典型双孔渡槽复杂流态的改善研究

Improving complex flow patterns in a typical double-hole aqueduct

为减轻渡槽在大流量运行时出现的水位波动较大、紊流和涡流等复杂流态问题,选取典型双孔渡槽模型进行水力学模型试验和三维数值模拟,应用物理模型与数值模拟相结合的方法研究渡槽出口的卡门涡街在被边界约束时对其上游产生的波浪回涌现象,通过机理解析提出“纺锤型”导流墩方案。研究发现,卡门涡街脱落频率与上游回涌波浪频率一致。边界约束下卡门涡街对上游流态影响机理为:涡街交替脱落产生横向的交变作用力,在边界约束下局部阻水进而形成波动并向上游传递,随着涡街的交替脱落,上游形成波浪交替回涌现象。施加“纺锤型”导流墩后,进出口流态得到改善,能大幅减轻涡街强度和对上游流态的影响,槽身最大波幅消减度达到80%以上。对比不同长度导流墩组合试验后,提出进、出口导流墩纵横比分别为1.5、2.0的最佳组合。

To mitigate abnormal flow patterns,such as significant water level fluctuations,turbulence,and eddy currents in high-flow scenarios,a hydraulic model experiment and three-dimensional numerical simulation were conducted using a typical double-hole aqueduct model.The aim was to investigate the wave surge phenomenon caused by the Karman vortex street at the aqueduct's outlet when constrained by the boundary.By employing both physical model experimentation and numerical simulation,a “spindle type” diversion pier concept was developed based on the observed mechanism.The study revealed a consistent shedding frequency between the Karman vortex street and the upstream surge wave frequency.Under boundary constraints,the Karman vortex street's alternating shedding generated transverse alternating forces.These forces,combined with localized water blockages,induced wave transmission to the upstream region.Consequently,the upstream wave exhibited alternating patterns in response to the vortex street's shedding.Implementing the “spindle type” diversion pier resulted in improved flow patterns at the inlet and outlet,significantly reducing the strength of the vortex street and its impact on the upstream flow pattern.Notably,the maximum amplitude reduction of the trough body exceeded 80%.Based on the results from a comparative test involving different lengths of diversion piers,the combination that offers the optimal balance between performance and cost-effectiveness is recommended.This combination consists of inlet and outlet diversion piers with an aspect ratio A_R=L/W of 1.5,2.0,respectively.