降雨和坡度对坡面流水动力学参数的影响

Experimental Study on Influence of Rainfall and Slope Gradient on Overland Shallow Flow Hydraulics

坡面流是土壤侵蚀和泥沙输移的动力,其水力学参数是构建侵蚀物理模型的基础.本文通过上方来水和模拟降雨试验,探讨了降雨和坡度(2.6%—25.9%)对坡面流水力学特性的影响.结果表明,坡面流速随坡度的增大而增大,而水深与坡度呈反势.总体上坡面水流呈条带状或斑点状分布,降雨具有增大陡坡表层流速效应,且平均流速与表层流速之比主要在0.4—0.7之间.一般地,坡面流有滚波产生,滚波数随坡度的增大而增加,而波高和波长在坡度为5.2%时达峰值,尔后呈减小趋势.降雨可触发更多滚波产生,但对波形影响不显著.随着坡度的增大,水流弗劳德数和阻力系数分别呈增大和减小趋势,且降雨对它们均无显著影响.在试验条件下,弗劳德数与水流阻力关系较雷诺数更为密切,这可能说明弗劳德数对坡面流阻力具有重要意义.

oil erosion and sediment transport on slopeland is mainly driven by overland flow, and flow hydraulics are great significance to the physical model of soil erosion.Under simulated rainfall and runoff from upland,the experiments on overland flow hydraulics at slopes of 2.6%—25.9% were carried out.The results showed that,overland flow velocity increased and depth decreased with increasing slope steepness.Overland flow was mainly distributed as strips or spots,and rainfall had a positive effect on surface velocity on steep slopes.The ratio of calculated mean velocity to surface velocity ranged from 0.4 to 0.7.The number of roll wave increased with slope,and its height and length increased up to a slope of 5.2% and deceased thereafter.Rainfall triggered more roll waves,but it had little effect on wave height and length.As slope increased,the Froude number increased and resistance coefficient decreased,and rainfall had no significant influence on them.Froude number had a closer relationship with resistance coefficient than Reynolds number,Therefore Froude number should be attached more importance to resistance of overland flow.