Field measurements of influence of sand transport rate on structure of wind-sand flow over coastal transverse ridge

The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Province,which is one of the most typical coastal aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges.The measurement results show that,on the conditions of approximate wind velocities and same surface materials and environments,some changes happen to the structure of wind-sand flow with the increase of total sand transport rate on the crest of coastal transverse ridge.First,the sand transport rates of layers at different heights in the wind-sand flow increase,with the maximum increase at the height layer of 4-8cm.Second,the ratios of sand transport rates of layers at different heights to total sand transport rate decrease at the low height layer (0-4cm),but increase at the high height layer (4-60cm).Third,the distribution of the sand transport rate in the wind-sand flow can be expressed by an exponential function at the height layer of 0-40cm,but it changes fi'om power function model to exponential function model in the whole height layer (0-60cm) and changes into polynomial function model at the height layer of 40-60cm with the increase of total sand transport rate.Those changes have a close relationship with the limit of sand grain size of wind flow transporting and composition of sand grain size in the wind-sand flow.