Cavitation erosion risk on a hydrofoil using a multi-scale method

The present study employs a two-way coupled multi-scale method to simulate and analyze the cloud cavitation flow around a hydrofoil, based on which the distribution of cavitation erosion risk on the hydrofoil is evaluated. The numerical results demonstrate that the multi-scale method can capture not only the overall evolution characteristics of cloud cavitation but also the generation, growth, and collapse of small-scale bubbles. Throughout the majority of a cavitation cycle, the scale of the Lagrange bubbles roughly follows a logarithmic Gaussian distribution. However, it shows a double-peak characteristic as a result of bubble production from both the sheet cavity and the shedding cloud. The distribution of local erosion risk, which is closely aligned with experimental findings, is assessed based on the collapse of small-scale bubbles. The erosion risk is greatest near the closure line of the sheet cavity, which is due not only to the collapse of bubbles around the shedding cloud but also to the shedding and breakdown of small-scale vapor structures during the development of the reentrant jet. During the cavitation cycle, the erosion risk is highest when the shedding cloud forms and the erosion risk decreases as it moves downstream. The multi-scale numerical analysis reveals that the cavitation number alone is insufficient for characterizing cavitation and its erosive effects. For a given cavitation number, the mean diameter of Lagrange bubbles increases with the inflow velocity. Furthermore, the total impact energy from bubble collapse on a hydrofoil follows a power-law dependence on the inflow velocity.