Hydrodynamic Impact of Cavitating Jets on Marine-Coated Steel Surfaces: Parametric Analysis and Non-Destructive Cleaning Performance

Biofouling on ship hulls increases hydrodynamic drag, fuel consumption, and lifecycle maintenance costs. This work presents a quantitative experimental investigation of normal impact forces generated by cavitating and conventional high-pressure water jets on marine-coated carbon-steel surfaces. Analytical calculations and computational fluid dynamics (CFD) simulations were performed to evaluate internal flow and cavitation dynamics. Normal forces were measured using a calibrated load cell as a function of stand-off distance ([0,01 − 0,35] m) and jet incidence angle ([0,349–1,57] rad) under submerged conditions. The cavitating jet was generated by an in-house developed Venturi-type stainless-steel nozzle costing under €40. Results show that the cavitating jet delivered a quasi-stable normal force of 4.5 ± 0.2 N over [0,01–0,04] m, decaying by only 22% at 0,35 m (3.5 N), whereas the conventional jet force decayed rapidly. Surface characterization combining profilometry and dry-film-thickness monitoring confirmed a cleaning efficiency of 72 ± 6% at the optimal window ( d = [0,02–0,04] m, θ = [0,524– 0.786] rad) with no measurable coating degradation. These results demonstrate the suitability of low-cost cavitating jets for coating-safe underwater maintenance and provide operational guidelines directly applicable to autonomous marine cleaning systems.