下庄倒虹吸进出口水力特性水工模型试验研究

多管倒虹吸为引调水过程中的常用交叉建筑物,为使倒虹吸进口流态平稳,分水口通常不设置在倒虹吸进口附近。而下庄分水口由于征地和施工等原因,分水口与倒虹吸进口采取了合一布置,这对进口流态产生较大不利影响。基于水工模型试验,本研究提出的改无压明渠分水为有压短管分水口的方法极大改善了倒虹吸进口流态。而试验中发现下庄倒虹吸出口三个闸室在常遇工况下存在水面交替振荡现象,最大波幅达1.4 m,经过研究分析发现水流在检修闸门井和工作闸门井间的竖向扩散是造成振荡的原因,在检修门井和工作门井间设置隔梁或隔板可以抑制水流竖向扩散,从而减小了水面振荡,波幅减小至0.1 m,并且设置隔梁方案工程量相对较小,比较经济,故后续优化方案布置中采用该方案。研究成果可为类似工程的设计、研究和运行管理提供参考和借鉴。

Hydraulic Model Test on Hydraulic Properties at Inlet and Outlet of Xiazhuang Inverted Siphon

Multi-pipe inverted siphon is a common structure in water diversion projects. Outlets are usually kept a bit far away from the inverted siphon to keep the flow stable. However, due to difficulties in construction and land acquisition, the inverted siphon and lateral outlet at Xiazhuang are put together, posing adverse impact on flow pattern at the inlet. Based on physical modelling, a method of replacing pressure-free open channel outlet by pressurized tube outlet is proposed to minimize the impact of lateral outlet releasing and improving the flow pattern. Test reveal water surface oscillation with a maximum amplitude of 1.4 m at three downstream lock chambers under normal conditions. Analysis shows that the oscillation is induced by the vertical dispersion of flow between bulkhead gate shaft and working gate shaft. Arranging separating beam or slab could curb the vertical dispersion of flow, hence alleviating surface oscillation by reducing the amplitude to 0.1 m. Separating beam is recommended in future optimization as it is less costly in both engineering quantity and economy. The research findings offer reference for the design, research and operation management of similar projects.