Flow compartmentalization and trailing-edge vortex suppression over hydrofoil with bio-inspired leading-edge protuberances

This study investigates the physical mechanism by which bio-inspired sinusoidal leading-edge protuberances induce flow compartmentalization and suppress coherent trailing-edge vortex formation in hydrofoil flow. Experiments were conducted in a cavitation tunnel using two-dimensional hydrofoils, including a baseline NACA 0012 and an L-E modified counterpart incorporating sinusoidal leading-edge tubercles. Particle image velocimetry (PIV), high-speed flow visualization, and laser Doppler velocimetry (LDV) were employed to characterize both cavitating and non-cavitating conditions. Under non-cavitating conditions, the baseline hydrofoil exhibits a distinct coherent trailing-edge vortex associated with strong shear-layer roll-up and wake unsteadiness. In contrast, the L-E modified hydrofoil shows a substantially weakened or absent dominant trailing-edge vortex. Vorticity and in-plane turbulent kinetic energy (TKE ip ) analyses further show that the LE-modified hydrofoil reduces the maximum normalized vorticity and (TKE ip / U ∞ 2 ) within the trailing-edge region by 84.2% and 71.3%, respectively, confirming substantial weakening of the concentrated rotational and fluctuation energy cores. A combined PIV–LDV analysis near the leading edge, supported by Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) reconstruction, reveals that the sinusoidal leading edge generates localized streamwise acceleration behind the trough regions, accompanied by wall-normal deflection, spanwise momentum redistribution, and a trough-centered counter-rotating vortex pair. These coupled motions reorganize the near-wall flow into compartmentalized three-dimensional structures, weaken the spanwise coherence of the developing boundary layer and shear layer, and thereby suppress coherent trailing-edge vortex formation. Under cavitating conditions, the same mechanism confines vapor structures primarily to the trough regions, inhibits spanwise cavity merging, and fragments large-scale cloud shedding into smaller localized cavities. The results show that sinusoidal leading-edge protuberances suppress coherent trailing-edge structures and promote cavitation compartmentalization through early three-dimensional momentum redistribution.