Regensburg 2007 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 30: Poster II

DY 30.58: Poster

Donnerstag, 29. März 2007, 16:00–18:00, Poster D

Rheological properties and the disturbance of the pair correlation function in clusters of oriented dipolar particles — •Stefan Fruhner and Siegfried Hess — Institut für Theoretische Physik, Technische Universität Berlin, D-10623, Germany

Clusters of colloidal dipolar particles are studied with the help of Non Equilibrium Molecular Dynamics (NEMD). This allows to study the local structure and rheological properties in magneto-rheological fluids [1] and in (inverted) ferro-fluids. A surrounding wall potential keeps the particles together. It can be regarded either as effective interactions with the surrounding fluid or as “walls” of a particle trap. The paricles are exposed to a homogeneous shear flow and they are subjected to a Gaussian thermostat. The dipole-dipole interaction and the shear flow render a distortion of the pair correlation function. A more complex anisotropic description for the directional dependence is needed [2]. The pair correlation function can also be approximated by the Maxwell-Stokes relation [3] for small shear rates. With the knowledge of the pair correalation function other quantities can be computed, i.e. the pressure and viscosity. The pressure tensor can also be obtained directly from the simulation, so a comparision of both methods is possible.

[1] M.Kröger, P.Ilg and S. Hess, J. Phys.: Condens. Matter 15(2003) S1403-S1423
[2] H.J.M. Hanley and S.Hess: “Pressure Tensor and Viscosity Coefficients of a Soft Sphere Liquid Under Shear”, J. of Thermophysics Vol.4 No.2 (1983)
[3] H.J.M. Hanley, J. C. Rainwater and S. Hess: “Shear-induced angular dependence of the liquid pair correlation function”, Phys. Rev. A 6, 1795 - 1802 (1987)