Regensburg 2007 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 26: Ferrofluids / Liquid crystals

DY 26.9: Talk

Thursday, March 29, 2007, 12:30–12:45, H3

Parametric modulation of thermal and thermomagnetic convection in magnetic fluids — •Harald Engler and Stefan Odenbach — Lehrstuhl für Magnetofluiddynamik, Technische Universität Dresden, 01062 Dresden

Former theoretical investigations of the behaviour of thermal convection under the influence of a time modulated driving force have shown that the threshold where heat flux converts from diffusion to convective flow depends on the frequency of the driving force. However experimental setups to generate thermal convection with a time modulated driving force fails due to the immense technical problems. Recent research activities on heat and mass transfer phenomena in ferrofluids - superparametric suspensions of magnetic particles with an average diameter of 10 nm in appropriate carrier liquids - are focused on the influence of time modulated driving force on the critical temperature difference of thermomagnetic convection. The driving force in convection in ferrofluids, so called thermomagnetic convection, depends on temperature difference, geometric boundary and the additional magnetic force provided by an external magnetic field. A time modulated magnetic field that provides the required time dependent driving force with frequencies in the order of 1 Hz can easily be realized. The experimental setup designed for the investigation of thermomagnetic convection under the influence of time varying magnetic force as well as the first results will be presented.