Controlling the dimensionality of low-Rm MHD turbulence experimentally

TL;DR

This study presents an experimental setup that allows precise control over the dimensionality of turbulence in liquid metal under high magnetic fields, enabling exploration from three-dimensional to quasi two-dimensional turbulence regimes.

Contribution

The paper introduces a novel experimental apparatus that can tune turbulence dimensionality via a single parameter, advancing the study of MHD turbulence.

Findings

Dimensionality of turbulence is governed by the ratio lz(li)/h.

The apparatus can switch turbulence between 3D and quasi 2D regimes.

High-resolution measurements of inertial range features are achieved.

Abstract

This paper introduces an experimental apparatus, which drives turbulence electrically in a liquid metal pervaded by a high magnetic field. Unlike past magnetohydrodynamic (MHD) setups involving a shallow confinement, the experiment presented here drives turbulence whose dimensionality can be set anywhere between three-dimensional and quasi two-dimensional. In particular, we show that the dimensionality and componentality of the turbulence thus generated are in fact completely fixed by the single parameter lz(li)/h, which quantifies the competition between the solenoidal component of the Lorentz force and inertia acting on a turbulent structure of the size of the forcing scale li. This parameter is fully tunable thanks to the three operating settings at hand: the injection scale, the intensity of the electric forcing and the magnitude of the magnetic field. Thanks to the very high number of measuring probes and fast acquisition rate implemented in this experiment, it is possible to reliably measure the finest features of the inertial range on a scale-wise basis.

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