Effect of cavitation structures and flow rates on pressure pulsation in the inducer: An experimental investigation

The generation of noise and structural vibrations in inducers caused by unsteady cavitation represents a critical technical challenge, necessitating comprehensive investigation into the dynamic characteristics of cavitation-induced pressure pulsations. The method of wavelet decomposition and spectral proper orthogonal decomposition (SPOD) were employed to analyze the connection between instantaneous pressure pulsations and the cavitation structures. The results indicate that hub cavitation and back-flow vortex cavitation occur at 0.6-0.8 ϕ_d, where ϕ_d is defined as the flowrate coefficient for which the inducer has been designed. Perpendicular vortex cavitation focuses on 0.8-1.0 ϕ_d and interacts with the sheet cavitation on the adjacent suction surface. Eddy-cavitation appears at 1.0-1.2 ϕ_d. However, the tip leakage vortex cavitation area shrinks from a small flow rate to a large one. Cavitation growth primarily induces low-frequency pressure pulsations about 147.5 Hz; cavitation shedding and collapsing at 0.6-0.9 ϕ_d induces high-frequency pressure pulsations above 636 Hz, whereas 1.0-1.2 ϕ_d induces low-frequency pressure pulsations below 322 Hz. SPOD analysis of inducer cavitation structures demonstrated decreasing modal spatial sizes with elevated decomposition frequencies and mode orders at constant flow rates, while increased flow rates reduced modal spatial dimensions with constant spectral parameters. The cavitation development process induced a pressure coefficient that increased from valley-to-peak. However, the shedding cavitation migration process generated peak-to-valley pressure transitions.