  We consider both the effect of particle inertia on stochastic Stokes' drift,
and also a related process which could be considered as a crude model of
stochastic Stokes' drift driven by an eddy diffusivity. In the latter, the
stochastic forcing is a stable OU process rather than Brownian motion. We show
that the eddy Stokes' drift velocity has a peak at a non-zero value of the
correlation time-scale for particles that have the same (limiting) diffusivity.
For both of the models considered, this study shows that not only can
stochastic Stokes' drift be used to sort particles with different
diffusivities, but also it can be used to sort particles of the same
diffusivities but with different particle masses or correlation time-scales.
This effect may be important in particle sorting applications.
