An experimental study of Froude number effect on wind-tunnel saltation

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Summary

The simulation of the natural process of saltation in a wind tunnel is considered. The pioneering interactive boundary-layer analysis of Owen and Gillette [11] concluded that an independence Froude number criterion did apply to the problem and they estimate, based on wind-tunnel Froude number data ranging from 35 to 80, an independence Froude number value of about 20 for saltating flows to be free of facility constraints imposed on the saltation. The present experimental flows had Froude numbers ranging from about 6 to 1000. Analysis of friction speed variation as a function of downstream position suggests a more conservative critical Froude number value of 10 be used. Also, there appears to be an additional requirement, for most of our data, that tunnel’s downstream length-to-heigt ratio be greater than 5. Therefore, a maximum Froude number of 10 and minimum tunnel length-to-height ratio of 5 is suggested to insure accurate saltation tunnel simulation.