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2 Publications

Transition in a weakly turbulent Rayleigh-Bénard convection exposed to a horizontal megnetic field

Vogt, T.; Yanagisawa, T.; Ishimi, W.; Tasaka, Y.; Eckert, S.


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 [1], [2]. 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 aim of this paper is to give a detailed description of the flow field, which is often considered as quasi 2D. In this paper we demonstrate the importance to take 3D flow effects into account in order to explain the observed flow features. The experiments are accompanied by direct numerical simulations. The comparison between the DNS and the flow measurements shows a very good agreement.

  • Contribution to proceedings
    16TH European Turbulence Conference, 21.-24.08.2017, Stockholm, Sweden
  • Lecture (Conference)
    16TH European Turbulence Conference, 21.-24.08.2017, Stockholm, Sweden


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