What is it about?
The instability mechanism is based on the standing gravity wave modification due to the electric current redistribution. The electric current density in the liquid increases above the wave crests, resulting in a high density horizontal currents in the shallow liquid metal layers. In the presence of a vertical magnetic field the electromagnetic force excites another standing wave mode orthogonal to the initial perturbation. The new wave mode is coupled to the original mode, and the oscillation frequency is shifted. The frequency shift increases with the rise of the magnetic field until at a critical value, when the two orthogonal wave frequencies coincide, at which an exponential growth of the amplitude indicates the onset of instability.
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Why is it important?
Liquid metal batteries are possible candidates for large scale electrical energy storage offering a possible breakthrough of intermittent wind and solar energy exploitation.
Perspectives
The presented linear theory derivation focused on the ability to obtain some analytical results for the stability, while intentionally avoiding the more realistic set-up when the electric current supply at the top and bottom collectors is non-uniform. The simplification permitted us to avoid the inclusion of the horizontal velocity circulation effects on the magneto-hydrodynamic stability. In the general case the curl of electromagnetic force is not identically zero, leading to the horizontal velocity circulation which can affect the interface deformation. The full nonlinear interaction remains the subject for a future research.
Valdis Bojarevics
University of Greenwich
Read the Original
This page is a summary of: Magnetohydrodynamic stability of large scale liquid metal batteries, Journal of Fluid Mechanics, August 2018, Cambridge University Press,
DOI: 10.1017/jfm.2018.482.
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