Non-linear Stokes drag of spherical particles in a nematic solvent
Universität Konstanz, Fachbereich Physik - D-78457
2 Institut für Theoretische und Angewandte Physik, Universität Stuttgart Pfaffenwaldring 57, D-70550 Stuttgart, Germany
Corresponding author: Holger.Stark@uni-konstanz.de
Accepted: 8 October 2001
We present a numerical calculation for the Stokes drag of a particle in a nematic solvent. Due to the radial anchoring of the molecules at the particle surface and a uniform director field at infinity, the particle is accompanied by a hyperbolic point defect which gives rise to the so-called dipole configuration. We write the Ericksen-Leslie equation in a reduced form emphasizing the importance of the Ericksen number Er. Due to the coupling between director and velocity field, we find a highly non-linear Stokes drag. We discuss it in terms of an effective viscosity and as a function of Er. Director field and stream line patterns add to the understanding of our results. Finally, we suggest that the non-linear Stokes drag should be observable in a falling-ball experiment.
PACS: 61.30.Dk – Continuum models and theories of liquid crystal structure / 47.50.+d – Non-Newtonian fluid flows / 83.10.-y – Rheology: Fundamentals and theoretical
© EDP Sciences, 2002