Research on multiscale cavitation characteristics of hydrofoils based on an Eulerian–Lagrangian bidirectional coupling model

During the operation of marine fluid machinery, surface cavitation on its power components induces complex multiscale phase transitions and vortex interactions. Conventional Eulerian frameworks, such as the Volume of Fluid (VOF) method, often fail to precisely resolve sub–grid microbubble dynamics and their momentum feedback, leading to physical inconsistencies in predicting cavity shedding. To address this, an enhanced Eulerian–Lagrangian bidirectional coupling model is proposed to quantify the multiscale vortex transport characteristics of a cavitating twisted hydrofoil. This framework incorporates subgrid–scale turbulent kinetic energy into the Rayleigh–Plesset equation and implements a rigorous conversion criterion that ensures strict mass and momentum flux conservation between the phases. By retaining discrete sub–grid bubble clusters during cavity collapse, the Eulerian–Lagrangian model predicted an approximately 10% larger total vapor volume than the conventional Eulerian model. Furthermore, vorticity transport analysis reveals that explicit resolution of sharp density gradients at the phase interface accurately captures the local amplification of baroclinic torque. Baroclinic torque emerges as a dominant local source of interfacial vorticity during re–entrant–jet initiation and “U”–shaped cavity shedding. The findings elucidate the governing mechanism of phase–change–induced anisotropic vortex transport; this study provides a framework for high–precision numerical simulations of cavitation in marine fluid machinery.