Bert Reimann

Fluid pumped by magnetic stress

A magnetic field rotating on the free surface of a ferrofluid layer is shown to induce considerable fluid motion toward 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 driving frequency of about 3kHz. The pumping speed can be estimated with a two-dimensional flow model.

Pumping fluid by magnetic surface stress

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.

Standing twin peaks due to non–monotonic dispersion of Faraday waves

Abstract We report on a Faraday experiment with magnetic fluid in a DC magnetic field, which is driven externally by accelerative modulation. A novel pattern of standing twin peaks is found. It has its origin in the simultaneous excitation of two different wave numbers in the non-monotonic regime of the dispersion relation.