Regensburg 2019 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 5: Convection

DY 5.5: Vortrag

Montag, 1. April 2019, 11:15–11:30, H3

The evolution of the large-scale flow in magnetoconvection — •Till Zürner¹, Felix Schindler², Tobias Vogt², Sven Eckert², and Jörg Schumacher¹ — ¹Institute of Thermodynamics and Fluid Mechanics, Technische Universität Ilmenau, Postfach 100565, 98684 Ilmenau — ²Department Magnetohydrodynamics, Institute of Fluid Dynamics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden, Germany

We investigate the effect of a vertical magnetic field on the flow properties of turbulent Rayleigh-Bénard convection. The large-scale flow of a low-Prandtl number liquid metal alloy in a cylindrical convection cell of aspect ratio 1 is reconstructed by a combination of temperature and direct velocity measurements, using ultrasound Doppler velocimetry (UDV). In accordance to theory and simulations the flow strength is reduced by the induced Lorentz forces. With increasing magnetic field strength a transition from the turbulent one-roll large-scale circulation to a weakly non-linear cell-like structure is observed. Increasing the field strength even further finally supresses the flow in the centre of the cell almost completely. However, even at such high fields significant flows can still be observed near the side walls of the cell, far above the critical Hartmann number of the Chandrasekhar limit for the onset of magnetoconvection for a fluid layer without lateral boundaries. This destabilising effect of non-conducting side walls was predicted by theory and simulations, and is here confirmed by experiments for the first time.