超高水头大泄量竖井旋流泄洪洞的数值模拟研究

Numerical simulation study on vortex shaft spillway with superhigh water head and large flood discharge

为了克服传统模型试验对竖井旋流泄洪洞复杂水力特性测试的局限性,本文基于VOF法采用Realizable k-ε双方程紊流模型,对某一超高水头、大泄量竖井旋流泄洪洞进行数值模拟,得到了水流流态、空腔直径、压强及旋流角等水力要素的分布规律,由模拟结果分析得出:竖井内旋转水流的水层厚度分布不均,主流水体,水层较厚,非主流水体,水层相对较薄。旋转水流切向流速的衰减梯度从上到下逐渐降低;在竖井前半段,轴向流速随竖井高度的降低增加较快,竖井中下段,主流水体的轴向流速增加明显,而非主流水体增加缓慢。利用试验测试数据对计算结果进行对比验证,结果表明计算值与实测值吻合良好,说明数值模拟方法可行。

A realizable k-ε two-equation model for turbulent flow and a VOF method were adopted in the present study to simulate the flows in a vortex shaft spillway that has super-high working heads and large flow capacity, and the simulated flow pattern, cavity radius, pressure distribution, free water surface profile, rotational angle and other characteristics of the flows were examined. The results indicate that rotating flows in this vortex shaft have an uneven distribution in thickness of the water layer on the shaft wall, with greater thickness in the mainstream area. The gradient of stream-wise attenuation in tangential velocity of the rotating flows is gradually reduced from top to bottom. In the upper part of the shaft, axial velocity increases rapidly with the decreasing potential energy. When the flow reaches the middle and lower part, its axial velocity keeps increasing rapidly in the mainstream area, but the increase is significantly slowed down in the other area. Comparison of the numerical simulations with the measurements on a scale model shows a satisfactory agreement and the reliability of the method adopted.