Regensburg 2007 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 26: Ferrofluids / Liquid crystals
DY 26.4: Vortrag
Donnerstag, 29. März 2007, 11:15–11:30, H3
Maximal growth rate at the Rosensweig instability — •Adrian Lange1, Holger Knieling2, Gunar Matthies3, Ingo Rehberg2, and Reinhard Richter2 — 1Fraunhofer Institut für Werkstoff- und Strahltechnologie, Winterbergstraße 28, D-1277 Dresden — 2Experimentalphysik V, Universität Bayreuth, D-95440 Bayreuth — 3Ruhr-Universität Bochum, Universitätsstraße 150, D-44780 Bochum
Instabilities in magnetic fluids (MFs) have had a long history with the most eye-catching phenomenon being the Rosensweig instability [1]. When a critical value Bc of the vertical magnetic induction is surpassed, static liquid peaks arranged in a hexagonal pattern are rising on the free surface of the fluid. A linear description of the Rosensweig instability is amenable in theory, but restricted to small amplitudes. In experiments they can be observed only for a very short time during the increase of the pattern of ridges, which bifurcate supercritically. Thus a new pulse technique has been developed and applied [2,3]. It is assumed that in the linear state of the pattern forming process the wave number with the largest growth rate will prevail. This contribution is devoted to present theoretical, experimental, and numerical results for the maximal growth rate for two different MFs. The results show that the experimental and numerical data agree satisfyingly whereas the theoretical data show a sizeable disagreement. [1] M. D. Cowley, R. E. Rosensweig, J. Fluid Mech. 30, 671 (1967).[2] A. Lange, B. Reimann, R. Richter, Phys. Rev. E 61, 5528 (2000).[3] B. Reimann, R. Richter, I. Rehberg, A. Lange, Phys. Rev. E 68,[3] 036220 (2003).