Multi-Scale Two-Phase Flow Modeling of Sheet and Cloud Cavitation

A multi-scale two-phase flow model based on an Eulerian/Lagrangian coupled approach is developed to capture the sheet cavitation formation and unsteady breakup and cloud shedding on a hydrofoil. No assumptions are needed on mass transfer. Instead, natural free field nuclei and solid boundary nucleation are modelled and enable capture of the dynamics. The multi-scale model includes a micro-scale model for tracking the bubbles, a macro-scale model for describing large cavity dynamics and a transition scheme to bridge the micro and macro scales. With this multi-scale model small nuclei are seen to grow into large bubbles, which eventually merge to form a large scale sheet cavity. A reentrant jet forms under the sheet cavity, travels upstream, and breaks the cavity, resulting in high pressure peaks as the broken pockets shrink and collapse while travelling downstream. The results for a 2D NACA0015 foil are in good agreement with published experimental measurements in terms of sheet cavity lengths and shedding frequencies. Sensitivity assessment of the model parameters and importance of 3D effects on the predicted major cavity dynamics are also discussed in details.