长江上游坡耕地细沟径流水动力学特征研究

Study on Hydrodynamic Characteristics of Rill Runoff in the Slope Land at the Upstream of Yangtze River

以长江上游为研究区域,选取了5个试验点,5种主要耕作土壤类型,进行大田人工模拟径流实验,并对坡耕地细沟径流水动力学特征进行了分析。结果表明:细沟径流流速随流量的增大而增大,且流速与流量呈幂函数关系,其指数值在0.23～0.52之间;各试验土壤的细沟径流雷诺数在250～2 500之间,其流态介于层流与紊流的过渡范围,雷诺数随着放水流量的增大而迅速增大,流量在2～4L/min之间存在一个临界值,使得细沟径流由层流向紊流转化;各试验土壤在不同流量下的细沟径流佛汝德数在1.39～2.55之间,表明细沟径流均处于急流范畴;阻力系数在0.2～0.8之间,不同试验土壤在不同流量下的阻力系数差异很大,阻力系数与雷诺数没有明显的相关性。

5 experiment sites with five main arable soil types were chosen to conduct this experiment at the upstream of Yangtze River basin.It was analyzed the hydrodynamic characters of the rill runoff on the slope lands through the field artificial simulated runoff experiments.The experiment results indicate,velocity of the rill runoff would be increased with the increase of the discharge,and they are related by exponential function,with the index varying between 0.23 and 0.52.The Reynolds numbers of rill runoff vary between 250 and 2500,going up quickly with the increase of the discharge with the fluid state at the transition range between the laminar and turbulent.Meanwhile,there exists a critical value when the discharge is between 2 and 4L / min,that make the rill runoff transfer from laminar to turbulent.The rill runoff is turbulent under different surface discharge,with the Freud number changes between 1.39 and 2.55.Roughness coefficients vary enormously under different discharge for different soil mass,while they are between 0.2 and 0.8.On the other hand,the roughness coefficients have no obvious relationship with Reynolds numbers.