  We consider a mass-spring system immersed in an incompressible fluid flow
governed by the Navier-Stokes equations subject to a prescribed time-periodic
flow rate (and possibly external time-periodic body forces on the fluid and the
mass). We show that, with no restriction on the period of the flow rate (and of
the external forces), when the flow rate is "small", there exits a weak
time-periodic solution to the coupled system. Under some more regularity and
"smallness" conditions on the flow rate (and the external forces) we also show
that these solutions are, indeed, strong solutions.
