Investigation of the statistical features of sand creep motion with wind tunnel experiment

•Sand creep motion is an important mechanism in aeolian sand transport.•A wind tunnel experiment was conducted to record sand creep motion.•Creep trajectories were abstracted by a discrete particle tracking algorithm.•The collection of creep trajectories was analyzed statistically.•The features of two types of sand creep motion were thereby obtained.

A wind tunnel experiment has been adopted to investigate aeolian sand creep motion which has not been sufficiently documented thus far. An image sequence that describes continuous creep motion on a flat sand bed is recorded by high-speed photography, from which numerous creep trajectories are reconstructed by a particle tracking velocimetry (PTV) algorithm. A double-peak pattern present in the distribution of the starting velocity, which indicates the first stepping velocity of creep trajectory, is used to categorize all creep trajectories into flow- or collision-initiated groups. Increased friction velocity is shown to improve the proportion of collision-initiated creep motion. The proportion of the collision-initiated starting velocity against all stepping velocities increases with friction velocity; however, that of the flow-initiated starting velocity remains steady. These results indicate that a stronger wind intensifies the intermittency (the inverse of lifespan) of creep motion by converting it into saltation.