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 57.13: Talk

Thursday, March 10, 2016, 18:30–18:45, H46

Global flow modes in turbulent Rayleigh-Bénard convection — •Robert Kaiser and Ronald du Puits — Institute of Thermodynamics and Fluid Mechanics, Technische Universität Ilmenau, Postfach 10 05 65, Ilmenau 98694, Germany

The modes of the global flow structure inside a Rayleigh-Bénard convection cell are analysed by time resolved local wall heat flux data. The measurements were performed at the heating plate of the large scale convection facility, called the Barrel of Ilmenau, using infrared thermography. The experimental data reveals a fundamental change of the heat transport processes between an aspect ratio 1<G<3, where the large scale vortex splits into two smaller vortices. In 2007 du Puits et al. measured profiles of the velocity and temperature in the boundary layer below the cooling plate at various aspect ratios G in the Barrel of Ilmenau. Between 1.47<G<1.89, the maximum velocity falls down by 20%. Thus, the critical aspect ratio Gc of the change in the modes of the global flow structure was estimated by a linear interpolation at Gc=1.68. We re-evaluated this value by calculating the average life time of the one-vortex-state and the two-vortex-state between 1<G<3. The new Gc=1.65 states more precisely the change in the global flow structure in turbulent Rayleigh-Bénard convection.