Fractality of metal pad instability threshold in rectangular cells

Politis, Gerasimos; Priede, Jānis

doi:10.1017/jfm.2021.100

Cited by 5 publications

(2 citation statements)

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“…Significant progress on this issue has recently been made by Bouvard, Herreman & Moisy (2017) and Faltinsen & Timokha (2019). And third, the hydrodynamic similarity to the magnetohydrodynamic 'metal pad roll instability', a potential limiting factor in aluminium reduction cells and liquid-metal batteries (Weber et al 2017;Herreman et al 2019;Politis & Priede 2021), was utilised by Horstmann, Wylega & Weier (2019). We introduced a multilayer orbital sloshing experiment, allowing us to imitate the wave motion as it can arise from the metal pad roll instability.…”

Section: Introductionmentioning

confidence: 99%

Formation of spiral waves in cylindrical containers under orbital excitation

et al. 2021

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The lowest swirling wave mode arising in upright circular cylinders as a response to circular orbital excitation has been widely studied in the last decade, largely due to its high practical relevance for orbitally shaken bioreactors. Our recent theoretical study (Horstmann et al., J. Fluid Mech., vol. 891, 2020, A22) revealed a damping-induced symmetry breaking mechanism that can cause spiral wave structures manifested in the so far widely disregarded higher rotating wave modes. Building on this work, we develop a linear criterion describing the degree of spiralisation and classify different spiral regimes as a function of the most relevant dimensionless groups. The analysis suggests that high Bond numbers and shallow liquid layers favour the formation of coherent spiral waves. This result paved the way to find the predicted wave structures in our interfacial sloshing experiment. We present two sets of experiments, with different characteristic damping rates, verifying the formation of both coherent and overdamped spiral waves in conformity with the theoretical predictions.

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Section: Introductionmentioning

confidence: 99%

Formation of spiral waves in cylindrical containers under orbital excitation

et al. 2021

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“…In such cases the instability seems to arise from a degeneracy between two transverse fluid oscillation modes. Indeed, a more recent work [8] showed that for a battery with rectangular cross section there is actually a dense set of such instability points, such the fluid is easily rendered unstable any time the aspect ratio is equal to m/n, where m and n are odd numbers. The instability is dampened when the fluid has a finite viscosity, but when this viscosity is not too large the threshold value of the magnetic field or current density that produces the instability retains a jagged dependence on the aspect ratio.…”

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confidence: 99%

Liquid metal batteries and their magnetohydrodynamic instabilities

2022

Journal Club for Condensed Matter Physics

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Recommended with a Commentary by Brian Skinner, Ohio State UniversityLiquid metals are an old source of fascination in condensed matter physics. For example, understanding their electrical conductivity (even its order of magnitude) was a serious puzzle for many decades, since one cannot use Bloch's theorem in a setting with no periodic structure. (This puzzle was finally cracked in the 1960s -Ref. [1] by Ziman gives a very enjoyable overview.) Recent years have seen a mild revival of interest in liquid metals, with a focus on their mechanical properties [2]. For example, the surface tension of many liquid metals is altered enormously by the formation of an oxide layer on its surface, which presumably grows by the Cabrera-Mott mechanism [3]. (Briefly: an electron first quantumtunnels across the oxide layer from the bulk metal to bind to an oxygen atom on the surface, and then drags a metal ion across the oxide via the Coulomb attraction, so that the oxide thickness is tunneling-limited and grows logarithmically in time.) Consequently, the metal's surface tension can be strongly altered (and even brought to zero) by an applied voltage; Ref.[4] presents some fun experiments in which a spherical liquid metal droplet is reversibly turned into fractal shapes.The two recommended papers illustrate yet another reason why condensed matter physicists might consider reviving their interest in liquid metals. They concern the operation of a certain new type of battery made from liquid metals. The usefulness of these batteries turns out to be limited by a surprising magnetohydrodynamic instability.Before describing these papers, it is worth remarking on the general context that is driving research into new types of battery. The cost of energy generation through renewable sources (and solar panels in particular) has fallen so dramatically in the last decade that this cost is no longer the primary bottleneck for achieving an all-renewable energy grid [5]. A more significant bottleneck now is the cost and efficiency of energy storage. Efficient, large-scale energy storage is needed over a wide range of time scales, from seconds to months, in order

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