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Influences of pre-aerator angle variations on length of aerated cavity and pressure of stepped spillway
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摘要: 在宽尾墩+阶梯溢流坝+消力池一体化消能工中利用前置掺气坎连接WES曲面与阶梯溢流坝，能有效增加阶梯面掺气，避免阶梯遭受空化空蚀破坏。主要引用水气两相流VOF方法的RNG k-ε模型，采用几何重建方式对水气面附近进行插值以及利用PISO算法和非定常流算法进行数值模拟，模拟前置掺气坎角度8°，10°和11.3°时阶梯溢流坝上坎后掺气空腔长度及阶梯面压力分布，模拟范围从库区至消力池尾部。为验证模拟计算的可靠性，对阶梯溢流坝坎后掺气空腔进行模型试验，通过坎后空腔长度模拟值与实测值的对比分析，发现两者吻合较好，最大偏差为7.9%。模拟结果表明，掺气空腔长度随前置掺气坎角度的增加而增加，阶梯近壁面最大负压绝对值及压力随前置掺气坎角度的增加而增加且负压分布范围逐渐扩大。Abstract: Using a pre-aerator to connect WES curved surface with the stepped spillway in an integrative energy dissipater combination which includes flaring gate pier, stepped spillway and stilling basin can effectively increase the stepped surface aeration and protect stepped spillway from cavitation. The authors of this paper have utilized a RNG k-ε turbulence model and a water-vapor VOF model, made geometry reconstruction for interpolation, and used PISO and an unsteady algorithm to simulate the aerated cavity length and pressure distribution of the stepped spillway under the conditions of different pre-aerator angles of 8°, 10° and 11.3°; the simulation range is from the upstream reservoir to the downstream stilling basin. In order to verify the reliability of the numerical simulation, the model experiment of the stepped spillway for the aerated cavity was conducted. From analysis and comparison of the measured values and the simulated values of the aerated carity length, it is found that there is a small deviation between both values, and the maximum error is 7.9%. The numerical simulation results indicate that the aerated cavity length increases with the enlargement of the pre-aerator angle; the absolute values of the maximum negative pressures and shock pressures of the stepped surface increase with the augment of the pre-aerator angles; and the range of the negative pressure distribution is expanding gradually.
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Key words:
- engineering hydraulics /
- RNG k-ε model /
- 3-D numerical simulation /
- aerated cavity
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图 2 阶梯溢流坝坎后掺气空腔形态
Figure 2. Shapes of aerated cavity behind aerator on stepped spillway
图 3 阶梯水平及垂直近壁面平均压力沿程分布
Figure 3. Average pressure distribution on vertical and horizontal faces of steps
图 4 阶梯溢流坝阶梯负压等值线(单位：kPa)
Figure 4. Contours of negative pressure on stepped spillway (unit: kPa)
表 1 坎后掺气空腔长度实测值与模拟值
Table 1. Measured and simulated values of aerated cavity length behind aerator
方案 流量/(m3·(s·m)-1) 前置掺气坎角度/° 阶梯/个 坎后空腔长度/m 误差/% 空腔增长率/% 实测值 模拟值 实测值 模拟值 1 8 6.38 6.05 8.85 8.39 5.2 2 123.66 10 7.11 6.55 9.80 9.02 7.9 7.5 3 11.3 8.85 8.20 11.62 10.89 6.3 20.7 4 8 5.52 5.30 7.66 7.40 5.5 5 92.45 10 5.95 5.70 8.27 7.83 5.32 5.8 6 11.3 6.85 6.45 9.43 8.97 4.88 14.6 
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表 2 各方案阶梯水平及垂直固壁面负压值
Table 2. Negative pressure values on horizontal and vertical faceskPa
台阶 y/Y 方案1负压 方案2负压 方案3负压 x/X 方案1负压 方案2负压 方案3负压 第1级台阶 0 0 1.05 3.75 0 -3.52 -3.82 -4.42 0.036 -1.09 0 3.00 0.050 -3.58 -3.82 -4.42 0.072 -3.36 -1.52 0 0.075 -3.58 -3.82 -4.52 0.096 -3.97 -2.76 -4.12 0.100 -3.61 -3.82 -4.52 0.132 -3.82 -4.42 -5.20 0.125 -3.61 -3.82 -4.65 0.168 -3.80 -4.27 -5.03 0.150 -3.61 -3.82 -4.65 0.240 -3.66 -4.12 -4.73 0.175 -3.61 -3.97 -4.65 0.276 -3.57 -3.97 -4.58 0.200 -3.25 -3.36 -4.24 0.348 -3.54 -3.87 -4.48 0.225 -2.57 -2.42 -3.33 0.400 -3.52 -3.82 -4.42 0.250 0 -1.40 -2.15 注：Y表示前4级台阶垂直壁面高度之和，y表示到第1级台阶竖直顶点距离, 其中0~0.400为第1级阶梯垂直近壁面，0.401~0.600为第2级阶梯垂直近壁面，0.601~0.800为第3级阶梯垂直近壁面，0.801~1.000为第4级阶梯垂直近壁面。X表示前4级台阶水平壁面台步之和，x表示到第1级台阶水平顶点距离，0~0.25为第2级阶梯水平近壁面，0.26~0.50为第2级阶梯水平近壁面，0.51~0.75为第3级阶梯水平近壁面，0.76~1.00为第4级阶梯水平近壁面。
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