空化水动力学非定常特性研究进展及展望

空化作为一种重要的复杂水动力学现象,具有明显的三维流动特征与剧烈的非定常特性,在水力机械、船舶推进器、水利工程中广泛存在,且通常会带来不利的影响,长期以来一直是水动力学领域研究的重点与难点课题之一.本文首先从实验测量和数值模拟两个角度,综述了空化水动力学非定常特性研究的发展概况, 分析了当前存在的问题.在空化实验研究中,主要介绍了空化水洞、空化流场测量以及多物理场同步测量等方面所取得的进展.在数值模拟方法中, 对目前的空化模型和湍流模型进行了分类介绍,并重点讨论了大涡模拟、验证和确认等在空化流模拟中的应用.之后以附着型空化为主, 同时兼顾云状空泡、空蚀、涡空化等,梳理了其研究中存在的几个关键科学问题,包括空化演变、空化流动的三维结构、失稳机制、空化不稳定性及其与低频压力脉动的联系、空化与旋涡的相互作用、空化与弹性水翼的流固耦合、空化对尾流场影响等.最后展望了空化水动力学的研究方向和未来发展趋势. 

Research progresses and prospects of unsteady hydrodynamics characteristics for cavitation

Cavitation is an important kind of complex multiphase flow with strong three-dimensional characteristic and high unsteadiness, which frequently occurred in a wide range of fluid machinery, marine propulsor, and hydraulic engineering and can generate the destructive behavior. Cavitation has been one of the most difficult and key problems in the area of hydrodynamics for quite a long time. In this paper, the research progress of unsteady hydrodynamics characteristics for cavitation is reviewed from the viewpoints of experimental and numerical investigations, respectively. And the existing problems in the cavitation research are also discussed. For the experimental study, the progress of the cavitation mechanism tunnel, measurement technology for cavitating flow and simultaneous sampling technique are introduced. For the numerical investigations, some of the most popular cavitation models and turbulence models are introduced by categorization, and the applications of large eddy simulation (LES) approach and validation & verification in cavitation simulations are discussed in detail. Then, mainly based on attached cavity but also other kinds of cavitation, such as cavitation cloud, cavitation erosion, and vortex cavitation, several basic but important problems are discussed. Problems discussed herein includes the evolution of attached cavity, the three dimensional structures of cavitation, the shedding mechanism of attached cavity, the unsteadiness mechanism of cavitation and its connection with the pressure fluctuations, the interaction between cavitation and vortex, the fluid-structure interaction in the cavitating flow around a flexible hydrofoil, influence of cavitation on the wake flow, and so on. Finally, prospects of the direction and trends of cavitation hydrodynamics research are discussed.