Spin-up of the vortex flow of liquid metal in a thin layer placed in an alternating magnetic field

The paper studies the transient nonequilibrium modes of a vortex flow in a thin liquid metal layer. The flow is caused by electromagnetic forces generated by the interaction of an alternating magnetic field and electric current induced by it. The most stable variant of the flow, in the form of two large-scale vortices, is studied. In this instance, the region where the alternating magnetic field is generated is situated in close proximity to the edge of the longer side of the rectangular liquid metal layer. Upon activation of the inductor, the flow evolves from rest to some equilibrium state. Conversely, upon deactivation, the flow diminishes. The study is conducted on a gallium eutectic alloy by means of an ultrasonic Doppler velocimeter. Two parameters determining the intensity of the force action are varied: the strength and frequency of the electric current flowing through the inductor windings. The durations of flow evolution and decay depending on the varying process parameters are evaluated. Vortex flow studies can be useful for designing MHD pumps and for stirring liquid metals.