绕水翼空化流动及振动特性的试验与数值模拟

Experiment and numerical simulation of vibration characteristics of hydrofoil in cavitating flow

采用试验与数值模拟相结合的方法,对不同材质水翼的空化水弹性响应及其振动特性进行了分析.试验中,采用高速摄像技术观测不同空化阶段的空穴形态,应用多普勒激光测振仪测量水翼的振动速度.采用k-ωSST湍流模型和Zwart空化模型对流场进行数值模拟,并建立两自由度结构模型,基于混合耦合算法实现流固耦合数值模拟计算.试验结果表明,水翼的振动幅度在云状空化阶段达到最大,水翼的振动主频与空泡脱落频率一致,并随空化数减小而降低.数值预测结果与试验结果吻合较好,能较准确地捕捉附着型空穴的生长、脉动以及云状空穴的断裂脱落过程,主要振动频率与相应空泡脱落频率一致.受水翼弹性变形和结构水弹性响应的影响,弹性材料水翼吸力面的空泡发展更为复杂,空泡脱落过程伴随着大尺度空泡团的二次附着与脱落,且空泡团容易发生破碎,形成水气混合状,其结构振动特性和流激振动频谱成分也更加复杂.

The unsteady cavitation behaviour and the corresponding cavity induced vibrations were in- vestigated. The high-speed camera and a single point laser Doppler vibrometer （LDV） are used to ana- lyze the transient cavitating flow structures and the corresponding structural vibration characteristics. The k - ω SST turbulence model with the turbulence viscosity correction and the Zwart cavitation model are introduced to the simulations. The fluid model is coupled with a chordwise rigid, two degrees-of- freedom system with the hybrid coupled fluid structure interaction model. The results show that the maximum vibration amplitude keeps relatively small for the inception cavitation and sheet cavitation, increases dramatically for the cloud cavitation and declines for the supercavitation. The main flow-in- duced frequency, which is in accord with the cavity shedding frequency, reduces with the decreasing of the cavitation number. Owing to the disturbance caused by the flow-induced flutter and deformation of the foil, it presents more complex cavitation patterns for the flexible hydrofoil, as well as more com- ponents in the vibration spectra.