The effect of wind speed and bed slope on sand transport

Abstract

This paper reports on a wind tunnel study of the effects of bed slope and wind speed on aeolian mass transport. The use of a sloping wind tunnel has enabled estimation of the friction angle α to be about 40° for saltating particles in the range 170–540 μm. A formula relating dimensionless mass transport to friction speed and bed slope is proposed, and mass transport data for five uniform sand samples and one non‐uniform sand sample are shown to fit the equation well. In particular, the relationship reveals an overshoot in mass transport slightly above threshold collisions, a feature also evident when previous experimental data is re‐examined. As the number of mid‐air collisions between the saltating particles increases greatly with wind speed, the overshoot may occur as a result of increasing energy losses resulting from the collisions. Finally, it is demonstrated that data for saltating snow shows a similar overshoot in the dimensionless transport rate.