泵站进水池吸入口涡旋结构及湍流特性的大涡模拟

Large Eddy Simulation of Vortex Structure and Turbulence Characteristics in Pump Sump

进水池是泵站工程的重要组成部分,其流态及水力特性对水泵性能有着重要的影响,不良的流态往往伴随着涡旋等水力现象的出现。采用流体体积(VOF)方法及大涡模拟(LES)对进水池中的流动和相关涡旋进行数值模拟,系统分析LES湍流模型所采用的网格,对网格进行收敛性验证,并将数值模拟结果与PIV实验结果进行比较,数值模拟结果与PIV实验结果吻合,说明本模拟方法可以用来进一步深入探讨二阶湍流参数。通过LES模拟结果对进水池中表面涡和底涡的形成和演化的基本机制进行探讨,揭示了涡旋周围的各向异性湍流结构以及动量的传递过程。

The pump sump is an important part of pump station. Its flow and hydraulic characteristics have an important impact on the performance of the pump. Poor flow patterns are often accompanied by hydraulic phenomena such as vortices. Vortices in the vicinity of pump intakes influence the pump performance with loss of efficiency and vibration. The vortex may appear in the pump sump, and the vortex is generally divided into free surface vortex and submerged vortex. Compared with most Reynolds averaged Navier Stokes (RANS) based simulations, large eddy simulation (LES) showed a better prediction for all kinds of vortices on location, shape, size of vortex core, velocity, as well as the turbulence kinetic energy inside vortex core. The LES results agreed with PIV results well. Based on the numerical results, time-averaged behavior of three typical vortices showed better similarities with reality that there was always a core region surrounding the axis where the azimuthal velocity stopped increasing and decreased to zero as radius went to zero. Besides, iso-surface of λ 2 was adopted to visualize the vortices. The volume of fluid model (VOF) and LES were used to simulate the vortices in the pump sump. The LES model, including the employed mesh was systematically analyzed and the numerical results were compared with the well-known published experiment with respect to the mean velocity and vorticity fields. Particular interests were paid to discover evolution of the free-surface and wall-attached vortices in term of their temporal and spatial characteristics. The anisotropic turbulence structure around the vortices were revealed as well as the momentum transport. The findings provided a deep insight into the application of LES in pump sump and the underlying mechanism of vortex formation and evolution in the sump.