Jump rope vortex in liquid metal convection

Tobias Vogt; Susanne Horn; Alexander M Grannan; Jonathan M Aurnou

doi:10.1073/pnas.1812260115

Jump rope vortex in liquid metal convection

Proc Natl Acad Sci U S A. 2018 Dec 11;115(50):12674-12679. doi: 10.1073/pnas.1812260115. Epub 2018 Nov 21.

Authors

Tobias Vogt^{1

2}, Susanne Horn¹, Alexander M Grannan³, Jonathan M Aurnou³

Affiliations

¹ Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095; susannehorn@ucla.edu t.vogt@hzdr.de.
² Institute of Fluid Dynamics, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
³ Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095.

Abstract

Understanding large-scale circulations (LSCs) in turbulent convective systems is important for the study of stars, planets, and in many industrial applications. The canonical model of the LSC is quasi-planar with additional horizontal sloshing and torsional modes [Brown E, Ahlers G (2009) J Fluid Mech 638:383-400; Funfschilling D, Ahlers G (2004) Phys Rev Lett 92:194502; Xi HD et al. (2009) Phys Rev Lett 102:044503; Zhou Q et al. (2009) J Fluid Mech 630:367-390]. Using liquid gallium as the working fluid, we show, via coupled laboratory-numerical experiments in tanks with aspect ratios greater than unity ([Formula: see text]), that the LSC takes instead the form of a "jump rope vortex," a strongly 3D mode that periodically orbits around the tank following a motion much like a jump rope on a playground. Further experiments show that this jump rope flow also exists in more viscous fluids such as water, albeit with a far smaller signal. Thus, this jump rope mode is an essential component of the turbulent convection that underlies our observations of natural systems.

Keywords: coherent structures; liquid metals; thermal convection; turbulence.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't