黄土坡面细沟与细沟间水流水动力学特性研究

Study of hydrodynamic characteristics of rill and inter-rill flows on loess slopes

采用室内人工模拟降雨试验，使用5m长的移动式可调坡钢制土槽，通过2个降雨强度（1．5和2mm／min）和4个坡度（10°、15°、20°、25°），对黄土坡面细沟侵蚀发生过程中的坡面径流水动力学参数特征进行了研究。结果表明：（1）细沟内水流的平均流速一般大于同水平面上细沟间水流平均流速，二者变化规律不同，细沟内水流流速的变化与细沟形态变化有关，当测速坡段内有跌坎时，测得流速就会减小；（2）雷诺数和弗汝德数的变化都与对应的水流平均速度变化规律相同，与坡度的不同所表现出的变化规律并不明显；细沟内水流Re和n的值比细沟间水流一般要大；（3）Darey·weisbaeh阻力系数（，）和曼宁阻力系数（n）受坡度的影响比较显著，二者呈较好的线性关系；径流阻力系数（，）与雷诺数（Re）之间并无显著关系，而与弗汝德数（n）之间的关系显著；细沟内水流阻力系数一般小于细沟间水流阻力系数，特别是在坡度较大的情况差异更为显著；（4）水流功率和水流剪切力都随坡度的增大而呈先增后减的趋势，临界坡度在20°-25°之间；同一坡度下细沟流与细沟间水流之间关于平均径流剪切力和水流功率的差异并无显著规律。

Through conducting rain simulation experiments under different rainfall intensities （ 1.5 mm/min, 2.0 mm/min） and on different slopes （10° , 15° , 20° , 25°） , the runoff hydrodynamic characteristics during the process of rill erosion are discussed. The results show that： （ 1 ） The average velocity of rill flow is general ly larger than the interrill flow velocity at the same water level, the velocity of rill flow changes with the mor phology of rill. Where there is a measurement sill, the flow speed will be reduced. （2） The Reynolds number and Froude number change with the change of average flow velocity, changes on the different gradients are not obvious ; the Reynolds number and Froude number of rill flow are generally larger than the corresponding num bers of interrill flow. （3） The DarcyWeisbaeh resistance coefficient and Manning roughness coefficient are influenced by the slope significantly, and there is a good linear relationship between them. The relationships between the drag coefficient of runoff and the Reynolds number are not significant, but there is a significant re lationship between the drag coefficient of runoff and the Froude number. The drag coefficient of rill flow is generally less than the drag coefficient of interrill flow, the difference is more significant especially on large gradients. （4） The stream power and flow shear stress increase with the slope firstly and then decrease, the critical slope is between 20° and 25°. On the same slope, the difference of average runoff shear stress and stream power of rill flow and of interrill flow has no significant regularity.