Wind tunnel experiment of equilibrium transport of soil-like grains

Aeolian grain transport on the soil-like surface composed of fine sand and silt is measured in a wind tunnel. It is found that the form of mass flux profile of sand is different from that of silt. Mass flux profile of sand is a straight line in log-linear plot but mass flux profile of silt is more like a third power curve, and the silt fraction in the soil-like surface has slight effect on the slope of sand mass flux profile but affects the amount of total sand transport rate. According to the effect of silt on the motion of sand grains, a critical silt mass fraction in the surface layer is revealed. For the grain material during this experiment, the critical value approaches 15%. When the silt mass fraction is below the critical value, sand transport rate increases with silt mass fraction. However, when the silt mass fraction is beyond the level, sand transport rate decreases with silt fraction. And the sand ripples on the surface arise obviously with the increasing silt mass fraction and wind speed, but disappear as silt mass fraction exceeds 15%.