Transverse swimming in a dilute suspension of active swimmer under an oscillating shear flow

Simulations of a dilute suspension of pusher swimmers under an oscillating shear flow show that a large fraction of them swim preferentially in the vortex and flow direction, perpendicular to the gradient direction. These two directions alternate in a collective way among all the swimmers. Experiments of a suspension of E.Coli in a Hele-Shaw cell under an oscillating flow manifest the same behavior.