Pumping fluid by magnetic surface stress

Abstract

A magnetic field rotating on the free surface of a ferrofluid layer is shown to induce considerable fluid motion towards the direction the field is rolling. The measured flow velocity (i) increases with the square of the magnetic field amplitude, (ii) is proportional to the thickness of the fluid layer and (iii) has a maximum at a fluid specific frequency. The pumping speed can be estimated with a two-dimensional flow model. We compare the pumping performance of a magnetic fluid based on magnetite with the performance of a novel fluid based on cobalt. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.