Long-time rotational motion of a set of rigid bodies immersed in a viscous fluid

The long-time rotational motion of a set of rigid bodies immersed in a viscous fluid is studied on the basis of the linearized Navier-Stokes equations. After an initial twist applied to one of the bodies the rotational motion of each of them decays at long times with a t-5/2 long-time tail. The coefficient of the tail depends on shape and configuration of the bodies. It is shown that it can be expressed in terms of zero frequency mobility tensors that in principle can be calculated from the steady-state Stokes equations.