坡面细沟侵蚀过程中的水动力特性变化

为定量揭示坡面细沟水流侵蚀过程中的水动力特征,开展不同流量(2 L/min,4 L/min,8 L/min)、不同坡度(5°,10°,15°,20°,25°)下的放水冲刷试验,对坡面细沟发育过程中的水动力学参数变化规律进行了研究。结果表明:在试验的流量和坡度范围内,平均流速随冲刷历时的延长和细沟形态的发展呈迅速递减—略有起伏—缓慢减小并最终趋于稳定的变化趋势,径流深随冲刷历时的增大而增大; 坡面细沟水流的雷诺数变化范围为237～1 090,在小流量时,雷诺数随冲刷历时增大而略有增大,在大流量时,雷诺数随冲刷历时增大而减小; 在整个冲刷过程中,弗劳德数始终大于1,表明该试验条件下的坡面流属于急流范畴; 坡面细沟水流的阻力系数随冲刷持续而增大; 弗劳德数随阻力系数的增大而减小,且具有良好的负向幂函数关系。该研究结果初步表明了土坡面的细沟侵蚀特征和水动力学特性,为土侵蚀动力学机制的进一步研究提供理论基础。

Variation of Hydrodynamic Characteristics in the Process of Rill Erosion on the Slope

This study aims to quantitatively study the hydrodynamic characteristics of rill flow.Three different flow discharges(2 L/min,4 L/min,8 L/min)and five slope gradients(5°,10°,15°,20°,25°)of controlled slope experiments were conducted.The results show that the average velocity decreases with the increase of scoring duration and the development of rill morphology;the runoff depth increases with the increase of scouring duration.The Reynolds number varies from 237 to 1090.At the large flow discharge,the Reynolds number decreases with the increase of scouring duration;by contrast,the small flow capacity increases.During the whole scouring process,the Froude number keeps greater than 1,indicating that the overland flow belongs to the category of jet stream.Darcy resistance coefficient of the slope rill flow increases with the continuously scouring,while the Froude number decreases with the increase of the Darcy-Weisbach resistance coefficient.A negative power function relationship is found between the resistance coefficient and the Froude number.