  We investigate the sedimentation properties of quasi-neutrally buoyant
inertial particles carried by incompressible zero-mean fluid flows. We obtain
generic formulae for the terminal velocity in generic space-and-time periodic
(or steady) flows, along with further information for flows endowed with some
degree of spatial symmetry such as odd parity in the vertical direction. These
expressions consist in space-time integrals of auxiliary quantities which
satisfy partial differential equations of the advection--diffusion--reaction
type, that can be solved at least numerically since our scheme implies a huge
reduction of the problem dimensionality from the full phase space to the
classical physical space.
