Free-fall velocities and heat transport enhancement in liquid metal magneto-convection. (17th March 2021)

• Record Type: Journal Article
• Authors: Vogt, Tobias; Yang, Juan-Cheng; Schindler, Felix; Eckert, Sven
• Is Part Of: Journal of fluid mechanics. Volume 915(2021)
• Publication Date: 2021-03-17
• Subjects: Bénard convection, -- magneto convection, -- MHD turbulence; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2021.108
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: Abstract : In geo- and astrophysics, low Prandtl number convective flows often interact with magnetic fields. Although a static magnetic field acts as a stabilizing force on such flow fields, we find that self-organized convective flow structures reach an optimal state where the heat transport significantly increases and convective velocities reach the theoretical free-fall limit, i.e. the maximum possible velocity a fluid parcel can achieve when its potential buoyant energy is fully converted into kinetic energy. Our measurements show that the application of a static magnetic field leads to an anisotropic, highly ordered flow structure and a decrease of the turbulent fluctuations. When the magnetic field strength is increased beyond the optimum state, Hartmann braking becomes dominant and leads to a reduction of the heat and momentum transport. The results are relevant for the understanding of magneto-hydrodynamic convective flows in planetary cores and stellar interiors in regions with strong toroidal magnetic fields oriented perpendicular to temperature gradients.