坡面薄层流的数值模拟及在坡面流侵蚀研究中的应用

Numerical simulation of hillslope sheet flow and relationship between rill erosion and hill slope gradient

本文依据坡面薄层水流的动力波方程 ,由水沙动力学原理出发建立坡面细沟流侵蚀过程的模拟方法 .采用动力波模式 (一维非恒定流方程组 )计算了坡度变化时不同细沟宽度下的细沟沟内流速 ,根据数值计算得到了细沟流动的Re数 ,以及相同净雨强和坡长下能够使细沟流速达到最大的坡度 .依据泥沙运动力学的原理分析了这些结果在坡面流侵蚀过程中的意义 .模拟结果表明 ,细沟扩宽过程对坡度和坡面表土临界起动流速的变化十分敏感 .当细沟扩宽侵蚀在小区片蚀中占主要成分时 ,小区的片蚀总量常表现出与坡度和表层土使用方式的明显关系 .

A numerical simulation of sheet flow on hill slopes based on St. Venant equation is presented, in an effort to accurately calculate the hydrodynamic characteristics of rill flow during storm events. Rill flow velocities for various rill width and gradient are obtained using dynamic-wave model and corresponding Reynolds numbers are calculated. The critical slope for given rainfall intensity and slope length, at which rill flow will achieve the maximum value, is found out. It is independent of the rill width. Simulation result also indicates that the rill width is affected both by slope gradient and critical detachment velocity of surface soil on the hill slope. It is shown that the total amount of erosion is closely related to hill slope gradient and type of land use.