绕水翼空泡脱落及其空化脉动特性

为改善水力机械抗空化性能,采用数值模拟与试验相结合的方法对NACA0015水翼非定常云空泡脱落机理进行研究,分析不同空化阶段下非定常空泡结构对翼型表面产生的空化脉动规律,探讨空化非定常过程中压力脉动产生的主要原因.结果表明:基于密度分域滤波器的湍流模型(FBDCM)能较好地模拟水翼表面空泡周期性脱落的非定常过程;在攻角为8°,空化数为1.25的工况下,空泡演化的非定常过程主要分为3个阶段,分别为附着型空泡形成与生长阶段、附着型空泡脱落与云空化形成阶段和云状空泡发展与溃灭阶段;在第二阶段结束时,空泡体积分数增至该周期内最大值;在第三阶段,由于空泡在翼型表面逐渐脱落并溃灭,翼型表面的压力水平逐渐回升,且回射流是空泡脱落的主要原因.

Cavitation shedding and cavitation fluctuation characteristics around hydrofoil

To improve the resistance cavitation performance of hydraulic machinery, the mechanism of unsteady cloud cavitation shedding around the NACA0015 hydrofoil was studied by combining numerical simulation and experimental method. The cavitation fluctuation caused by the unsteady cavitation structure on the hydrofoil surface under different cavitation stages was analyzed, and the main reasons for pressure fluctuation during the unsteady process of cavitation were discussed. The results demonstrated that the FBDCM turbulence model could accurately simulate the unsteady process of periodic shedding of cavitation on hydrofoil surface. Under the condition of the attack angle was 8° and the cavitation number was 1.25,the unsteady process of cavitation evolution can be divided into three stages: formation and growth of attached cavitations, shedding of the attached cavitation and formation of cloud cavitation, the stage of development and collapse of cloud cavitation. At the end of the second stage, the cavitation volume fraction increases to the maximum during the period. In the third stage, the pressure level on the hydrofoil surface gradually rises due to the collapse of the cavitation shedding pattern on the hydrofoil surface, and the main reason for the cavitation shedding was the re-entrant jet flow.