河渠弯道缓流水面曲线计算探讨

Computation of water surface curve of slow flow in meandering river channel

明渠与河道中的弯道水流多为缓流,生产实践部门或因技术欠缺,或因嫌其复杂,常常忽略或不考虑弯道的水流特点,从而可能导致弯道水面线计算成果出现较大误差.本文导出了弯道缓流的纵向和横向水面曲线计算式,提出了纵向水面线的简易计算方法.通过计算实例比较了有无考虑弯道水流特点所导致的结果差异,分析了水流缓急程度、弯道弯曲程度等对纵向和横向水面曲线计算结果的影响.结果表明,相同弯道出口水位,有无考虑局部水头损失所计算的弯道入口水位差异,与水流缓急状况有显著的正相关关系,而与曲率的正相关关系不显著;弯道最大横向水面超高值与水流缓急状况和弯道弯曲程度均密切相关.

In the open canal and river, the most of water flow in the meandering channel is slow flow. Owing to lack of technology or computational complexity, it is very likely to cause a big error in the computing result of water surface line in curving watercourse because of neglecting or ignoring the characteristic of slow flow in the meandering channel. This thesis educes the computation formula for lengthways and transverse water surface lines of slow flow in the meandering channel, and introduces a simple computating method of lengthways water surface line. Moreover, by examples, the thesis compares the results of lengthways water surface line considering and neglecting the characteristic of slow flow in the meandering channel, and analyzes how the water flowing speed and the bend degree of the meandering channel influence the lengthways and transverse water surface line. It is concluded that for the same outlet water line of the meandering channel, the difference of inlet water line computated by considering or not considering the local loss of water energy has remarkable postive correlativity with water flowing speed, but just a little with the bend degree of the meandering channel; and the maximum transverse water superelevation is highly interrelated with both water flowing speed and the bend degree of the meandering channel.