The influence of wind velocity and sand grain diameter on the falling velocities of sand particles

In this paper, sand velocities near the sand bed in aeolian sand transport were measured in a wind tunnel through an improved experimental scheme of the Particle Image Velocimetry (PIV) system and a data processing method. The influences of wind velocity and sand grain diameter on the probability distribution of the falling velocities of sand particles were investigated. Results demonstrate that wind velocity and sand grain diameter have no obvious influence on the distribution pattern of the falling velocities of sand particles, i.e., the probability distributions of the horizontal and vertical falling velocities of sand particles follow a Gaussian distribution and a negative exponential distribution respectively, but wind velocity has an influence on the center, width and amplitude of the probability distribution of the horizontal falling velocities of sand particles, as well as the decay constant and amplitude of the probability distribution of the vertical falling velocities of sand particles. Eventually, we presented formulas to describe the probability distribution of the falling velocities of sand particles with regard to the influence of wind velocity.