Scaling laws for liftoff velocity for wind-transported particles during particle-bed collisions

We performed wind tunnel studies of sand–bed collisions with natural sand particles and found an impact angle of 10.5o over a loose bed, and calculated the critical impact velocity (vic ≅ 1.2027 m s-1). The number of splashing particles (Ns) increased linearly with vi, but the coefficient of restitution CoR decreased linearly with vi. The momentum lost through frictional processes αlost was insensitive to vi, with a value of 0.2466. The mean splash velocity increased with vi for vi < 7 m s-1, and gradually reached its maximum value (0.7534 m s-1) at vi = 7 m s-1, whereas decreased slowly with vi for vi> 7 m s-1 and gradually approached a constant (0.6137 m s-1). In addition, we developed a probability distribution model for liftoff velocity. Our results emphasize the crucial role of the impact angle and have significant consequences for modeling sand–bed collisions in a natural environment.