Flow of two-dimensional liquid metal jet in a strong magnetic field.

Abstract

Steady, two-dimensional flow of a liquid metal jet pouring vertically down from a nozzle in the presence of crossed magnetic and electric fields has been investigated. The magnetic field is supposed to have a single component transverse to the flow. An asymptotic, high Hartmann number model has been used to study a combined effect of surface tension, nonuniform magnetic field, gravity and inertia. Relations have been obtained for a jet issuing from a duct, pouring into a draining duct, pouring from one duct into another, and that in a liquid bridge. The results show that the jet becomes thicker if the field increases along the flow and thinner if it decreases. It has also been shown that for gradually varying fields characteristic for the divertor region of both C-MOD and NSTX tokamaks, inertial effects are negligible for N > 10, where N is the interaction parameter. Thus, provided the jet remains stable, the inertialess flow model is expected to give good results even for relatively low magnetic fields and high jet velocity. Surface tension plays a crucial role in shaping the jet profile at the nozzle. Partial flooding of the nozzle walls is predicted. Finally, proposals have been made to investigate a possibility of using an axisymmetric curtain along the perimeter of the bottom of a tokamak as an alternative to the film- or jet-divertors, or to use a system of plane liquid metal sheets.