Evolution of Streamwise Sand Transport with Distance
风沙流的输沙率沿程变化规律

A simple theoretical expression for evolution of streamwise sand transport with distance was put forward.Wind erosion is consisted of two parts,fluid erosion and impact erosion.Fluid erosion is induced by the force of airflow directly exerted on the bed while impact erosion results from the impaction of saltating grains on the bed.The former depends on the difference between local and saturation sand transport rates,while the later is merely associated with the local sand transport rate.An analytic expression for sand transport rate with distance was deduced by introducing two parts of wind erosion into the continual equation of erosion.Prediction from the expression was compared with the measurement in the wind tunnel,and satisfactory agreement was achieved.Based on the expression,two erosion rates with distance,fluid and impacting erosion rates,were deduced.Fluid erosion rate decreases with distance while impacting one firstly increases and then decreases with distance.Also,an expression of saturation length of sand transport was introduced.