Particle-size-induced inertial modulation of cavitation and near-wall impacts in a sediment-laden Pelton bucket flow

Particle-laden cavitating wall flows involve coupled changes in particle inertia, pressure recovery, vapor topology, and near-wall impact concentration. Using a sediment-laden Pelton bucket flow as an application-motivated high-speed hydraulic configuration, this study examines how sediment particle size regulates the indirect hydrodynamic coupling between cavitation and particle-impact erosion. Unsteady gas–liquid–solid simulations were performed using the Volume of Fluid method, the Shear Stress Transport k–ω turbulence model, the Dense Discrete Phase Model, the Schnerr–Sauer cavitation model, and the Oka erosion model. Under fixed particle density, sediment concentration, fluid properties, and operating conditions, a dual-scale Stokes-number framework was used as a bounded interpretive tool: the reference Stokes number provides a common domain-scale indicator, whereas a region-averaged local Stokes number characterizes impact-related inertia in representative near-wall regions. From clear water to coarse sand, the selected-surface cavitation area fraction increased from 0.28% to 0.45%, the low-pressure area fraction increased from 0.38% to 0.85%, and outlet-edge cavitation coverage increased from 18.2% to 65.8%. Fine sand reached local Stokes numbers above unity, whereas coarse sand reached O (102), consistent with stronger liquid-film penetration and concentrated impacts. After removing the explicit Oka diameter multiplier, the diameter-normalized erosion indicator still increased from 2.42 × 10−6 to 6.72 × 10−6 kg m−2 s−1, while erosion coverage increased from 12.8% to 68.2%. The results show that the erosion response reflects both model-embedded diameter dependence and particle-size-induced redistribution of impact velocity, angle, frequency, and localization.