坡面细沟侵蚀过程的水动力学特征试验研究

Study on Hydrodynamic Characters of Runoff in Rill Erosion Process on Slope

通过不同坡度、不同流量的组合放水冲刷试验 ,对坡面细沟侵蚀发生过程中的坡面流水动力学特性进行了研究。结果表明 ,在试验的坡度和流量范围内 ,坡面流的雷诺数变化于 36 2～ 4 2 84之间 ,并且其变化有随冲刷历时和流量的增大而增大的趋势。而坡面流弗劳德数在整个试验过程中均大于 1,属于急流范围。坡面流阻力系数的大小与水流雷诺数有关 ,但其变化趋势受坡度的影响。在坡度较缓时 ,阻力系数随雷诺数的增大而减小 ;在坡度较大时 ,阻力系数随雷诺数的增大而增大。在径流冲刷侵蚀过程中 ,径流流速并非一恒定值 ,而是随冲刷时间的延长和坡面冲刷形态的变化呈现出先减小后稍增大的趋势。

The hydrodynamic characters of runoff in the process of rill erosion were studied by using runoff scouring experiment under the different slope gradients and the different flow discharges. The results show that the reynolds number of the flow varies between 362 and 4 282 in the erosion process, based on the various of reynolds number the erosion process can be divided the sheet erosion stage and the rill erosion stage. The Froude number of runoff flow larger than 1 under the all experiments and it is belongs to the turbulent condition. Roughness coefficients in rills that are easily affected by the slope gradient, are closely related to reynolds number. That is, the roughness coefficient decreased with the increase of reynolds on steep slope. Flow velocity showed a little increase after a decrease with experiment time length of scouring and the variation of soil bed irregular in profile and cross section.