We study the behaviour of heavy inertial particles in the flow field of two like-signed vortices. In a frame co-rotating with the two vortices, we find that stable fixed points exist for these heavy inertial particles; these stable frame-fixed points exist only for particle Stokes number $St<St_{ cr}$. We estimate $St_{ cr}$ and compare this with direct numerical simulations, and find that the addition of viscosity increases the $St_{ cr}$ slightly. We also find that the fixed points become more stable with increasing $St$ until they abruptly disappear at $St=St_{ cr}$. These frame-fixed points are between fixed points and limit cycles in character.
Categories: physics.flu-dyn nlin.CD