AXISYMMETRICAL MOTION OF 2 SPHERICAL-PARTICLES WITH SLIP SURFACES

The slow motion of two rigid spherical particles along the line throug h their centers in an unbounded viscous fluid is considered, The fluid is allowed to slip at the surfaces of the particles, Also, the partic les may differ in radius, in slip coefficient, and in migration veloci ty (or in applied force), Using spherical bipolar coordinates, the cre eping flow equations are solved in the quasisteady situation, and the interaction effects between the particles are evaluated for various ca ses, The interaction between particles is found to be more significant when the slip coefficients at the particle surfaces become smaller. I n general, the influence of the interaction on the smaller particle is stronger than on the larger one, The creeping motion of a spherical p article in the direction perpendicular to a plane wall is also studied for the case in which the solid-fluid interfaces may have different s lip coefficients. The retarding effect of the plane wall on the motion of the particle can be very significant when the surface-to-surface d istance gets close to zero. Our results for the particle-particle and particle wall interaction parameters at any separation distance agree very well with the existing solutions for the limiting situations of n o slip and perfect slip at the solid-fluid interfaces. (C) 1995 Academ ic Press, Inc.