Abstract: In order to further understand the instantaneous horizontal wind velocity profile characteristics in aeolian sand transport and clean air, the instantaneous horizontal wind velocity profiles were measured in wind tunnel with sampling time interval of 0.01 s. The characteristics of instantaneous horizontal wind velocity, instantaneous friction velocity and instantaneous aerodynamic roughness in aeolian sand transport and clear air are analyzed. The results show that in the same free-stream wind velocity, the horizontal wind velocity fluctuation intensity in windblown sand movement is stronger than that in clear air. The instantaneous friction velocity, instantaneous aerodynamic roughness and their fluctuation in aeolian sand transport are more than that in clear air. The probability density distribution of instantaneous friction velocity both in aeolian sand transport and clear air obeys the normal distribution, while their eigenvalue is different. The probability density distribution of instantaneous aerodynamic roughness in clear air shows a monotone decreasing distribution, while in aeolian sand transport, a single peak appears in the probability density distribution of instantaneous aerodynamic roughness. Therefore, in the same free-stream wind velocity, the characteristics of instantaneous horizontal wind velocity profile in aeolian sand transport and clean air show an obvious distinction.

Key words: instantaneous horizontal wind velocity, friction velocity, aerodynamic roughness, aeolian sand transport