地表粗糙度对坡面流水动力学参数的影响

Influences of surface roughness on overland flow hydraulic characteristics

坡面流阻力的研究对于深入认识坡面流水力特性及土壤侵蚀产沙机理具有重要意义。采用变坡试验水槽,利用定床阻力冲刷试验系统研究了坡面流Darcy-Weisbach阻力系数与粗糙度、流量、坡度和水流型态之间的关系。结果表明:阻力系数随着床面粗糙度的增加呈指数函数增大;阻力系数随着雷诺数的增加呈幂函数减小,且随粗糙度的增加;阻力系数与弗劳德数呈良好幂函数关系,且粗糙度的影响不显著,流量为主要影响因素;人工模拟粗糙度床面下,阻力系数可由粗糙度、流量和坡度的简单幂函数良好表示,并且粗糙度为主要影响因素,流量和坡度的影响相对较小。由因子分析可知,阻力系数可由粗糙度和弗劳德数良好表示,经检验该模型可用来计算不同粗糙度坡面薄层水流的阻力系数。

Exploring overland flow resistance is important for understanding the flow hydraulic characteristics, soil erosion and mechanism of sediment yield on sloping land. This study systemically discussed the relation- ship between Darcy-Weisbach resistance coefficient of overland flow and surface roughness, discharge, slope gradient as well as flow pattern through the fixed-bed model test. Results showed： with the simulated surface roughness increasing, the resistance coefficient exponentially increased. The relationship between resistance coefficient and Reynolds number was negative, which firstly increased and then decreased with surface rough- ness increasing. The relationship between resistance eoefficient and Froude number presented a power func- tion ; moreover, surface roughness is an insignificant factor and discharge is the dominant influence. Under the bed with artificial simulation of surface roughness, resistance coefficient could expressed by surface roughness, discharge and slope with a simple power function. Resistance coefficient was significantly affected by surface roughness, but less affected by discharge and slope. Resistance coefficient could expressed well by surface roughness and Froude number based on all influence factors by factor analysis, this formula can be used to predict the resistance coefficient of overland flow with different surface roughness.