回射流强度对水翼表面空化形态的影响

Influence of re-entrant jet strength on cavitation characteristics of hydrofoil

为了研究空化发生时翼型上表面的回射流对空化体形态特征和周期性演化规律的影响,建立了不同迎流角下的绕二维水翼流场模型,采用CFD数值模拟方法分析了发生空化时的流场压力、速度和相态分布特点;采用RNG k-ε湍流模型和Schnerr-Sauer空化模型对二维水翼空化流动进行了非定常数值计算.分析了空化数为0.91,迎流角分别为4°,10°,12°时,当空化发生时回射流运动特征以及回射流对于空化产生和发展的影响规律,并基于回射流的速度和特征长度等因素,提出采用量纲一的特征数用于描述回射流的强度,分析发现回射流强度是空化体形态改变的重要因素,并提出了空化形态改变的判断依据.结果发现,当特征数处于不同数量级时,对应空泡体的不同周期性阶段;同时,特征数的大小对应不同空泡体类型.

In order to investigate influences of re-entrant jet strength on periodical evolution of cavity attaching to the upper surface of a hydrofoil,several 2D meshes around a hydrofoil at different inflow angles are established. The distributions of pressure,velocity and phase features of cavitating flow field are analyzed by using CFD method. Unsteady cavitating flows over the 2D hydrofoil with different inflow angles are simulated with the RNG k- ε turbulence model and Schnerr- Sauer cavitation model.The re-entrant jet motion features and interaction with cavity are analyzed at 4°,10° and 12° inflow angles and 0. 91 cavitation number. Based on velocity,characteristic length and other parameters,a critical cavitation number is put forward to estimate the strength of re-entrant jet and serves a basis of judgment on change in cavity shape. The results show that the strength of re-entrant jet is an important factor influencing the structure of cavity. It is identified that the magnitude of criterial number can be correlated to different periodical stages and types of cavity.