ENHANCEMENTS OF COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF AIR ENTRAPMENT AND FLUID-STRUCTURE INTERACTION DURING PLATE ENTRY TO WATER THROUGH VOF-SLIP AND ADAPTIVE DISCRETIZATION SCHEMES

A Computational Fluid Dynamics (CFD) analysis of air entrapment and structural response during flat plate entry to water is presented. Slamming loads remain of concern for the design of safe and efficient ships and offshore structures to ensure structural integrity during extreme. Besides ships with large bow flare or horizontal stern planes, slamming events also occur for fast small craft with stepped hulls. Ditching of airplanes and vehicle wading represent non-marine applications. The advance of computational methods in engineering has enabled fluid-structure interaction (FSI) simulations for slamming. A crucial task of solving the coupled fluid and structural problem is the accurate resolution of free surface dynamics and phase interactions between water and air. Numerical ventilation on the bottom plating can arise due to discretization issues and curtail the resolution of physical aeration effects. The study at hand was based on a Finite-Volume (FV) method and the numerical solution of Reynolds-averaged Navier-Stokes (RANS) equations. Emphasis was laid on numerical techniques to contain numerical ventilation whilst limiting the increase in computational cost. In doing so, adaptive discretization schemes were employed. Namely, model-based adaptive mesh refinement (AMR) and time stepping for both motions of bodies (rigid and elastic) and the free surface. Additionally, the underlying Volume of Fluid (VoF) method was enhanced through consideration of slip between water and air to improve air entrapment predictions. Comparison was drawn to a novel experimental analysis for which both structural responses and high-resolution imagery of aeration were available. It was demonstrated that above enhancements not only lead to better capturing of air entrapment and reduced numerical ventilation, but also offered more flexible modeling concepts and potential performance gains.