Hydrodynamic radius approximation for spherical particles suspended in a viscous fluid: influence of particle internal structure and boundary.

Systems of spherical particles moving in Stokes flow are studied for different particle internal structures 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.