Spreading dynamics of a particle suspension plug in oscillatory carrier flow*

We present a numerical analysis of the spreading dynamics of a particle suspension plug subject to oscillatory motion of the carrier fluid in the absence of gravity. The study focuses on the finite Reynolds number flow regime (order 1-10) and compares the resulting dynamics with the results of the experimental system behavior in the low Reynolds number flow regime, provided by our experimental collaborators. Numerical simulations use particle-resolved Direct Numerical Simulations (pr-DNS) to identify the main control parameters affecting the particle spreading dynamics. Spreading dynamics is characterized by the bulk and individual particle drift along the fluid flow, dynamic shape of the particle suspension plug, as well as by particle movement statistics in between the fluid layers. Control parameters considered in the study include applied strain amplitude (i.e., the distance travelled by the particles during one oscillation), Reynolds number of the flow, particle concentration, and particle inertia. Additionally, we compare the particle spreading dynamics with the dynamics of just the fluid elements in oscillatory flow.