| This dissertation is mainly concerned on two problems. Aimed that the hide-exposing action between the different size of non-uniform sand particles, threshold wind velocity, for non-uniform sand particles, in which bed-sand's position relation expressed by the common tangential angle, is proposed in this paper. And aimed the fact that the influence of saltating particle' spinning has not been taken into account when calculate the sand transport rate for the spinning is a stochastic and complex process, the influences of the particles' spinning on wind-blown sand saltation are simulated in this dissertation.Firstly, taking the angles between the internally common tangents of initiating particle to its windward and leeward sand particles and horizontal plane as parameters to present hide-exposing action, the expression which gives the relation between wind velocity and diameters of initiating particles of non-uniform is determined. Then, according to the coefficients determined by experimental data, the threshold wind velocity of each size fraction is calculated in. The correlative coefficient between the calculated results and the experimental data is 0.9411, which suggests that the calculation model in this paper is reasonable.Next, based on the distribution functions of initial velocity and initial angular velocity of sand particles, a theoretical model of the wind blown sand movement at the steady state, where coupled interaction between saltation particles and wind and the influence of Magnus force were taken into consideration. The results show that sand saltation movements are obviously influenced by Magnus force, and compared with the results when Magnus force is not considered, the results in this paper are much closer to the corresponding experimental values. The calculated results also suggest that the impact velocity obeys exponential distribution and the impact angular velocity obeys the unimodal asymmetric distribution. |
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