  Systems of spherical particles moving in Stokes flow are studied for a
different particle internal structure and boundaries, including the Navier-slip
model. It is shown that their hydrodynamic interactions are well described by
treating them as solid spheres of smaller hydrodynamic radii, which can be
determined from measured single-particle diffusion or intrinsic viscosity
coefficients. Effective dynamics of suspensions made of such particles is quite
accurately described by mobility coefficients of the solid particles with the
hydrodynamic radii, averaged with the unchanged direct interactions between the
particles.
