Multiscale flow structure prediction in unsteady cavitating flow around the hydrofoil

Considering that large eddy simulation (LES) often requires more computational resources to capture small-scale flow characteristics, while the Reynolds-Averaged Navier-Stokes (RANS) methods offers better computational efficiency at the expense of accuracy. The traditional Zwart-Gerber-Belamri cavitation model (Z-G-B) has good universality but insufficiently considers the influencing factors of cavitation. This article proposes a method combining very large eddy simulation (VLES) with the Z-G-B cavitation model (VLES_Z-G-B). However, there remains a certain discrepancies between the predictions and experimental results. To address this, on the basis of the Z-G-B cavitation model, the unsteady cavitation computation method (VLES_Water_Non) is developed, considering the weak compressibility effect of the fluid and incorporating three components: the liquid, vapor, and non-condensable gas. The results indicate that the VLES_Water_Non method compensates for the deficiencies of the VLES_Z-G-B approach, and clarifying that the combined effect of re-entrant flow, side-incident reverse flow, and mainstream are the primary causes of cavity shedding. Using a robust Omega-criterion, multiscale flow features during the cavity evolution process were identified. Additionally, it was found that the vortex stretching and dilation terms are the main reason for the flow separation and formation of complex structures around the hydrofoil. The baroclinic torque term has an significant impact on the generation of vorticity during the shedding process of the cavity. This study is expected to provide a more precise scale resolution method and predictive accuracy for analyzing the internal flow mechanisms of complex fluid machinery.