Regensburg 2016 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 57: Focus Session: Turbulence - From Pattern Formation to Stochastic Disorder
DY 57.11: Talk
Thursday, March 10, 2016, 18:00–18:15, H46
Large-scale structures in the temperature field in turbulent Rayleigh-Bénard convection — •Christian Resagk and Christian Kästner — TU Ilmenau, Ilmenau, Deutschland
Large-scale structures in temperature fields in turbulent convection is a less-studied phenomenon in large aspect ratio convection cells. Furthermore, the existence of superstructures in temperature fields is only known from direct numerical simulations and was not experimentally confirmed so far. Against this background we investigated large-scale circulation in water, applied to a Rayleigh-Bénard cell with large aspect ratio Γ=30 and Rayleigh numbers about Ra=104-106. We introduce temperature field measurements under the given conditions for the first time. Hence the major aim of this work was on the one hand checking the applicability of temperature field measurements and the accessible thermal resolution in turbulent flow by laser induced fluorescence (LIF) and thus the investigation of changing conditions from weak to strong turbulence, may yielding long term stabilization/oscillation of the convective flow. The Rayleigh number was controlled by adjusting the temperature gradient between hot bottom and cold top enclosure of the convection cell about ΔT=0-35 K. The convective flow of heat was monitored by particle imaging velocimetry (PIV) and compared with contact-less temperature field measurements by LIF, based on temperature induced fluorescence intensity variations of Rhodamin B added to the water. Both, PIV and LIF, were measured in 532 nm light sheet irradiation in the horizontal and vertical plane of the convective cell.