A Function for Sand Movement by Wind

摘要

A method for calculating the rate of transport was developed. This method was based on experience gained in the field of sediment motion in rivers and all available field and wind tunnel data on the subject. It has been found that the basic forces causing the sediment motion are those of the average lift L and the fluctuating part L caused by the turbulence. Another factor contributing to the motion in the case of wind is the effect of impact, caused by the particle in saltation, in disturbing the bed surface. The effect of impact was found to be a function of the main forces causing the motion and therefore it was introduced as a correction for the mean lift force caused by the distortion of the fluid field around the bed particles. It has been found that the basic principles governing the rate of sediment transport by water and air are the same. The only difference was found to be the effect of saltation on disturbing the bed surface in the case of air. The results of this study are represented as a theoretical relation between the flow intensity and the intensity of sediment load. The effect of particle hidding in the laminar sub-layer was combined with the impact correction to give a final wind correction which proved to be a function of the parameter discribing the ratio between the submerged weight of the particle and the mean lift force. The method is applicable for calculating the rate of sand transport under a wide range of wind velocities and for sand sizes ranging from a 0.145 mm to 1.00 mm. Application of the derived method for calculating sand transport by wind from natural beaches is given. (Author)