Cavitation erosion characteristics influenced by a microstructure at different scales

Abstract

The scale effect of vortex generators, as microstructures, influences cavitation erosion remains unclear, posing a key challenge to applying vortex generators in large-scale hydraulic machinery. In this study, the vortex generators (VGs) with heights of 0.25 mm (micro-VG) and 2.5 mm (large-VG), installed at the leading edge of a smooth NACA0015 hydrofoil, were investigated through experimental and simulation methods. The results demonstrate that the vortex generators can induce tubular vortexes that enhance near-wall flow stability. After installing the VGs, the large-scale cloud cavitation is effectively controlled. On the hydrofoil with micro-VGs, this control manifests as localized, small-scale cavitation shedding and collapse, while on the hydrofoil with large-VGs, the cavitation shedding is entirely absent, which shows that larger VGs further mitigate cavitation effects. Pressure signal analysis reveals that the VGs alter the pressure fluctuation period and reduce the main frequency amplitude compared to that on the smooth hydrofoil, with larger VGs providing superior suppression of pressure fluctuations. Additionally, an improved strength function method is proposed and applied, highlighting that the reduction in large-scale cloud cavitation by the VGs contributes to decreased erosion risk on the hydrofoil, with larger VGs showing enhanced effectiveness in preventing cavitation erosion.