MOTION OF A SPHERE IN A VISCOUS INCOMPRESSIBLE FLUID AT LOW REYNOLDS-NUMBER

We study the motion of a sphere in a viscous incompressible fluid at low Reynolds number on the basis of the equation of motion derived by Basset and Boussinesq. We show that the motion after a sudden impulse deviates strongly from the exponential solution of the Stokes equation of motion, if the mass of the sphere is not much larger than the mass of the displaced fluid. We relate this to the form of the relaxation spectrum.