前置突扩突跌掺气设施曲线阶梯水流掺气特性数值计算

Numerical calculation of aerated flow characteristics in a curve-floor stepped tunnel with pre-sudden lateral enlargement and bottom drop aerator

采用Realizable k-ε紊流模型和水气两相流Mixture模型对不同流量下前置突扩突跌掺气设施曲线阶梯连接段水流进行了数值模拟,得到了连接段边墙、底板及水流内部掺气量分布规律。结果表明:突扩突跌掺气设施形成的掺气空腔长度和形态与试验结果吻合,测点处掺气量的计算值大于试验值,但计算值与试验值随流量增大而增大的变化规律基本一致;在单宽流量大于28 m^(2)/s时,水流通过突扩突跌掺气设施后均能形成稳定的侧空腔和底空腔;在流经阶梯段过程中,掺气作用逐渐从四周向内部发展,最后形成均匀的掺气水流;连接段突扩突跌掺气设施和阶梯的联合作用能够有效地提高水流在底板和边墙处的掺气量;在单宽流量为54 m^(2)/s时,连接段末端掺气均匀水流的掺气量高达20%。通过设置前置突扩突跌掺气设施,能有效提高大单宽流量阶梯水流掺气量,降低泄洪建筑物产生空蚀破坏的风险。

Using the realizable k-εturbulence model and the water-gas two-phase flow mixing model,the flow in a curve-floor stepped tunnel with pre-sudden lateral enlargement and bottom drop aerator under different flow rates was numerically simulated,and the distribution rule of aeration concentration in the side wall,bottom plate and flow of the curve-floor stepped tunnel was obtained.The results show that the cavity created by the pre-sudden lateral enlargement and bottom drop aerator is consistent with the test results.The calculated value of the aeration concentration at the measurement point is greater than the test value,but however,the calculated and measured values both increase with the discharge.When the discharge per unit width is greater than 28 m^(2)/s,stable side and bottom cavities through sudden lateral enlargement and bottom drop aerator can be formed.During the flow passing through the step,the aeration effect gradually develops from the surroundings to the inside,and finally a uniform aeration water flow is formed.The joint effect of the sudden lateral enlargement and bottom drop aerator and stairs in the connection section can effectively increase the aeration concentration of the water flow at the bottom and side walls.When the discharge per unit width is 54 m^(2)/s,the aeration concentration of the aeration uniform water flow at the end of the connection section can reach 20%.The provision of pre-sudden lateral enlargement and bottom drop aerator can effectively increase the aeration concentration of the ladder energy dissipator under large discharge per unit width,and can reduce the risk of cavitation damage in flood discharge structures.