Diagnosis of hub vortex–cavitation interaction faults in a waterjet propulsion pump via pressure signal processing: An experimental and numerical study

The waterjet propulsion pump is essential for high-performance marine vessels, yet hub vortex at the guide cone tip induces cavitation and flow instabilities. This study investigates hub vortex–cavitation interaction faults via experiments and numerical simulations. Pressure measurements at the guide cone tip are conducted at 300–1000 r/min. Signals are processed using adaptive FIR filtering, power spectral density (PSD) analysis, continuous wavelet transform, and statistical methods. Detached Eddy Simulation with the Zwart-Gerber-Belamri cavitation model provides flow field validation. Results show pressure fluctuations are dominated by broadband turbulence, with vortex characteristic frequency stable at 5.1–5.5Hz. Within the hydrodynamic key band, PSD decay exponent increases from about −1.86 at 300 r/min to −2.67 at 1000 r/min. At 1000 r/min, the exponent nearly coincides with the theoretical −8/3 value, suggesting cavitation bubble collapse may act as micro-scale “shock events” in the pressure spectrum. High-frequency energy (>100Hz) increases from 3.0% to 6.4% (CWT analysis), indicating intensified cavitation. Skewness transitions from negative at 300–500 r/min to positive at 1000 r/min, marking cavitation-dominated fault onset. These features—power-law decay exponent, high-frequency energy proportion, and skewness transition—are effective indicators for cavitation intensity and fault severity. These findings provide a basis for condition monitoring of waterjet propulsion pumps.