Experimental investigation of combined active-passive control on cavitating flow around a three-dimensional hydrofoil

Motivated by realistic operating conditions, a three-dimensional NACA0015 hydrofoil was investigated for cavitation control using vortex generators and air injection. To the authors’ knowledge, this is the first study to simultaneously compare cavitation control using vortex generators assisted with multiple air-injection rates. To assess the effectiveness of cavitation control, three configurations were examined: a plain hydrofoil, a hydrofoil equipped only with a vortex generator, and a hydrofoil furnished with vortex generators combined with air injection. Experiments were conducted at a Reynolds number of 5.5 × 10 5 and an angle of attack of 12°, covering cavitation numbers from 3.7 (inception) to 1.8 (cloud cavitation), with air supplied between 1 and 3 liters per min (L/min). The analysis relied on synchronized force measurements and high-speed imaging, combined with proper orthogonal decomposition, dynamic mode decomposition, fast Fourier transform, and wavelet analysis. At σ = 1.8, the combined vortex-generator and air-injection strategy operated at 2 L/min reduced the time-averaged cloud-cavity length by about 87% compared to the plain hydrofoil and by about 85% relative to the vortex-generator-only configuration. The vortex-generator-only configuration was effective mainly in the sheet and partial cavitation regimes, whereas the combined vortex-generator and air-injection configuration was more robust in suppressing cavitation activity and further shortened the cavity length.