Abstract: Wind-sand flow is a typical gas-solid two-phase flow occurring in the atmospheric boundary layer in which the sediment transport rate has a response time to the change of wind velocity named wind-sand flow response time. In this paper, we obtained that the response time of wind-sand flow is proportional to the measured height of wind velocity by field measurement. Based on the signal decomposition of instantaneous wind velocity and the correlation between near-surface sediment transport rate and wind velocity signal at different time scales, it is found that the response time increases with the decrease of wind velocity frequency. In order to obtain a quantitative rule, the response time of wind-sand flow with various parameters (period, turbulence intensity, incoming friction wind velocity and measured height, etc) in periodic flow field is analyzed by means of numerical simulation. The simulation results show that the response time is proportional to the period of wind velocity and the incoming friction wind velocity, and inversely proportional to the turbulence intensity and the height of the boundary layer. As height increases, response time first increases and then decreases.

Key words: wind-sand flow, unsteady wind field, response time, numerical simulation