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对巨亭水电站泄水建筑物下游局部冲刷过程进行了二维数值模拟。采用RNG k-ε湍流模型封闭N-S方程、有限体积法在计算网格上离散求解、VOF方法追踪自由水面;采用C语言编写用户自定义函数,以泥沙起动切应力作为床面泥沙起动判别标准,通过分析比较水流剪切力与泥沙起动切应力大小,用以控制冲刷坑底部边界变化;采用局部重构模型和弹簧光顺模型更新计算区域和网格质量,藉以模拟和追踪局部冲刷坑边界变化。研究表明,模拟结果与实测资料符合良好。在冲刷坑的冲刷过程中,床面剪切应力随着冲刷的进程急剧减小,湍动能随着冲刷的进程减小缓慢;床面剪切应力和湍动能沿程变化均较为剧烈,床面剪切应力沿程先增大后减小,床面湍动能则沿程减小。冲刷坑的纵向平衡形态或床面泥沙起动主要决定于床面剪切应力,床面湍动能对泥沙起动也具有重要影响。
The two-dimensional numerical simulation of the local scouring process downstream of the drainage structure of Junting Hydropower Station was carried out. The NS equations were closed by the RNG k-ε turbulence model. The finite volume method was discretized on the computational grid. The VOF method was used to track the free surface. The C language was used to write a user-defined function to determine the initial sediment stress Standard to analyze the shear stress of the flow and the initial shear stress of the sediment for the purpose of controlling the change of the bottom boundary of the scour pit. The local reconstruction model and the spring smooth model are used to update the calculation area and the grid quality so as to simulate and track the local scour Pit boundaries change. The research shows that the simulation results are in good agreement with the measured data. During the scouring process of scour pits, the bed shear stress decreases sharply with the process of scouring, and the turbulent kinetic energy decreases slowly with the scouring process. The changes of bed shear stress and turbulent kinetic energy are all dramatic, The shear stress first increases and then decreases, while the bed turbulence kinetic energy decreases along the course. Longitudinal balance of scour pit or bed sediment start mainly depends on bed shear stress, bed turbulence kinetic energy also has an important impact on sediment start.