Wind speed characteristics and blown sand flux over a gravel surface in a compact wind tunnel

We investigated the influence of gravel coverage on roughness length and blown sand flux in a compact wind tunnel equipped with a turbulence generator and a piezoelectric blown sand meter. At gravel coverages from 5% to 15%, roughness length increased with increasing coverage. However, at coverages of 20% or greater, roughness length reverted to its value at 0% coverage. At the lowest wind speed of 6 m s(-1), blown sand was fully trapped at gravel coverages of 15% or greater; however, coverage affected sand flux little at wind speeds of 8 and 9 m s(-1) and had no effect at a wind speed of 10 m s(-1). The increase in roughness length with gravel coverages from 5% to 15% corresponded to a decreased blown sand flux at heights less than 8 cm. However, at 8-cm height, a greatly decreased roughness length at higher gravel coverages (20%-30%) corresponded to a notable increase in blown sand flux, a change we attribute to aerodynamic smoothing.