Effects of inflow on initial cavitation and critical collapse state of a pump-jet propulsor in ice-blockage conditions

The ice blockage effect caused by brash ice entering the internal flow passage of a pump-jet propulsor (PJP) severely deteriorates its cavitation performance. To investigate the influence of inflow velocity on cavitation inception (cavitation number σ n = 3.0) and critical collapse ( σ n = 1.5) under ice blockage, this paper employs Improved Delayed Detached Eddy Simulation method with the Schnerr-Sauer cavitation model for advance coefficients J = 0.2∼1.0. Hydrodynamic performance, excitation forces, cavitation evolution, and vortex coupling are systematically analyzed. Results show that under σ n = 1.5, the optimal condition is J = 0.8, giving rotor thrust coefficient K Tr = 0.51039 and open-water efficiency η 0 = 0.58413. Low J (≤0.6) induces severe cavitation; at J = 0.2, cavitation volume is 3.23 times that at J = 0.8, and total thrust drops 34.45% compared to σ n = 3.0 and J = 0.2. Under cavitation inception, excitation force characteristics are opposite to ice-free conditions. At σ n = 3.0 and J = 0.2, the interquartile range of thrust fluctuation is 3.47 times, and duct excitation frequency-domain energy reaches 20.40 times that at σ n = 1.5. High-frequency generation and collapse of tiny bubbles are the core cause of excitation force increase. Ice-induced vortexes couple with tip and leakage vortexes, reconstructing the vortex structure; cavitation strength determines vortex integrity. This study fills the research gap on PJP inflow velocity and cavitation in polar regions.