Dispersion of a suspension plug in an oscillatory flow at finite Reynolds numbers*

We analyze the evolution of a suspension plug consisting of neutrally buoyant particles subjected to an oscillatory pressure gradient. It is known that at vanishing Reynolds number the dynamics of such plugs depend strongly on both the applied strain amplitude, i.e., the distance travelled by the particles during one oscillation, and on the accumulated strain. However, the behavior of a particle suspension plug subjected to oscillatory pressure gradients at finite Reynolds numbers (order 1-10) is much less well understood. We explore such flows using particle-resolved Direct Numerical Simulations (pr-DNS)., and we investigate the effects of fluid and particle inertia, particle concentration, and applied pressure gradient on the resulting particle transport dynamics. We furthermore compare the simulation results with corresponding experiments, with the goal of informing biomedical, environmental, and industrial applications of such flows.