Numerical investigation of condensation shock and re-entrant jet dynamics around a cavitating hydrofoil using a dynamic cubic nonlinear subgrid-scale model

Cavity shedding mechanisms, such as those due to re-entrant jets (RJ) and condensation shocks (CS), are important but challenging topics in cavitating flows. This study investigates unsteady cavity shedding around a NACA66 hydrofoil using a self-defined compressible cavitation solver based on OpenFOAM with a dynamic cubic nonlinear subgrid-scale model. The predictions give satisfactory agreement with experimental data for the quantitative pressure evolution and the cavity shedding behavior induced by the re-entrant jet and the pressure wave. Moreover, the numerical data provides deeper insight into the pressure wave characteristics (e.g. propagation speed, wave intensity, shock Mach number, etc.) during cavity contraction. Multi-perspective analyses demonstrate that the pressure wave is a condensation shock which is responsible for the attached cavity abruptly disappearing. Additionally, the different influences of the re-entrant jet and the condensation shock on the local flow patterns are compared in detail in terms of the duration, average motion velocity, cavity behavior, formation mechanism and pressure intensity. The results show the condensation shock is characterized by fast propagation speed, short duration and high pressure pulse, which differs from the re-entrant jet features. This research provides an improved understanding of the cavity shedding mechanism around a cavitating hydrofoil and demonstrates the effectiveness of the current compressible cavitation solver.