Abstract
The effect of permeability on the rectilinear oscillations of two rigid spheres moving through an unbounded viscous fluid about their axis of symmetry with no slip is investigated. A collocation technique was employed to execute the conditions on the surfaces of the rigid spheres. The in -phase and out-phase forces are obtained and expressed graphically for various parameters. In addition, the streamlines are plotted for different relevant parameters. The limiting cases of Stokes and Darcy's flows are discussed.