Some Numerical Investigation Into Sand Grain-Slope Bed

It is considered to be necessary to study sand grain/slope bed collision process on the issue that whether the splash function about single sized flat bed can apply to that of slope bed. In this paper. Aimed at this issue, DEM and soft-model approach are combined with to do direct numerical simulations of sand grain/slope bed collision process in wind-blown sand. Firstly, the particle size distribution of the sand bed surface is generated by stochastic method, and the stable sand bed surface is generated by the natural sedimentation method. On the basis of this study, the rebound and sputtering characteristics of the collision between the incident particles and the bed surface are studied, and they are compared with that of the flat bed surface. Then, further analysis of the effect of bed slope、incident velocity、incident angle、incident scale on the jump process of impact collision are conducted, and the relationships between the physical quantities of the incident and take off at different bed slope, particle size, incident angle are given. And the relationship between input variables and take-off physical quantities under different slopes were analyzed in detail. Finally, we summarized the influence of bed slope on the grain/bed collision process, the sand/bed collision law including the incident angle and velocity, and the san/bed collision law at the same time including the incident velocity and particle size. The main works are concluded as follows:1. On the issue of whether the splash function about single sized flat bed can apply to the process of slope bed, the grain-bed collision processes on flat bed and on slope are compared, and give the differences between the two results quantitatively and qualitatively. The research finds that the splash function can not be directly applied to the slope research, the two results are different. Therefore, it has a great significance to study the grain-bed collision in the wind blown sand flow on the complex bed surface, which is a sufficient basis for the next step to study the correlation between the incident variables and the take-off characteristics.2. Considering under different slopes, the incident velocity and the incident angle may have some impacts on the grain-bed collision. then we give the splash functions on different bed, including the distributed law of sputtering velocity and sputtering angle.3. Considering under different slopes, the influence of incident scale and incident speed to the grain-bed collision. Proposing influence degree of grain size on the characteristics of takeoff sand particles, also give the relationship between the volume of take-off and the incident physical quantity.