Numerical and experimental investigation of helicity oscillations in liquid-metal convection

What is it about?

We present numerical and experimental results on helicity oscillations in a liquid-metal Rayleigh–Bénard convection cell with aspect ratio 0.5. The numerical simulations were carried out by means of the finite volume library OpenFOAM, and the experimental results were obtained by means of Contactless Inductive Flow Tomography (CIFT). Helicity oscillations occur not only during transitions of flow states with different roll numbers, but also during time intervals when the number of rolls remains constant and the Reynolds number is barely changing.

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Why is it important?

Helicity oscillations of the kink-type Tayler instability were recently discussed as a possible mechanism for synchronizing the solar dynamo by the tidal forces of the orbiting planets. Our observation that the helicity oscillations for the double-roll state exhibit characteristics remarkably similar to those associated with the Tayler instability points to a rather generic and universal character of this phenomenon.