圆孔格栅不同开孔率对井式消能水力特性的影响研究

Study on Influence of Different Opening Ratios of Round-hole Grid on Hydraulic Characteristics of Well-type Energy Dissipation

对于山区消能建筑物而言,在地形地质条件受限时,圆形消力井是一种可行的选择,其井深和井径的大小直接影响到工程投资和消能效果。通过水工模型试验,研究格栅开孔率变化对消力井底板时均压强、脉动压强标准差、脉动压强峰峰值等水力特性的影响。成果表明:①当格栅开孔率为40%时,消力井尾水渠水流流态较为平顺,但格栅下部水体紊动剧烈,消力井底板射流水股落点附近水流脉动压强时均值、标准差等均最大;②格栅开孔率降低至35%时,格栅上部水体和尾水渠水流流态紊动稍有增强,但格栅下部水体紊动程度减弱,水股落点附近水流脉动压强时均值、标准差均有所降低;③格栅开孔率进一步减小至30%时,入射水流在格栅上部的弹射现象加剧,导致尾水渠流态极为紊乱,虽然消力井底板时均压强、脉动压强标准差继续降低,但降幅明显减小,趋于稳定。

For energy dissipation buildings in mountainous areas, the circular baffle well is a feasible choice in case of limited topographic and geological conditions. The depth and diameter of the well directly affect the investment and energy dissipation effect of the project. A hydraulic model testis conducted to study the influence of changes in opening ratio of the grid on hydraulic characteristics such as the time-averaged pressure of the bottom plate of the baffle well, the standard deviation of pulsating pressure and the peak value of pulsating pressure. The results show that when the opening ratio of the grid is 40%, the flow pattern of the tailrace is relatively smooth, but the water body is strong turbulent in the lower part of the grid, and the jet stream time-averaged and standard deviation value of the pulsation pressure near the falling point is the highest in the bottom. When the opening ratio of the grid is reduced to 35%, the turbulent degree of the grid’s upper water body and the tailrace is slightly enhanced, but the turbulence degree of the grid’s lower water body is weakened, and time-averaged and standard deviation value of the pulsation pressure near the falling point of the water flow are lowered. When the opening ratio of the grid is further reduced to 30%, the ejection phenomenon of the incident flow in the upper part of the grill intensifies, resulting in a very disordered flow pattern of the tailrace. Although the time-averaged pressure and the pulsating pressure standard deviation of the bottom plate of the baffle well continue to decrease, but the decrease reduces significantly and stabilizes.