南水北调典型宽浅渠道糙率系数研究

Research on the absolute roughness of the typical channel of the south-to-north water diversion project

南水北调中线工程的平均水力坡降只有0.078‰,所以正确估算输水渠道的水力损失非常重要。中线输水渠道的流态主要位于紊流过渡区,且接近粗糙区,其水力半径R=4～5m。国内缺乏如此大水力半径的渠道糙率n值的观测资料,模型试验又将面临水流非粗糙区的相似率问题。本文按粗糙区设计模型,近似推求中线干渠的n值及其变化规律,近似构造出过渡区的n值计算关系,并与已有公式比较,说明其合理性。

The average hydraulic slop of the middle route project of south-to-north water diversion is only 0.078‰. So it is very important to estimate the head loss of the open channel correctly. The flow pattern in the open channel lies at the turbulent intermediate zone. It is adjacent to the the turbulent rough zone. The radius of the channel varies from 4 to 5 meters. The domestic observation data which involves the big radius is scare. If it is resorted to the model experiment, the problem concerning the non-rough zone is difficult to solve. This essay designs the model approximately according to the rough zone decipline. The narrator deduces the law of the roughness of the channel approximately and constitutes the possible equation deciding the roughness. Moreover, the narrator contrasts the equation with the existing equations and concludes it is feasible practically.