On the formation of Taylor-Gortler vortices in RMF-driven spin-up flows

This paper is concerned with a liquid metal flow driven by a rotating magnetic field inside a stationary cylinder. We consider especially the secondary meridional flow during the time when the fluid spins up from rest. The developing flow is investigated experimentally and by direct numerical simulations. The vertical profiles of the axial velocity are measured by means of the ultrasound Doppler velocimetry. Evolving instabilities in the form of Taylor-Gortler vortices have been observed just above the instability threshold (Ta >= 1.5. Ta(cr)). The rotational symmetry may survive over a distinct time even if a first Taylor-Gortler vortex pair has been formed as closed rings along the cylinder perimeter. The transition to a three-dimensional flow in the side layers results from the advection or a precession and splitting of the Taylor-Gortler vortex rings. The predictable behaviour of the Taylor-Gortler vortices disappears with increasing magnetic field strength. The numerical simulations agree very well with the flow measurements.