Split-type vortex generator design and structure optimization for hydrodynamic performance and cavitating flow stability

To address the intense flow fluctuations during the transition from sheet cavitation to cloud cavitation over hydrofoils, a split-type vortex generator (SVG) based on the slit-induced self-excitation principle is proposed. The effects of structural parameters and end-face modifications on cavitation control performance are systematically investigated. Parametric analysis indicates that an SVG spacing of 0.7 mm yields the most effective cavitation suppression, significantly reducing low-frequency cavitation-induced fluctuations, effectively damping oscillations in lift and drag coefficients and improving lift-to-drag ratio. To further mitigate flow disturbances near the SVG tip region, three endface modification strategies are introduced: normal-direction design (SVG1), spanwise-direction design (SVG2), and combined strategy (SVG3). SVG1 effectively prolongs the sheet cavitation phase, while SVG2 provides superior control over mid-to-high frequency pressure oscillations and noise suppression. SVG3 integrates the strengths of both approaches and achieves balanced performance in pressure fluctuation reduction, hydrodynamic performance, and noise control. With the optimized SVG configuration, the amplitude of the dominant pressure fluctuation frequency is reduced by up to 32.43%. The noise control capabilities of the SVG structures are further evaluated, confirming the effectiveness across multiple frequency bands. The optimized SVG configuration demonstrates strong noise reduction, with a maximum decrease of 12.09 dB at the monitoring point. Overall, the SVG demonstrates excellent cavitation control capability during the sheet-to-cloud cavitation transition, enhancing the coherence of cavity shedding in the cloud cavitation stage. By delaying the transition and suppressing disturbances induced by stagnation vortices, the SVG improves the cavitating flow stability and hydrodynamic performance.