Dresden 2011 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 13: Fluid Dynamics and Turbulence I

DY 13.8: Vortrag

Dienstag, 15. März 2011, 12:15–12:30, ZEU 118

Measuring the onset of the Rayleigh-Taylor instability in a rotating magnetic field — •Andreas Pöhlmann, Ingo Rehberg, and Reinhard Richter — Experimentalphyisk V, Universität Bayreuth, Germany

If a dense fluid is supported by a less dense fluid, the flat interface separating them is subject to the Rayleigh-Taylor instability. The interface tension between the fluids suppresses the growth of all unstable modes with wavenumbers greater than the critical wavenumber. This gives rise to a maximum experimental interface diameter (size of boundary) at which the flat interface is stable.

In the case of one of the fluids being magnetic, an azimuthally rotating magnetic field can be used to stabilize modes with wavenumbers smaller than the critical wavenumber [1]. This allows for the preparation of the flat interface with greater interface diameters. When switching off the field, all unstable modes, which are not suppressed by the size limitation of the experiment, start to grow. Consequently, a precise study of the Rayleigh-Taylor instability should be possible.

In our experiment a magnetic fluid is covered by a more dense transparent one. The flat interface is stabilized by a rotating magnetic field. The interface size is restricted to a circular shape. For different diameters the field strength is lowered to a threshold level, so that the stability boundaries can be observed. They are compared with the predictions of Ref.[1].

[1] D. Rannacher and A. Engel, Phys. Rev. E, 75, 016311 (2007).