摘要
空化引起不同程度振动、冲击和噪声,加剧物体表面空蚀,使结构提早发生疲劳。为有效抑制和延缓空化发生和空泡脱落,该文提出了在水翼吸力面布置凹槽的方法,旨在通过水翼表面结构的改变来实现空化流动的调节。在数值模拟研究中,采用Realizablek-ε湍流模型和Schnerr-Sauer空化模型,围绕8°攻角下NACA66(MOD)水翼,开展不同空化数、凹槽尺度和凹槽位置对二维水翼空化流场的动力学特性研究,并进一步分析了水翼表面特殊结构抑制空化的机理。结果表明:当片空化发生时,凹槽布置在距水翼前缘0.32弦长位置时,能降低空泡振荡频率,提高水翼水动力性能;当云空化发生时,适当的凹槽表面构型能够使水翼吸力面边界层变薄,边界层分离点滞后,水翼尾缘回流区减薄,吸力面低压区减小,证明了凹槽表面构型对空化抑制的适用性。然而,在水翼吸力面布置凹槽,虽然可以降低水翼表面边界层的厚度,增强抗逆压能力,但却触发了凹槽附近区域回射流的加速。因此,只有当抗逆压梯度能力大于回射流冲击时,才可以实现对空化流动的抑制。该研究成果扩大了空化流动的被动控制方法研究范围,为水力机械空化抑制技术提供了参考。
The existence of cavitation will lead to different intensity of vibration,shocks as well as acoustic noise and worsen the cavitation erosions which results in structural fatigue failure.In order to suppress the evolution and detachment of bubbles efficiently,based on the existing experimental phenomena,a new idea is proposed to achieve cavitation flow control by setting pits on the suction side of the hydrofoil.To study the impact of this new structure on cavitation flow field,in this paper,the unsteady cavitation flow around the NACA66(MOD)hydrofoil at 8°angle of attack was simulated by Realizable k-εturbulence model combined with Schnerr-Sauer cavitation model for different cavitation numbers,pits size and pits location.The results indicate that the simulated cavity shapes around foil were well fitted with the experimental high speed images,and showed that the selected models can better predict the cavitation flow.The results also showed that for the study of the non-cavitation flow,the suction side pits led to the decrease of the hydrofoil lift-to-drag ratio and impair the hydrodynamic performance.However,this was very different from that in cavitation condition.In addition,the analysis of the dynamic characteristics of the 2D hydrofoil cavitation flow field and the effect of hydrofoil surface structure factors on cavitation suppression showed that the tail position of cavitation closure region was very close to that of the pits which located at 0.32 chord(0.32c)distance from leading edge for the sheet cavitation(Cavitation number=1.23).The presence of the pits changed the direction of the re-entrant jet and caused the severe dissipation of the kinetic energy of the re-entrant jet.As a result,the re-entrant jet was blocked to enter the cavity body,and therefore,the cavitation shedding and vibration frequency decreased.However,the evolution of cavity had not been suppressed along with the increased cavity length because local low pressure region formed at the position of pits(0.32c)celebrated the development
作者
王巍
唐滔
卢盛鹏
焦建雄
张庆典
王晓放
Wang Wei;Tang Tao;Lu Shengpeng;Jiao Jianxiong;Zhang Qingdian;Wang Xiaofang(Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education,Dalian University of Technology,Dalian 116024,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2019年第2期40-47,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金(51876022)
国家973计划项目(2015CB057301)
关键词
空化
计算机仿真
模型
水翼
吸力面凹槽
空化抑制
水动力性能
cavitation
computer simulation
models
hydrofoil
suction-side pit
cavitation suppression
hydrodynamic performance
