Experimental study of near-wall transport and structures in turbulent Rayleigh-Bénard convection

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The heat transfer between a solid surface and a surrounding fluid is a major process in many natural and technical flows. Although the basics of this process, generally referred to as convective heat transfer, have been studied intensively for more than hundred years, this process is not yet understood. New ideas like e.g. the analogy between the heat transport in Rayleigh-Bénard convection and the momentum transport in other turbulent flows may contribute to optimize the process of power generation, to improve the understanding and the predictability of the climate change or to increase the thermal comfort in interiors or passenger compartments. The “Barrel of Ilmenau” - a worldwide unique facility - permits measurements with unrivalled spatial and temporal resolution in highly turbulent and well-controlled convection. In collaboration with the partners in subproject RB-2 it should be studied and quantified, how coherent structures contribute to the convective heat transfer at the wall. Using imaging flow measurement techniques like Particle Image Velocimetry or Particle Tracking Velocimetry analogies between the heat transport in Rayleigh-Bénard convection and the momentum transport in Taylor-Couette and in pipe flow should be found. Since significantly higher transport rates are possible in the latter model experiments in the lab results obtained in the subprojects TC-1,2 and RS-1,2 might be transferred directly towards thermal convection at ultrahigh Rayleigh numbers.