绕水翼空化流动及振动特性的试验与数值模拟
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摘要
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 investigated. The high-speed camera and a single point laser Doppler vibrometer( LDV) are used to analyze 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-offreedom 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-induced 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 deformationof the foil,it presents more complex cavitation patterns for the flexible hydrofoil,as well as more components in the vibration spectra.
The unsteady cavitation behaviour and the corresponding cavity induced vibrations were investigated. The high-speed camera and a single point laser Doppler vibrometer( LDV) are used to analyze 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-offreedom 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-induced 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 deformationof the foil,it presents more complex cavitation patterns for the flexible hydrofoil,as well as more components in the vibration spectra.
引文
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[3]陈喜阳,郭庆,孙建平,等.空化对离心泵低频水力振动影响的数值研究[J].华中科技大学学报(自然科学版),2014,42(6):6-11.CHEN Xiyang,GUO Qing,SUN Jianping,et al.Numerical study on effects of cavitations for centrifugal pump low frequency hydraulic vibration[J].Journal of Huazhong University of Science and Technology(natural science edition),2014,42(6):6-11.(in Chinese)
[4]顾巍,何友声,胡天群.轴对称体空泡流的噪声特性与空泡界面瞬态特征[J].上海交通大学学报,2000,34(8):1026-1030.GU Wei,HE Yousheng,HU Tianqun.Noise feature of cavitation flows on axisymmetric bodies and transient characteristics of cavity interface[J].Journal of Shanghai Jiaotong University,2000,34(8):1026-1030.(in Chinese)
[5]李忠,杨敏官,高波,等.空化诱发的轴流泵振动特性实验研究[J].工程热物理学报,2012,33(11):1888-1891.LI Zhong,YANG Minguan,GAO Bo,et al.Experimental study on vibration characteristics induced by cavitation of axial-flow pump[J].Journal of engineering thermophysics,2012,33(11):1888-1891.(in Chinese)
[6]KAWANAMI Y,KATO H,YAMAGUCHI H,et al.Mechanism and control of cloud cavitation[J].Journal of fluids engineering,1997,119(4):788-794.
[7]CHEN Guanghao,WANG Guoyu,HU Changli,et al.Combined experimental and computational investigation of cavitation evolution and excited pressure fluctuation in a convergent-divergent channel[J].International journal of multiphase flow,2015,72:133-140.
[8]HUANG Biao,WANG Guoyu,ZHAO Yu,et al.Physical and numerical investigation on transient cavitating flows[J].Science China(technological sciences),2013,56(9):2207-2218.
[9]WILLIAMSON C H K,GOVARDHAN R.Vortex-induced vibrations[J].Annual review of fluid mechanics,2004,36:413-455.
[10]胡敬彬.转动设备振动监测方法及案例分析[J].化工设备与管道,2004,51(2):48-52.HU Jingbin.Vibration monitoring method for rotating equipment and case analysis[J].Process equipment&piping,2014,51(2):48-52.(in Chinese)
[11]王文全,张立翔,闫妍,等.不同雷诺数下弹性薄板流激振动实验[J].北京工业大学学报,2012,38(1):55-59.WANG Wenquan,ZHANG Lixiang,YAN Yan,et al.Fluid-induced vibrations of thin elastic plate for different inflow Reynolds numbers[J].Journal of Beijing University of Technology,2012,38(1):55-59.(in Chinese)
[12]AUSONI P,FARHAT M,ESCALER X.Cavitation influence on Kármán vortex shedding and induced hydrofoil vibrations[J].Journal of fluids engineering,2007,129(8):966-973.
[13]WU Qin,HUANG Biao,WANG Guoyu,et al.Experimental and numerical investigation of hydroelastic response of a flexible hydrofoil in cavitating flow[J].International journal of multiphase flow,2015,74:19-33.
[14]MENTER F R.Improved two-equation k-ωturbulence models for aerodynamic flows[R].Washington,U S:NASA Technical Memorandum,1992.
[15]COUTIER-DELGOSHA O,FORTES-PATELLA R,REBOUD J L.Evaluation of the turbulence model influence on the numerical simulations of unsteady cavitations[J].Journal of fluids engineering,2003,125(1):38-45.
[16]HUANG Biao,DUCOIN A,YOUNG Yinlu.Evaluation of cavitation models for prediction of transient cavitating flows around a stationary and a pitching hydrofoil[C]//Proceedings of the 8th International Symposium on Cavitations.Singapore:Research Publishing Services,2012:601-608.
[17]THEODORSEN T.General theory of aerodynamic instability and the mechanism of flutter[R].Washington,U S:National Advisory Committee for Aeronautics,1935,496:291-311.