Liquid Metal Flow near Magnetic Neutral Points

Abstract

In this study the possibility of employing a magnetic neutral point as an electromagnetic brake is explored. We consider flows along the tapering part of a magnetic neutral point rather than perpendicular to it as the problem then becomes very intractable for generalised flows (Alemany [a]). A full scale nonlinear approach to the problem has yet to be realised but the principal characteristics can be illustrated by considering a simpler model which yields analytic solutions. Pai [b] and Regirer [c] found expressions for the velocity profiles in both axisymmetric and two dimensional geometry. The fact that the flow rates in both dimensions are O(1/M ²) (M=Hartmann number) in the domain of large M suggests a means of controlling the mass flow rate. Intuition would anticipate jet-like structures for both geometries at large M but this is only found to be the case in 2D. The contrasting behaviour of the two flows results from the fact that curl(Lorentz force) equals zero in the core of the flow for large M and this has two differing effects in axisymmetry and 2D.