垂直梯形闸门自由出流水力特性试验研究

Study on the hydraulics of vertical trapezoidal sluice gate under free flow conditions

垂直梯形闸门是一种新型平板闸门,与常规矩形闸门相比,因其不需修建闸室和扭面等附属建筑物,占地小,在灌区各级梯形渠道控流和分流应用方面具有优势。梯形闸门的过流边界条件特殊,与矩形闸门过流水力特性明显不同。为明晰其水力特性,在边坡系数为1.5、1.75和2的典型梯形渠道上开展了186组模型试验,重点分析了闸门开度e、闸前水深H 0等参数对闸后流态和流量的影响,并基于试验数据研究了梯形闸门自由出流时的流量计算方法。结果表明,水流经梯形闸门左、中、右孔口流出的三股水流在闸后碰撞,水面宽收缩至最小,中轴线及其附近水深最大,横向水面轮廓呈“驼峰”状,且驼峰出现的位置和水流碰撞引起的水面波动幅度与闸门开度、闸前水深有关。当流量和闸门相对开度分别增大1倍时,驼峰距闸门的距离分别由3.6 e、8.2 e变化为6.0 e、3.3 e,驼峰高度由1.5 e、3.0 e变化为2.4 e、1.5 e,驼峰下游渠道水流趋于均匀分布所需要的距离由15.0 e、33.0 e变化为34.0 e、17.0 e。收缩水流在势能和动能相互转化作用下沿横向和纵向扩散,能量沿程耗散,水面波动减小直至与渠道水面衔接。流量系数公式相对误差平均值为2.17%,其中相对误差小于6%的数据占比为96.3%,总体精度较好。研究成果可为垂直梯形闸门的工程设计和运行管理提供参考。

Vertical trapezoidal gate is a new type of flat gate,which has advantages over conventional rectangular gates in flow control and diversion applications in irrigation areas at all levels of trapezoidal channels because it does not need to build auxiliary buildings such as gate chambers and torsion surfaces and occupies a smaller area.The overflow boundary conditions of trapezoidal gates are different from those of rectangular gates,in this study,a total of 186 tests were conducted for studying the hydraulic performance of the trapezoidal-shaped sluice gates built in the trapezoidal canals with side slopes of 1.5,1.75 and 2,respectively.The effects of parameters such as gate opening e and water depth in front of the gate H 0 on the flow pattern and discharge after the gate were analyzed,and the discharge calculation method for free outflow of trapezoidal gates was studied based on the test data.The results indicated that the outlet flow through the gate were divided into three jets.The collision of the jets forms a hump,which results in a contracted cross-section with the smallest water surface width,the largest water depth at the centerline.When the discharge and the relative opening of the gate are doubled respectively,the distance of the hump from the gate changes from 3.6 e and 8.2 e to 6.0 e and 3.3 e,and the height of the hump changes from 1.5 e and 3.0 e to 2.4 e and 1.5 e,and the distance required for the water flow in the channel downstream of the hump to be evenly distributed changes from 15.0 e and 33.0 e to 34.0 e and 17.0 e.The flow exhibited wavy appearance with alternate contraction and expansion in streamwise and width direction due to the interchange between kinetic and potential energies,and the fluctuation decreased with the dissipation of total energy.The average relative error of the flow coefficient formula obtained was 2.17%,and the data with relative errors less than 6%accounted for 96.3%.The results can provide reference for the engineering design and operation management of trapezoidal sluice gate in practice.