复式河槽正常水深计算方法比较

明渠恒定均匀流正常水深在水力计算中十分重要。而对于复式河槽,当洪水漫滩后,直接运用曼宁方程推求正常水深,将带来很大误差。系统地总结了计算正常水深的各种方法,用二分法求解,并运用英国科学工程研究协会洪水水槽设施(SERC-FCF)的大量系列水槽实验成果加以比较。比较发现,精度由高到低依次为COHM方法、刘沛清法、断面倾斜分割法、动量传递法、谢汉祥法、断面叠加法。通过对各种方法详细分析,建议在计算天然复式河槽正常水深时,COHM方法是值得推广的一种好方法。

Comparison of methods predicting normal depth in compound channels

The normal depth plays an important role in hydraulic calculation. To a compound channel, when water in a main channel flows in an out-of-bank condition and onto the adjoining flood plain, it results in great error if the normal depth is calculated by the Manning equation. All kinds of methods predicting the normal depth in compound channels are systemically summarized in this paper. In all the methods, the normal depth is solved by the dichotomy method and compared with different series of experimental data from Engineering Research Council Flood Channel Facility. By comparison, it is found that the calculation precision is high with the methods considering momentum exchange between the main channel and the floodplain. According to the order from high precision to low, they are, in turn, the channel coherence method, the Liu Peiqing's method, the cross-sectional inclined division method, the momentum transfer method, the Xie Han-xiang's method, and the superposing cross section method. By analyzing the advanteges and disadvantages of the methods mentioned above, it is pointed out that the channel coherence method is a good method in calculating the normal depth in natural rivers with compound cross section.