不规则沙粒碰撞固壁后反弹参数的实验和理论研究

The rebound parameters (rebound speed and angle) of a sand grain, after colliding with a wall, are elementary parameters for determining its subsequent trajectory, and they therefore have wide applications in both natural disaster and industry. Although the sand in practical application is ever irregular, it usually, for simplification, was treated as an equivalent sphere without considering its irregularity, which could reduce the reliability and efficiency of research results in application. So far, the research on irregular- particle-wall collision advances slowly, and our understanding is still greatly limited. This program plans to investigate the influence of particle irregularity on rebound parameters of sand after collision. The main contents are shown as follows: 1) experimentally measuring the rebound parameters of irregular sand grains with different diameters and incident conditions, after colliding on both ductile and brittle wall materials, by high-speed camera; 2) analyzing the experimental data and evaluating the sensitivity of rebound parameters to the proposed indices of irregularity with different wall materials; 3) investigating the main mechanical mechanism in collisions with different wall materials when the irregularity is considered; 4) establishing statistical expressions of rebound parameters, which include particle irregularity and mechanical properties of materials, based on results obtained above. The findings of this research will be helpful in resolving the problems that arise from practical applications, such as the reduction of abrasion and erosion in oil-gas pipe, slurry transportation (including coal and sand) in pipe, dust release estimation in field, and so on.

作为计算沙粒与固定壁面碰撞后运动轨迹的必需参数，粒-壁碰撞后沙粒的反弹参数（反弹速度和角度）在自然灾害和工业生产中有着广泛的应用基础。虽然在实际应用中沙粒都是不规则的，但研究者们往往忽略了它们的不规则性的影响，从而导致研究结果在指导实际应用时的可靠性和有效性降低。至今国内外对于不规则沙粒粒-壁碰撞过程的相关研究进展缓慢、了解有限。本项目拟针对沙粒不规则程度对粒-壁碰撞后反弹参数的影响展开如下研究：1）通过高速摄影仪实验测量不同粒径和冲击条件下的不规则沙粒冲击塑性和脆性固壁材料后的反弹参数；2）分析实验数据并评价两种固壁材料时的反弹参数对沙粒不规则程度表征参量的敏感性；3）探究考虑颗粒不规则性时沙粒与不同材料碰撞中涉及的主要力学机理；4）建立包含颗粒不规则程度表征参量和材料力学性能参数的反弹参数的统计表征形式。研究结果将为油气管道防磨蚀、管道浆体(煤和沙)输运以及沙尘释放等实际问题提供帮助。

作为计算沙粒与固定壁面碰撞后运动轨迹的必需参数，粒-壁碰撞后沙粒的反弹参数（反弹速度和角度）在自然灾害和工业生产中有着广泛的应用基础。沙粒的不规则使得它的反弹参数显示出随机性和离散性，从而使得它造成的结果（比如地表风蚀、管道内冲蚀）具高度不确定性。本项目拟通过展开实验和理论研究来评估沙粒不规则程度对粒-壁碰撞后反弹参数的影响。按照研究计划，本项目实现了不规则沙粒对不同性质固定壁面的冲击和反弹行为的实验测量，获得了大约10Tb的原始影像数据；但是，由于未能找到有效方法同时提取多颗颗粒的形状信息，从而不能获得有效的数据样本，使得本项目的理论研究部分暂无法实现。尽管如此，我们仍然数值探究了反弹参数对沙粒在结皮或固结壁面上跃移的影响。此外，在基金支持下，我们还探究了已有植被风场参数化模式在地表沙尘释放量估计上的差异、植被形状对两侧风速加速的影响以及植被背风处风速减小对种子风扩散的影响。