Cavitation Dynamics and Vorticity Analysis of a Clark‐Y Hydrofoil and a Venturi Geometry Based on the DCM

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Literature research has shown that the high turbulent viscosity of original Reynolds‐averaged Navier–Stokes (RANS) models in the wake reduces the cavitation instability, resulting in an unreasonable performance prediction of the cavity generation, shedding, and collapse. Hence, a density‐corrected model (DCM) is utilized to improve the prediction capacity of the RNG k–ε model in the two‐phase flow simulation. Selected results are provided for two cases, namely, a two‐dimensional Clark‐Y hydrofoil and a Venturi geometry associated with the unsteady cavitating flows. We compare hydrodynamic coefficients, cavity characteristics, and time‐averaged velocity with available experimental results. This work is aimed at providing a better physical insight to describe the vortex dynamics and structures during the cavity evolution, explaining the mechanism of the transient cavitating flows by quantifying the force coefficients of the cavity and its surrounding turbulent structures, and revealing the promoting effect of the re‐entrant jet on the cavitation transition. In addition, vorticity transport equations are conducted to analyze the interaction of vortex and cavitation. The results demonstrate that the DCM has sufficient robustness to predict the periodic cavity evolution of generation, breakup, shedding, and collapse. An unsteady cavitation process contains the development of complex vortex structures. Re‐entrant jet near trailing of the attached cavity leads to distinct changes of velocity gradient, which has great influence on production and dissipation of vorticity. Intensive mass transfer between liquid and vapor phases may introduce the volume expansion or contraction as well as the baroclinic torque, which leads to unsteady distribution of vorticity.