Abstract:

In this paper， the wind-sand environment wind tunnel simulation was used to measure the sand transport volume， wind-sand flow structure and particle size characteristics of the near-surface wind-sand flow in the gobi under different wind speeds and different gravel coverages. The variation law of gravel coverage on the bed surface under different wind speeds was analyzed to reveal the wind-sand movement on the gobi surface and its influence on the change of gravel coverage on the underlying surface. The results show that： （1） The bed gravel coverage is divided into low and high coverage with 12% as the boundary. Under low gravel coverage and high wind speed （18-24 m·s^-1）， the surface sediment transport volume of gobi changes obviously with wind speed， and the inflection point of sediment transport curve appears as " elephant trunk " effect. With the increase of wind speed， the inflection point moves up， and the smaller the gravel coverage， the greater the curvature of sediment transport profile. Compared with high wind speed， the change of surface sediment transport volume of gobi under low wind speed （6-18 m·s^-1） is not obvious， indicating that the change of sediment transport volume under low gravel coverage is mainly controlled by wind speed， and high gravel coverage has an inhibitory effect on wind sand flow. （2） With the increase of gravel coverage on the bed surface， the frequency distribution curve of sediment transport particle size has a downward trend. The gravel coverage has little effect on the frequency distribution of sediment transport particles， which shows a single peak distribution and only affects the mass percentage of the peak value of the curve. It shows that when the wind speed is constant， the particle size distribution of sediment transport particles in wind-blown sand flow is less affected by gravel coverage. （3） In the process of wind-sand movement， the gravel coverage of gobi bed increases linearly with the increase of wind speed， and there is a strong linear correlation between them. The variation of different coverage under high wind speed is greater than that under low wind speed.

Key words: wind tunnel simulation, gobi, wind-sand movement, underlying surface, gravel coverage