We carried out wind-tunnel experiments on windblown sand that highlight a transition from saltation to collisional regime above a critical wind strength. This transition is characterized by a non-linear increase of the mass transport rate with the wind shear strength. Discrete numerical simulations confirm the experimental findings and ascertain that mid-air collisions are responsible for this change of flow regime. This discovery opens new lines to unravel the unresolved issue of aeolian sand ripples.
This work has been published in Physical Review Letters : link to HAL Archives