Validation of dynamic cavitation model for unsteady cavitating flow on NACA66

Abstract

Unsteady cavitating flow is extremely complicated and brings more serious damages and unignorable problems compared with steady cavitating flow. CFD has become a practical way to model cavitation; however, the popularly used full cavitation model cannot reflect the pressure-change that the bubble experiences during its life path in the highly unsteady flow like cloud cavitating. Thus a dynamic cavitation model (DCM) is proposed and it has been considered to have not only the first-order pressure effects but also zero-order effect and can provide greater insight into the physical process of bubble producing, developing and collapsing compared to the traditional cavitation model. DCM has already been validated for steady cavitating flow, and the results were reported. Furthermore, DCM is designed and supposed to be more accurate and efficient in modeling unsteady cavitating flow, which is also the purpose of this paper. The basic characteristic of the unsteady cavitating flow, such as the vapor volume fraction distribution and the evolution of pressure amplitude and frequency at different locations of the hydrofoil, are carefully studied to validate DCM. It is found that not only these characteristics mentioned above accord well with the experimental results, but also some detailed transient flow information is depicted, including the re-entrant jet flow that caused the shedding of the cavity, and the phenomenon of two-peak pressure fluctuation in the vicinity of the cavity closure in a cycle. The numerical results validate the capability of DCM for the application of modeling the complicated unsteady cavitating flow.