高水头阶梯溢流坝掺气坎体型优化试验研究

Experimental study on shape optimization of aerator of stepped spillway with high head

针对阶梯溢流坝前端设置掺气坎,以提高坝面减蚀能力与坝体消能率的研究理论尚不成熟的现状,通过9组不同掺气坎的水工模型试验,采用极差与方差分析方法得出了掺气坎角度与高度对阶梯溢流坝联合消能方式水力特性的显著性影响.试验结果表明:与掺气坎高度相比,坎角度对台阶面最大负压影响较大.掺气坎角度为11.3°,坎高度为1.0,1.3 m时,台阶面最大负压最小,分别为-9.25,-8.56 kPa;掺气坎角度对影响反弧段时均压强的显著性不如掺气坎高度,而两者对消力池最小时均压强的显著性影响相差不大.当掺气坎角度为11.3°,高度为0.7,1.0 m时,上游水流对下游的冲刷强度较小,水体掺气充分,反弧段最大时均压强分别为424.44,431.73 kPa;根据坝体消能效果,掺气坎高度是影响阶梯溢流坝消能率的主要因素.根据各因素综合分析,推荐掺气坎角度为11.3°,高度为1.0 m时为最优坎型,其消能率为53.63%.

The research theories for setting up an aerator in front of the stepped spillway to improve the dam surface erosion reduction capacity and the dam energy dissipation rate are still immature.Nine types of aerated concrete for hydraulic model tests,were adopted and the variance analysis and range analysis methods were used to obtain the significant influence of the different heights and angles aerated on the hydraulic characteristics of the stepped spillway.The experimental results show that compared with the height aerated,the angle has a great influence on the maximum negative pressure on the step surface.When the angle of aerator is 11.3°,the height of aerator is 1.0 m or 1.3 m,the maximum ne-gative pressure on the step surface is minimum,which is-9.25 kPa or-8.56 kPa respectively.Compared with the height aerated,the angle of aerator has a significant influence on the maximum time average pressure in the anti-arc section,but the effect of the different heights and angles on the minimum time average pressure in the stilling pool is similar.When the angle of aerator is 11.3°,the height is 0.7 m or 1.0 m,the upstream water flow has a lower scouring strength to the downstream floor,the water body is aerated sufficiently,and the maximum time average pressure in the anti-arc section is 424.44 kPa or 431.73 kPa respectively.For the energy dissipation effect of the dam,the height of aerator is the main factor affecting the energy dissipation rate of the stepped spillway.According to the comprehensive analysis of various factors,it is recommended that the aerator angle of 11.3°and the height of 1.0 m are the optimum aerator type,with an energy dissipation rate of 53.63%.