Sedimentation of particles in concentrated magnetic fluids: numerical simulation

A. F. Pshenichnikov - A. A. Kuznetsov

Institute of Continuous Media Mechanics, Ural Branch of RAS, 1 Acad.~Korolyov Str., 614013 Perm, Russia

Abstract
Gravitational sedimentation of magnetic particles (dipolar hard spheres) is modelled by the means of Monte Carlo method and molecular dynamics. The main result of this simulation is the gradient diffusion coefficient of particles obtained as a function of the particle volume farction ϕ (ϕ ≤ 0.4) at low-to-intermediate coupling constants (1 ≤ λ ≤ 4). Based on numerical data it is shown that the applicability range of some previously used analytical models for the diffusion coefficient is mostly limited by λ ≅ 2. A new approximation formula for the diffusion coefficient is proposed. It quite accurately describes the obtained values up to λ = 4 and shows an excellent agreement with the known simulation data for the Helmholtz free energy of dipolar spheres. Figs 5, Refs 30.