基于拉格朗日方法的非定常空化流动研究

LAGRANGIAN-BASED INVESTIGATIONS ON UNSTEADY CAVITATING FLOWS

采用基于拉格朗日体系的有限时间李雅普诺夫指数、拉格朗日拟序结构和粒子追踪方法对绕水翼典型非定常云状空化流场进行研究。采用计算流体动力学方法获得空化流场数据数值,湍流模型采用经典大涡模拟方法,空化相变过程采用基于相间质量传输的Zwart模型进行处理。根据有限时间李雅普诺夫指数分布在空化核心区域定义了前缘拟序结构和尾缘拟序结构。在不同的空化发展阶段,两种拟序结构相互作用并呈现不同的分布规律,揭示不同空化发展阶段的典型流场结构。

Lagrangian-based methods are applied in this paper to get an insight into the transient sheet/cloud cavitating flows, including finite-time Lyapunov exponent （FTLE）, Lagrangian coherent structures （LCS） and particle trajectory. Computational Fluid Dynamics （CFD） is used to obtain the cavitation flow structures. The turbulence model utilizes the Large Eddy Simulation （LES） approach and the interface mass transformation is modeled using Zwart cavitation model. Detailed analysis of cavitating structures with the LCS defined by the ridges of the FTLE show two main LCSs in sheet/cloud cavitation region, which are defined as leading edge （LE-LCS） and trailing edge LCSs （TE-LCS） respectively. Different interactions between the two LCSs indicate different flow structures in different cavitating developing stages.