Numerical study on passive control of water-exit cavitation and impact loads via porous media

Abstract

Cavity collapse during underwater vehicle water exit induces severe transient impact loads that threaten structural integrity, while the passive control of this process via porous media remains largely unexplored. This study employs a Reynolds-averaged Navier–Stokes and volume of fluid framework coupled with a volume-averaged porous-media model to investigate the effect of porous cladding on cavitating flow and collapse loads during the constant-velocity water exit of an underwater vehicle under both vertical and angled conditions, covering a Darcy number (Da) range from 1.0 × 10−6 to 1.0 × 10−3. The results demonstrate that the porous cladding substantially mitigates the collapse severity relative to the solid case, reducing the maximum transient impact pressure peak by up to 65.20% and decreasing the overall peak cavity volume by up to 44.21%. As permeability rises, the external reentrant jet becomes less distinct, and cavitation penetrates deeper into the porous media. Meanwhile, the permeable wall allows part of the collapse-induced flow to penetrate into the porous media, where Darcy–Forchheimer resistance spreads the near-wall flow response and promotes viscous and inertial dissipation, collectively reducing the overall collapse load.