Large-eddy simulation of bio-inspired leading-edge deformation for cavitation control on a hydrofoil

Inspired by the water-entry head morphology of cetaceans, this study investigates a biomimetic leading-edge deformation strategy for a symmetric NACA (National Advisory Committee for Aeronautics) 0009 hydrofoil (with chord length C = 100 mm). A series of deformation configurations was constructed by systematically varying the leading-edge deformation region (x₀) and nose-drop distance (d₀), and their cavitation control performance was evaluated in detail. High-fidelity large-eddy simulations were conducted to analyze the cavity structure, boundary layer characteristics, and hydrodynamic responses of each configuration. The results reveal that moderate leading-edge deformations (d₀ > 0.02C, x₀ = 0.2C-0.4C) significantly reduce cavity size, suppress unsteady cloud cavitation, and induce strong favorable pressure gradients near the cavity closure. These changes accelerate the boundary layer and enhance near-wall momentum transport, leading to a reduction in the resolved Reynolds shear stress. As the reentrant jet weakens and the cavity becomes more stable, vortex structures remain attached to the suction surface, resulting in a more stable and orderly flow field. Meanwhile, the lift-to-drag ratio increases substantially from 14.46 for the original hydrofoil to 45.67 under typical deformation parameters (x₀ = 0.3C, d₀ = 0.03C). When the deformation region is fixed at x₀ = 0.3C, increasing d₀ to 0.04C leads to the complete elimination of cavitation on the suction surface. This biomimetic approach offers new physical insights and practical design strategies for low-cavitation applications in marine propulsion and hydraulic machinery.