Slow viscous flow past a spinning sphere with permeable surface (Q1891919)

The paper treats the problem of viscous flow past a permeable sphere which rotates with a uniform angular velocity about its polar axis. The entire flow domain is considered as a homogeneous Newtonian medium, with the interior being a permeable surface. The tangential and azimuthal velocities of both internal and external flows are prescribed by the no- slip boundary conditions based on the Darcy law. The method of matched asymptotic expansions is used for determination of the drag coefficient at low Reynolds numbers. On the other hand, the formula for drag coefficient can also be used as a formula for the determination of permeability of the sphere.