Granular materials, such as powder, agricultural grains and sand, play important roles in our life. Further, their collision processes are taken as one of fundamental processes observed in natural fields. In particular, the way how sand grains are ejected from ground surface when wind-blown grains hit them is an important issue for understanding stationary sediment transport. The whole process, starting from the initial impact of a grain and ending with ejection of many grains, are shortly called “splash process”, and the transport of grains near the surface is sustained by splash process.
For this reason, splash process has been extensively studied with experiments, and previous experiments have shown the relations between the incident angle/speed of the impacted grain and ejection grains’ angle/speed . We have simulated the splash process with similar system to previous experiments using the discrete element method (DEM) and obtained the qualitative agreement with these experimental results. Moreover, we found that ejection grain dynamics varies depending on their ejection timing after the initial impact, which is reflected to the drastic change of the ejection velocity distributions . This result suggests that the way of impact propagation along and beneath the granular bed surface varies according to the timing after the impact. For the next step, we have investigated the relation between the grain ejection process and the force propagation process beneath the granular bed surface induced by the impact of a grain onto the granular bed surface. To elucidate this relation, we have focused on the “force path” which gives the connection from the initially impacted grain through force propagation to ejected grains by numerically analyzing binary contacts inside the bed with simple definition. We will show the relation between force propagation process and ejection process taking care of inner dynamics of granular bed.
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