Contact

Dr. Tom Weier
Magnetohydrodynamics
t.weierAthzdr.de
Phone: +49 351 260 - 2226, 2013
Fax: +49 351 260 - 12226, 12013, 2007

Gerrit Maik Horstmann
Magnetohydrodynamics
g.horstmannAthzdr.de
Phone: +49 351 260 - 3117

Eye catcher

Interfacial instabilities

The metal pad roll, or sloshing instability is a long-wave deformation of an interface (fig. 1). It is well known from aluminium reduction cells, where it limits the possible minimal thickness of the electrolyte layer. The instability is caused by an interaction of a vertical magnetic field with horizontal cell currents. The latter result directly from the deformed interface (fig. 2). A vertical magnetic field may originate from external feeding lines or may just be the Earth magnetic field.

   Metal pad roll instability    Compensation current metal pad roll instability
Fig. 1: Metal pad roll instability in a liquid metal battery. FIg. 2: Compensation current due to the interface inclination.

The metal pad roll instability may potentially short-circut a liquid metal battery. It must therefore be avoided. Especially shallow cells with large cell currents and large vertical stray fields are susceptible to the sloshing instability. The density jumps between the single phases should be as large as possible to avoid sloshing. At HZDR we use potential theory, numerical simulation and experiments in order to better understand the onset and relevance of metal pad rolling for large scale liquid metal batteries. We further study the coupling of both interfaces in the battery. Depending on the density ratios and the surface tension, very different wave shapes can appear (fig. 3).

   Coupling top    Coupling bottom
   Tilt instability    Bulge instability
Fig. 3: Different instabilites of the two interfaces in a liquid metal battery.

Publications


Contact

Dr. Tom Weier
Magnetohydrodynamics
t.weierAthzdr.de
Phone: +49 351 260 - 2226, 2013
Fax: +49 351 260 - 12226, 12013, 2007

Gerrit Maik Horstmann
Magnetohydrodynamics
g.horstmannAthzdr.de
Phone: +49 351 260 - 3117