Forces on particles in oscillatory boundary layers

The lift and drag forces on an isolated particle resulting from an oscillating wall- bounded flow, are approximated using direct numerical simulation and extrapolation techniques. We also confirm the existence of anomalies in the lift force, which arise from the interaction of the vortical field with the particle. Anomalies can also occur for computational reasons and these are discussed as well. This study was motivated by a long-standing question about the importance of lift forces in the dynamics of sediments in oceanic settings. To answer this question we use the numerically generated data as well as extrapolations to compute the ratio of the lift to buoyancy forces on a particle. This analysis suggests that for particles and oceanic conditions typical of the nearshore, the lift force can play a role in the dynamics of sedimentary beds.