  Time-periodic solutions to the Navier-Stokes equations that govern the flow
of a viscous liquid past a three-dimensional body moving with a time-periodic
velocity are investigated. The net motion of the body over a full time-period
is assumed to be non-zero. In this case the appropriate linearization of the
system is constituted by the time-periodic Oseen equations in a
three-dimensional exterior domain. A priori Lp estimates are established for
this linearization. Based on these estimates, existence of a solution to the
fully non-linear Navier-Stokes problem is obtained by the contraction mapping
principle.
