Time-period flow of a viscous liquid past a body
  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. 
Giovanni P. Galdi, Mads Kyed
math.AP