阻力形式对坡面流流速修正系数的影响

Effects of Resistance Forms on Velocity Correction Factor of Overland Flow

坡面流平均流速是建立坡面土壤侵蚀过程模型的基础参数,主要通过示踪法测定的水流表层流速乘以修正系数α获得,因此对α的合理取值是准确计算平均流速的关键。在收集和整理前人试验资料的基础上,利用室内水槽冲刷试验,研究了不同阻力形式(颗粒阻力、输沙阻力、植被阻力)对坡面流流速修正系数的影响。结果表明:坡面流流速修正系数随颗粒阻力、输沙阻力增加而减小,随植被阻力增加而增大,两者均可用幂函数表示;不同阻力形式主要通过改变坡面流流速分布影响流速修正系数,颗粒阻力和输沙阻力主要使流速梯度变大,而植被阻力主要使流速梯度变小。利用逐步回归分析给出了多种阻力形式作用下流速修正系数的预测公式,与实测值对比,吻合较好。

Mean flow velocity is one of the most important hydraulic variables in soil erosion modeling, which is normally estimated by multiplying surface velocity of flow with a correction factor （α）. So a reasonable α value is imperative for precise estimation of mean flow velocity. The effects of grain resistance, transport resistance and vegetation resistance on correction factor α were investigated through indoor scouring experiment on the basis of the datasets collecting from the literature. The results showed that α decreased as grain resistance, transport resistance increased and increased as vegetation resistance increased. The effects of different resistance forms on α were mainly achieved by changing the velocity profile of overland flow. The grain resistance and transport resistance made the velocity profiles steeper, while the vegetation resistance made the velocity profiles gentler. The prediction equation of α under various forms of resistance was proposed by using stepwise regression analysis and the predicted values agreed well with the measured ones.