Hamburg 2001 – scientific programme
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DY: Dynamik und Statistische Physik
DY 20: Ferrofluide I
DY 20.1: Talk
Tuesday, March 27, 2001, 09:30–09:45, S 5.5
The influence of shear and vorticity on the magnetization dynamics of ferrofluids — •Stefan Odenbach1 and Hanns Walter Müller2 — 1ZARM, Universität Bremen, Am Fallturm, 28359 Bremen — 2Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz
The magnetic relaxation process in ferrofluids is known to depend on the vorticity of the underlying flow. However, due to the broken isotropic symmetry of magnetized ferrofluids, shear (or elongational) flow components have recently been predicted to become
relevant as well. The degree of this extra-coupling is experimentally measured by a Taylor-Couette apparatus, which allows for a continuous transition form a solid rotation (pure vorticity) to a simple shear (vortical plus elongational flow). Therefore the fluid in the gap between the rotating cylinders is magnetized perpendicular to the axis of rotation. Measuring the magnetization component perpendicular to the field direction provides a magnetization signal depending on the vorticity of the flow. In contrast to classical descriptions of ferrofluid dynamics this component of magnetization depends on shear due to the mentioned effects of elongational flow. First experimental results for this problem will be presented.