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.