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DY: Fachverband Dynamik und Statistische Physik
DY 5: Convection
DY 5.3: Talk
Monday, April 1, 2019, 10:45–11:00, H3
Experimental analysis of superstructures in large-aspect-ratio Rayleigh Bénard convection — Christian Kästner, •Christian Resagk, and Jörg Schumacher — Institute of Thermodynamics and Fluid Mechanics, TU Ilmenau, Ilmenau
We report about measurement and analysis of horizontal velocity fields in a square Rayleigh-Bénard convection cell at an aspect ratio Gamma = 10 with compressed air and sulfur hexafluoride as working fluid. 2D3C horizontal cuts through the convective flow were obtained from stereoscopic particle image velocimetry (SPIV) measurements. Optical access for laser light sheet and PIV cameras was provided by transparent side-walls and a transparent heating plate. The application of a transparent heating plate, a glass plate coated with a transparent and electrically conductive metal oxide (TCO), allowed first time experimental observation of horizontal velocity fields in turbulent thermal convection at large aspect ratio. The horizontal cuts were taken in mid-plane of the convection cell and below the cooling plate at a Rayleigh number ranging from Ra = 104 - 107. Spatial and transient analysis of the velocity fields revealed superstructures, steadily increasing in size with increasing Rayleigh number. Hence the present experimental approach and results provide further insights into large-scale coherent flow pattern formation in turbulent thermal convection.