Passive cavitation mitigation on hydrofoils via porous media: A comparative study of LES and RANS models

Abstract

This study numerically investigates the use of porous media as a passive strategy for mitigating cavitation on a NACA 66 (MOD) hydrofoil subjected to unsteady two-phase flow. Employing the Volume of Fluid (VOF) method alongside the Schnerr–Sauer cavitation model, simulations are performed at two cavitation numbers (σ = 1 and 0.7) for both 2D and 3D geometries. The porous region, characterized by a porosity of 0.95. and spanning one-third of the suction side, is represented as a momentum sink using Ergun's equation in ANSYS Fluent. Three turbulence models are utilized in the 2D simulations: Large Eddy Simulation (LES), realizable k–ε, and k–ω SST turbulence models to evaluate their predictive performance. For the 3D simulations, the LES turbulence model is employed to capture three-dimensional flow and validate the effectiveness of the porous media. The treatment of the porous surface influences cavitation dynamics by stabilizing the boundary layer, minimizing sharp pressure gradients, and limiting the growth of cavitation bubbles. Contour visualizations of the pressure coefficient, velocity magnitude, and vapor volume fraction indicate that the porous layer reduces negative pressure near the wall, lowering local suction intensity and delaying cavitation inception. As a result, the formation of re-entrant jets and aggressive cavity shedding, which are dominant in non-porous setups, is mitigated. Additionally, distributions of turbulent kinetic energy (TKE), z-vorticity, and baroclinic torque illustrate that the porous media diminishes vortex strength and wake instabilities. Spectral analyses of drag and lift coefficients through Fast Fourier Transform (FFT) reveal a notable reduction in high-frequency components for the porous case, demonstrating its ability to mitigate unsteady hydrodynamic loads. Among the tested configurations, a trailing-edge porous layer with a porosity of 0.95 provides the most balanced performance, offering the best compromise between hydrodynamic efficiency, cavitation suppression, and flow stability for practical operation. Collectively, these findings highlight the potential of porous integration as a robust and energy-efficient approach to enhance hydrofoil stability and cavitation resistance in marine systems.