宽尾墩体型对阶梯溢流坝阶梯面掺气和消能的影响研究

宽尾墩与阶梯溢流坝结合的新型消能工,有效的解决了我国高坝泄洪建筑物由于高水头和大单宽流量等引起的高速水流问题。本文应用水汽两相流VOF模型和三维RNG-紊流模型,采用有限体积法进行区域离散,速度与压力的耦合方式采用PISO算法,利用几何重建格式的非恒定流迭代求解,对宽尾墩收缩比分别为0.7、0.445和0.4的Y型宽尾墩+阶梯溢流坝+消力池消能方式中阶梯面掺气特性和消能特性进行了数值模拟,模拟结果显示,各收缩比条件下,沿程平均掺气浓度略有波动,但总体呈减小趋势,随收缩比减小,阶梯面掺气范围减小。在前几级阶梯面,掺气充分,沿阶梯水平固壁面向外,掺气浓度呈先减小后增大的趋势,而沿阶梯垂直固壁面向下,掺气浓度先增大后减小,相同断面处平均掺气浓度随收缩比减小而增大。在掺气末端的阶梯面上,沿阶梯水平固壁面向外,掺气浓度逐渐增大,而沿阶梯垂直固壁面向下,掺气浓度逐渐减小,相同断面处平均掺气浓度随收缩比减小而减小。阶梯溢流坝消能率随宽尾墩收缩比的减小而增大。

Study on impact of flaring gate pier shapes on aeration and energy dissipation of stepped spillway

New energy dissipater of flaring gate pier combined with stepped spillway has effectively solved the problems of high-velocity flow caused by high working head and large unit discharge. This study applied a 3D flow model with RNG turbulence modeling, VOF water vapor two-phase modeling, and PISO algorithm for velocity-pressure coupling on FVM geometry reconstruction of iterative solution, to simulations of aerated flows over a stepped spillway and its energy dissipation behaviors. At the spillway entrance are Y-shape flaring gate piers and their contraction ratios of 0.7, 0.445 and 0.4 were examined and compared. The results show that under different contraction ratios of the piers the cross-sectional average of air concentration fluctuates with a decreasing global trend along the flow, and that the aerated regions over the steps are reduced when the contraction ratio is decreased. Over the initial several steps, the flow is full aerated and the mean air content at a fixed section is higher at a smaller contraction ratio. And the mean content near the top step faces takes an outward transverse trend of first decreasing then increasing from the center-line, while that near the vertical step faces takes a downward trend of first increasing then decreasing. Over the steps near the spillway outlet, the mean air content at a fixed section is lower at a smaller contraction ratio. And the mean content near the top step faces increases outward, while that near the vertical step faces decreases downward. The energy dissipation rate of this stepped spillway is increased with a decreasing contraction ratio of the Y-shape flaring gate piers.