Numerical Water Impacts of 2D Hull Forms using Dynamic Overset Meshing

Abstract

The phenomenon of slamming is often the critical design load for high-performance marine craft. Slamming involves the solid-fluid impact of a hull structure, resulting in large forces acting on the structure from the large volume of water displaced in a very short time frame. Due to its importance in the design and operation of marine craft, the impact of ship forms into water has been the focus of a significant body of literature. These studies have primarily focused on rigid shapes, so the effects of hydroelasticity have not been examined in detail. This paper presents a robust and practical methodology for simulating water impacts involving overset meshing and the Volume of Fluid (VOF) method using the Ansys Fluent 2021 R1 Computational Fluid Dynamics (CFD) solver. The framework involves a high resolution dynamic overset mesh attached to the body in a coarse static Cartesian background mesh. Results for a simple 2D wedge impact are compared to experimental and analytical results and a good agreement to the validation material is observed. A 2D transverse section based on the IMOCA60 racing yacht Banque Populaire VIII is then analysed to obtain impact force and pressures. Results capture the peaked pressure distributions characteristic of slamming, with possible effects of air entrapment. The methodology presented is applicable for designers of high-performance sailing craft to improve the prediction of hydrodynamic loading on their hull-form designs. The overset method can quickly and easily be applied to a number of different geometries and impact events with minor changes between models.