In Stokes flow, Purcell's scallop theorem forbids objects with time-reversible (reciprocal) swimming strokes from moving. the presence of inertia, this restriction is eased and reciprocally deforming bodies can swim. A number recent works have investigated dimer models that swim at intermediate Reynolds numbers ${\textit Re} \approx 1$ –1000. These show interesting results (e.g. switches direct...

Choi & Joseph (2001) reported a two-dimensional numerical investigation of the lift-off of 300 circular particles in plane Poiseuille flows of Newtonian fluids. We perform similar simulations. Particles heavier than the fluid are initially placed in a closely packed ordered configuration at the bottom of a periodic channel. The fluid-particle mixture is driven by an external pressure gradient. ...