洞内消能即在隧洞内布置消能工,可优化枢纽布置、降低造价,在引调水工程中应用较为广泛。然而洞内消能水流流态复杂,理论性计算无法满足设计要求。以某灌区渠首引水隧洞洞内消能工为研究对象,通过大比尺水工模型试验,验证渠首引水隧洞洞内消能设计参数的合理性;并通过优化试验,提出适用于洞内消能的“消力池+消波梁”组合消能布置型式,解决洞内波浪高、洞顶余幅不足、空蚀空化等问题。研究结果表明:①无压洞内最大波浪高度减小67%,洞顶余幅可满足安全输水条件;②工作闸门后底板堰面曲线段和边墙扩散段局部最小水流空化数约0.37,堰面出现空蚀空化的可能性较低;③消力池底板沿程测点水流脉动压力均方根均未超过1.0×9.81 kPa,满足结构设计要求。与传统下沉式消能工相比,本文提出的“消力池+消波梁”组合消能型式消能效率显著提高,具有更好的消能特性,水工模型试验验证了优化方案的可行性。消能方案对于解决类似工程洞内水面波动大、难以满足洞顶安全余幅的问题效果显著,消波梁作为洞内消能工,对隧洞过流能力几乎不构成影响,具有一定的普适性。研究成果可为大型灌区渠首消能设计提供参考和借鉴。

[Objective] The flow patterns of energy dissipation inside tunnels are complex, and theoretical calculations cannot meet design requirements. This research aims to: (1) verify the rationality of design parameters for energy dissipation in diversion tunnels at canal head based on hydraulic model tests; (2) propose an energy dissipation layout suitable for specific projects through model optimization to address high wave height inside the tunnel, insufficient clearance below the tunnel crown, and cavitation and erosion. [Methods] A hydraulic model test with a scale of 1∶1.5 was selected to simulate the diversion channel, pressurized tunnel, in-tunnel gate chamber, energy dissipation section, and a downstream section of free-flow tunnel. Additionally, an emergency gate shaft and the ventilation pipe behind the gate were simulated. A water tank was used as the model reservoir. The project involved three different discharge conditions, each with varying reservoir water levels, resulting in eight typical working conditions for testing. Then, based on the hydraulic model test results under different conditions, the downstream flow pressure characteristics, cavitation characteristics of the weir surface behind the operating gate, pressure characteristics of the gradually expanding stilling basin floor and sidewalls, flow connection patterns, and energy dissipation performance were obtained. Finally, the dimensions of the stilling basin section and the free-flow tunnel were improved, and wave suppression measures were optimized based on the test results. [Results] The hydraulic model test revealed shortcomings in the original energy dissipation scheme and proposed a combined layout of “stilling basin + wave suppression beam” suitable for in-tunnel energy dissipation. The test results showed: 1) the maximum wave height inside the free-flow tunnel was reduced by 67%, and the tunnel crown clearance met safe water conveyance requirements; 2) The local minimum cavitation number of the water flow at the curved section of the weir surface and the expanded section of the sidewalls behind the operating gate was about 0.37, indicating a low likelihood of cavitation erosion; 3) The root mean square of fluctuating pressure at measuring points along the stilling basin floor did not exceed 1.0×9.81 kPa, meeting structural design requirements. [Conclusion] This study proposes a combined energy dissipation method of “stilling basin + wave suppression beam” to address problems of high wave height and insufficient tunnel crown clearance in the original scheme. Compared with traditional submerged energy dissipators, the combined method significantly improves dissipation efficiency and has better energy dissipation characteristics. Hydraulic model tests verify the feasibility of the optimized scheme. The energy dissipation scheme is effective in solving the problems of large waves and insufficient tunnel crown clearance in similar projects. It is effective under multiple reservoir water levels and discharge conditions, and the wave suppression beam, as an in-tunnel energy dissipation structure, has little impact on tunnel flow capacity, demonstrating certain universality.