“径向粗化”机理解析  

Mechanism of downstream coarsening in the transport of non-uniform bedload sediments

作　　者：王玉海[1] 陆培东[1] 喻国华[1] 刘家驹[1] 

机构地区：[1]南京水利科学研究院水文水资源与水利工程国家重点实验室,江苏南京210024

出　　处：《泥沙研究》2006年第4期68-72,共5页Journal of Sediment Research

摘　　要：不断增加的野外证据和室内水槽试验的结果表明:在一定的空间尺度内,非均匀底沙在向下游输运的过程中会出现“径向粗化”的现象,即颗粒级配沿径流方向增大的现象。本文基于热力学第二定律和泥沙运动力学的相关理论,探讨了形成这一特殊现象的内在机理。研究表明,“熵致相变”和“体积排斥效应”决定了具有混合粒径的颗粒系统在趋向平衡态的演化过程中,不同属性的颗粒会发生分异而相同属性的颗粒则会聚集在一起,特别是粗颗粒群体通常集中分布在系统的边缘处。但是这一过程的实现不仅需要外部对称破坏场如水流的剪切作用等来触发和强化,也需要通过“逆序级配”的运动途径来实现。而后者则是由以碰撞作用为主的颗粒运动中产生的法向离散力所决定的。Downstream coarsening means that coarse grains move faster than fine grains and tend to concentrate at the front of the non-uniform bedload flow. Based on the Second thermodynamic law and theory of sediment transport, this paper explores the intrinsic mechanism for this phenomenon. Entropic ordering and ＂volume exclusion effect＂ could lead to the segregation of dissimilar grains and aggregation of similar grains and that the coarse grains are most likely to concentrate beside an edge of the system. But the realization of this process needs not only the initiation and enhancement by external symmetry-breaking fields/forces, such as shearing water flow and gravity, but also the inverse grading （i.e. the coarse grains are running over the fine grains）

关 键 词：非均匀底沙 熵致相变 对称破坏 逆序级配 径向粗化 

分 类 号：TV14[水利工程—水力学及河流动力学]