Dresden 2017 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 16: Focus: Fundamental aspects of turbulent convection
DY 16.4: Vortrag
Dienstag, 21. März 2017, 10:30–10:45, ZEU 118
The effect of a horizontal magnetic field on weakly turbulent Rayleigh-Benard convection — Vogt Tobias1, Ishimi Wataru2, Tasaka Yuji2, Yanagisawa Takatoshi3, and •Eckert Sven1 — 1Helmholtz Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany — 2Laboratory for Flow Control, Hokkaido University, Sapporo, Japan — 3Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
MHD Rayleigh-Bénard convection was studied experimentally using the eutectic metal alloy GaInSn inside a box having a square horizontal cross section and an aspect ratio of length/height = 5/1. Systematic flow measurements were performed by means of ultrasound Doppler velocimetry that can capture time variations of instantaneous velocity profiles. Applying a horizontal magnetic field organizes the convective motion into a flow pattern of quasi-two dimensional rolls arranged parallel to the magnetic field. If the Rayleigh number (Ra) is increased over a certain threshold Ra/Q, whereby Q is the Chandrasekhar number, the convection flow undergoes a transition to turbulence. Besides the primary convection rolls the flow measurements reveal regular flow oscillations arising from 2D and 3D deformations of the rolls, Ekman-pumping induced flow as well as smaller side vortices that develop around the convection rolls. The experiments are accompanied by direct numerical simulations. The comparison between the DNS and the flow measurements shows a very good agreement.