Lorentz force velocimetry with a small permanent magnet

In this paper, we propose an experimental methodology for the measurement of Lorentz forces acting on a small permanent magnet when exposed to the flow of an electrically conducting fluid. The present measurements are considerably more challenging than previous global flow measurements since they require accurate force measurements in the range of micro-newtons. To this end, we experimentally and numerically evaluate the total Lorentz force acting on a 1cm3 cubic permanent magnet that is exposed to a liquid metal flow in a straight rectangular duct with non-magnetic and electrically insulating walls. Parametric analyses are performed at different flow velocities and different relative magnet positions. High resolution force measurements are performed in a liquid metal channel filled with the eutectic alloy GaInSn. In spite of the simplified nature of the numerical approach the numerical results agree with the experiments. Hence the present results demonstrate the applicability of small magnet systems to LFV.