Concentration dependence of spin friction coefficients in suspensions of parallel cylinders and spheres

Abstract

Numerical calculations have been made of the spin friction coefficient of both an infinite array of suspended parallel cylinders and an array of cylinders sandwiched between two plates. At low cylinder volume fractions the results can be expressed in terms of a virial expansion in volume fraction and the first and second virial coefficients have been determined. The results for an infinite array are compared to a cell model in which the flow around a reference cylinder is calculated. The agreement between both methods is excellent. For spheres, the results of the rotary friction coefficient, calculated using a similar cell model, differ from literature data obtained using a cluster expansion. These results have a bearing on the concentration dependence of the rotary friction and rotary diffusion coefficients of spherical and non-spherical particles.