The effect of wind speed and bed slope on sand transport |
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Authors: | James D Iversen & Keld R Rasmussen |
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Institution: | Department of Aerospace Engineering and Engineering Mechanics, Iowa State University, 304 Town Engineering Building, Ames, Iowa 50011, USA [E-mail:;], Department of Earth Sciences, Åarhus University, Building 520 Ny Munkegade, 8000 Århus C, Denmark [E-mail:;] |
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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. |
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Keywords: | Bed slope sand transport wind tunnel |
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