基于医用CT技术的泥沙颗粒相对隐蔽度分布规律试验研究

Incipient motion of sediment which research subjects to the cognition of regularity of distribution in relative hidden degree of sediment particles is the initial critical state of sediment transport. So far, design formulas of relative hidden degree of uniform and non-uniform sediment were established, its concepts of 2-D and 3-D were studied, and the phenomenon and character of incipient motion of sediment and its mathematical description have been made some progress by scholars both at home and abroad..Structure of turbulence near the bed surface, which is susceptible to the various shapes and stochastic permutation of sediment particles and is confined by the experimental approach, is very complicated. So the concealed or exposed coefficient of sediment was used to generalize the influence of sediment, however, this research was confined to the theoretical analysis level upon the flat bed surface chronically..Centre on incipient motion mechanism of sediment, the major science and technology problems in this project include the generalized model and its statistical distribution of relative hidden degree of sediment, the thickness of moving layer and expectation of relative hidden degree of sediment, the regularity of distribution of relative hidden degree under different bed slops conditions, and the research and development of experimental approaches. The discretionary space structure of bed surface could be scanned by the medical Computed Tomography technique, so this project would adopt this technology to extract the relative position among sediment particles. The regularity of distribution of relative hidden degree of uniform and non-uniform sediment particles under critical incipient condition on bed slop and bank slop would be studied by means of CT and Image analysis techniques. Implementation of this project would promote the basic research progress on incipient motion and transport of sediment effectively to a certain degree.

泥沙起动为泥沙输移初始临界状态，其研究受制于泥沙颗粒相对隐蔽度分布规律的认识，国内外学者在散体均匀沙及非均匀沙相对隐蔽度计算式建立、二维及三维泥沙颗粒相对隐蔽度分析、泥沙起动现象及特性数学描述等方面取得一定进展。.泥沙颗粒形状各异、排列随机等因素导致水流紊动床面内部结构复杂，受实验手段困扰，只能借助隐蔽系数概化泥沙起动影响，研究长期局限在平坡床面理论分析层面。.平坡/坡度条件下泥沙颗粒相对隐蔽度模型概化及其分布规律、非均匀沙相对隐蔽度最小值及可动层厚度、及试验手段研发等均为泥沙起动研究主要科学技术问题；计算机断层扫描（医用CT）技术能实现全息扫描床面泥沙任意空间结构，本项目拟采用该技术提取泥沙颗粒间相对位置关系，运用图象分析及片光源技术，研究底坡/岸坡床面上近壁水流结构及均匀/非均匀沙颗粒在临界起动状态下相对隐蔽度分布规律；项目实施一定程度上将有效推动泥沙颗粒起动及输沙率等基础研究进展。

推移质运动是河流动力学研究的基础，以科学的方法对其进行研究已逾百年，由于该领域涉及内容较为宽广且极为复杂，取得公认的研究成果不多。.围绕推移质运动基本规律，本文从四个方面对其进行研究：.⑴ 归纳提出了表层沙摩擦角的物理概念，通过试验论证了泥沙休止角与表层沙摩擦角之间的区别，论述了非均匀沙休止角随分选系数的变化规律，初步探讨了偏度系数与峰度系数对非均匀沙休止角的影响，针对非均匀沙休止角及表层沙摩擦角的工程应用，提出了非均匀沙的最优化级配设计方面的建议。.⑵ 针对泥沙起动条件，同时考虑了水流紊动特性和泥沙颗粒排列的随机性对泥沙起动的影响，利用泥沙滚动起动模型计算得出泥沙起动条件并不是一个确定值，而是随机分布在一个区间内；针对泥沙起动概率，从面积比、数量比和时间比三个角度重新阐述了Einstein (1950)泥沙起动概率的物理图景，推求了一个新的泥沙起动概率计算模型，并从水流上举力分布、起动概率积分区域及泥沙颗粒受力三个方面论证了Einstein (1950)起动概率模型的合理性。.（3） 医用CT机的泥沙运动研究方面：设计研制出配套CT机专用变坡水槽一座；了解掌握CT设备的各项技术参数、细节及各种使用技巧和注意事项，剖析了CT机断层扫描原理，进行了基于C/C++ 版数据分析程序研发；对泥沙体形态特征进行了初步的CT扫描及参数分析，获得初步成果。.（4） 2015年，由于实验室周边大型土建工程施工开挖影响，使得CT机房地面严重塌陷，导致CT机倾斜无法正常使用，一直到2016年底设备商西门子公司才安排技术人员对CT机进行了移机并调校，使得CT机恢复正常工作，严重影响了本基金项目的开展，部分试验工作有待延后进行，在此说明。.（5） 项目成果发表SCI论文2篇、EI论文1篇、核心刊物论文1篇，申请、获批发明专利4项。