Numerical investigation of cloud-cavitation control over a Clark-Y hydrofoil using Salvinia -morphology-inspired branched microstructures

Periodic cloud-cavity shedding causes severe load fluctuations and pressure pulsations, thereby degrading hydrodynamic performance. Branched solid microstructures inspired by the geometry of Salvinia trichomes were introduced onto the suction side of a Clark-Y hydrofoil for passive control. Large-eddy simulations examined their effects on cloud-cavitation evolution, hydrodynamic performance, and vortex–cavitation coupling. Among the three S = 1.0 mm placement cases, the near-trailing-edge configuration (CS3) delivered the most favorable balance of hydrodynamic performance and cavitation suppression. Relative to the unmodified hydrofoil (Clean), CS3 increased the mean lift coefficient by 4.04% and reduced the mean drag coefficient by 4.96%. It also improved the mean lift-to-drag ratio by 9.47% and reduced the mean vapor volume by 52.36%. For geometric comparison, cylindrical-post (CP) and hemispherical-bump (HB) arrays were evaluated in the same downstream region under identical flow and numerical conditions with explicitly documented geometric constraints. Relative to Clean, HB and CP reduced the mean vapor volume by 56.60% and 26.41%, while changing the mean lift-to-drag ratio by +3.08% and −1.18%, respectively. Analyses of near-wall re-entrant-flow velocity and the magnitude of suction-side pressure recovery characterized the hydrodynamic response of CS3 relative to conventional protrusions. Further analyses of velocity vectors, local vapor volume fraction, Q-criterion vortical structures, and vorticity-transport terms clarified the associated vortex–cavitation interactions. Refined-time step Clean, paired-spacing (CS2-S1.2 and CS3-S1.2), and doubled-span Clean and CS3 simulations assessed time step, array-density, and spanwise-domain sensitivity. These findings provide a geometry-based biomimetic approach for controlling cloud cavitation and improving hydrofoil performance.