Abstract In order to find out the effect mechanism of the cavitation on the hump characteristic of pump-turbines, three dimensional numerical simulations with and without cavitation were carried out using the SST (shear stress transport) k-ω turbulence model and ZGB (Zwart-Gerber-Belamri) cavitation model. Numerical results agreed well with the performance characteristic and flow visualization results. Under cavitation conditions, the simulations with cavitation obtained a more accuracy prediction on the hump characteristic. The relationship between the performance characteristics and the cavitation was analyzed in details. A cavitation condition (cavitation coefficient is 0.14), under which the cavitation just occurs, was selected to investigate the hump characteristic. The occurrence position of the cavitation and the variation law with the cavitation coefficient were obtained. The hump characteristic is related to the cavitation on suction surfaces close to the leading edges of the blades at the runner inlet. The action mechanism of the cavitation on the change of the hump characteristic was revealed. The sudden increase of the cavitation in the hump region leads to the decrease in the Euler head and the increase in the hydraulic loss, resulting in the drop of the head. Detailed analyses reveal that the occurrence of the cavitation will block the runner passages, which reduces the working ability of the runner and induces large size vortices in the adjacent passages.

中文翻译：

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空化对水泵水轮机驼峰特性的影响机制

摘要 为了找出空化对水泵水轮机驼峰特性的影响机制，利用SST（剪切应力传递）k-ω湍流模型和ZGB（Zwart- Gerber-Belamri) 空化模型。数值结果与性能特征和流动可视化结果非常吻合。在空化条件下，空化模拟获得了对驼峰特性更准确的预测。详细分析了性能特征与气蚀之间的关系。选择空化条件（空化系数为 0.14），在该条件下空化刚刚发生，以研究驼峰特性。得到了空化的发生位置和空化系数随空化系数的变化规律。驼峰特征与靠近转轮入口处叶片前缘的吸力表面上的空化有关。揭示了空化对驼峰特性变化的作用机制。驼峰区空化的突然增加导致欧拉水头减小，水力损失增加，导致水头下降。详细分析表明，气蚀的发生会阻塞流道通道，降低流道的工作能力，并在相邻通道中引起大尺寸涡流。驼峰特征与靠近转轮入口处叶片前缘的吸力表面上的空化有关。揭示了空化对驼峰特性变化的作用机制。驼峰区空化的突然增加导致欧拉水头减小，水力损失增加，导致水头下降。详细分析表明，气蚀的发生会阻塞流道通道，降低流道的工作能力，并在相邻通道中引起大尺寸涡流。驼峰特性与靠近转轮入口处叶片前缘的吸力表面上的空化有关。揭示了空化对驼峰特性变化的作用机制。驼峰区空化的突然增加导致欧拉水头减小，水力损失增加，导致水头下降。详细分析表明，气蚀的发生会阻塞流道通道，降低流道的工作能力，并在相邻通道中引起大尺寸涡流。导致头部下垂。详细分析表明，气蚀的发生会阻塞流道通道，降低流道的工作能力，并在相邻通道中引起大尺寸涡流。导致头部下垂。详细分析表明，气蚀的发生会阻塞流道通道，降低流道的工作能力，并在相邻通道中引起大尺寸涡流。