Dresden 2003 – scientific programme

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DY: Dynamik und Statistische Physik

DY 23: Ferrofluids / Liquid crystals

DY 23.1: Talk

Tuesday, March 25, 2003, 11:45–12:00, G\"OR/229

The Faraday instability on a ferrofluid with chains — •Vladislav Mekhonoshin and Adrian Lange — Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany

The parametric generation of standing waves on the free surface of a ferrofluid is studied. The interaction of a suspension of single-domain particles with an applied magnetic field gives raise to numerous interesting phenomena. In the present work we extend the previous study of the influence of a horizontal magnetic field on the generation of the Faraday waves [1] to the case of a ferrofluid with chains. The chains can be formed by dipolar forces in ferrofluids containing rather large particles.

In order to describe the motion of a ferrofluid with chains the stress tensor is used which was suggested by Zubarev and Iskakova [2]. The chains are considered to be straight and rigid. The linear stability analysis is performed by means of the standard Floquet ansatz.

It is shown that the appearance of even short chains consisting of a few particles influences significantly the threshold of the instability. The chains lead to a dramatic increase of the magnetisation relaxation time, an increase of the effective viscosity of the suspension, and to a growth of the ferrofluid susceptibility. The influence of all these factors is studied in detail: the first of them is relevant at high frequencies, whereas the others are of importance at any frequency.

This work was supported by the Deutsche Forschungsgemeinschaft under grant LA 1182/2-3.

[1] V. V. Mekhonoshin, A. Lange, Phys. Rev. E 65, 061509 (2002)

[2] A. Yu. Zubarev, L. Yu. Iskakova, Phys. Rev. E 61, 5415 (2000)