulk Richardson numbers in the range 30–260. It is proposed that a carefully chosen combination of top-down and bottom-up processes improves the accuracy of LIF-based entrainment observations. The observed entrainment fluxes are about an order of magnitude lower than reported for thermal water tanks: the derived buoyancy entrainment ratio, \(A\), is found to be \(A \approx 0.02\), which is to be compared with \(A\approx 0.25\) for a thermal convection tank (Deardorff et al., J Fluid Mech 100:41–64, 1980). An extensive discussion is devoted to the influence of the Reynolds and Prandtl numbers in laboratory experiments on entrainment.

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Acknowledgments

The authors thank Jos Verdoold, Thijs Heus, Esther Hagen, Jeroen Lebouille, Daniel Abrahams, Erwin de Beus and Rob Rodink for their efforts towards improving the set-up. One of us (MAJ) acknowledges research project CGL2006-12474 from the Spanish Government. Han van Dop, Peter Sullivan, Evgeni Fedorovich and Jeff Weil are gratefully acknowledged for contributing useful insights.

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Authors and Affiliations

  1. Atmospheric Physics Section, Department of Geoscience and Remote Sensing, Delft University of Technology, P.O. Box 5048, 2600 GA , Delft, The Netherlands

    Harmen J. J. Jonker

  2. Department of Global Change Research, Institut Mediterrani d’Estudis Avançats, IMEDEA (CSIC-UIB), Miquel Marquès 21, 07190 , Esporles (Illes Balears), Spain

    Maria A. Jiménez

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  1. Harmen J. J. Jonker
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  2. Maria A. Jiménez
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Correspondence to Harmen J. J. Jonker.

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Jonker, H.J.J., Jiménez, M.A. Laboratory Experiments on Convective Entrainment Using a Saline Water Tank. Boundary-Layer Meteorol 151, 479–500 (2014). https://doi.org/10.1007/s10546-014-9909-3

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