July 1, 2019 Presentation Open Access

Schindler, Felix; Zürner, Till; Vogt, Tobias; Eckert, Sven; Schumacher, Jörg

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{
  "abstract": "<p>Lecture (Conference)</p>\n\n<p>11th PAMIR International Conference- Fundamental and Applied MHD July 1-5, 2019, Reims, EVEM France</p>\n\n<p>We are investigating turbulent Rayleigh-B&eacute;nard convection in liquid metal under the<br>\ninfluence of a vertical magnetic field. Utilizing a combination of thermocouple (TC) and<br>\nultrasound-Doppler-velocimetry (UDV) measurements gives us the possibility to directly<br>\ndetermine the temperature and velocity field, respectively. Further this gives us the<br>\npossibility to observe changes in the large-scale flow structure.<br>\nBy applying magnetic fields to the liquid metal convection, we quantified changes of heat<br>\nand momentum transport in the liquid metal alloy GaInSn. The experimental results of our<br>\nsetup agree well with theory findings and direct numerical simulations of the dynamics in<br>\nour convection cell. The requirement of large computing power at these parameters makes<br>\nit hard to simulate long-term dynamics with time scales from minutes to several hours. Thus<br>\nto investigate slow developing dynamics like sloshing, rotation, or deformation of the large-<br>\nscale flow structure model experiments are indispensable.<br>\nWe demonstrate the suppression of the convective flow by a vertical magnetic field in a<br>\ncylindrical cell of aspect ratio 1. In this setup Rayleigh numbers up to 6&middot;107 are<br>\ninvestigated. The flow structure at low Hartmann numbers is a single roll large scale<br>\ncirculation (LSC). Increasing the Hartmann number leads to a transition from the single-roll<br>\nLSC into a cell structure. An even stronger magnetic field supresses the flow in the center<br>\nof the cell completely and expels the flow to the side walls.<br>\nEven above the critical Hartmann numbers corresponding to the Chandrasekhar limit for<br>\nthe onset of magnetoconvection in a fluid layer without lateral boundaries we still observe<br>\nremarkable flows near the side walls. The destabilising effect of the non-conducting side<br>\nwalls was predicted by theory and simulations, and is here for the first time experimentally<br>\nconfirmed.</p>\n\n<p>&nbsp;</p>", 
  "issued": {
    "date-parts": [
      [
        2019, 
        7, 
        1
      ]
    ]
  }, 
  "version": "1.0", 
  "note": "Support by Deutsche Forschungsgemeinschaft with grants VO 2332/1-1 and SCHU 1410/29-1", 
  "language": "eng", 
  "author": [
    {
      "family": "Schindler, Felix"
    }, 
    {
      "family": "Z\u00fcrner, Till"
    }, 
    {
      "family": "Vogt, Tobias"
    }, 
    {
      "family": "Eckert, Sven"
    }, 
    {
      "family": "Schumacher, J\u00f6rg"
    }
  ], 
  "title": "Low Prandtl Number Rayleigh-B\u00e9nard Convection in a Vertical Magnetic Field", 
  "DOI": "10.14278/rodare.228", 
  "type": "speech", 
  "id": "228", 
  "publisher": "Rodare"
}