流动型态对曼宁糙率系数的影响研究

根据明渠水流流动型态的概念,通过对实验资料的分析,得到均匀流时糙率系数随水深增加而减小,形成M1型水面线的非均匀流时糙率系数随水深、水力坡度的增大而增大的规律。提出的糙率系数的二步计算法,可以解决因非均匀流水深沿程变化,难以建立糙率系数与水深关系的困难,为在水力计算中修正糙率系数提供了依据。

The Effects of Types of Flow on Manning's Roughness Coefficient

It is clearly that the roughness coefficient needs to be corrected in hydraulic calculations for open channel flow.Based on the concept of type of flow and experimental results,this paper shows that the roughness coefficient decreases with increasing of the depth of flow in an uniform flow,and increases with increasing of the depth of flow and energy gradient in non-uniform flow with M1water surface profile performed.In this paper,the two-steps method proposed to give an available method to determine roughness coefficient in non-uniform flow in which the depth of flow vary with distance,so it is difficult to establish a relationship between roughness coefficient and depth of flow.