Presentation Open Access
Schindler, Felix; Zürner, Till; Vogt, Tobias; Eckert, Sven; Schumacher, Jörg
{ "author": [ { "family": "Schindler, Felix" }, { "family": "Z\u00fcrner, Till" }, { "family": "Vogt, Tobias" }, { "family": "Eckert, Sven" }, { "family": "Schumacher, J\u00f6rg" } ], "note": "Support by Deutsche Forschungsgemeinschaft with grants VO 2332/1-1 and SCHU 1410/29-1", "id": "228", "DOI": "10.14278/rodare.228", "type": "speech", "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-Bénard 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 6·107 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> </p>", "publisher": "Rodare", "version": "1.0", "language": "eng", "issued": { "date-parts": [ [ 2019, 7, 1 ] ] }, "title": "Low Prandtl Number Rayleigh-B\u00e9nard Convection in a Vertical Magnetic Field" }
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