Fluid-structure interaction simulation of slam-induced bending in large high-speed wave-piercing catamarans

A ship in waves may experience a water impact event known as a slam. In this paper, slam-induced bending of wave-piercing catamarans in head seas is predicted by way of fluid-structure interaction simulations. The flow field during slamming of a wave-piercing catamaran is highly non-linear and cannot be accurately captured using potential flow methods as a result of the interactions between the flow fields produced by water entry of the separate demihulls and centre bow. Thus, the Reynolds-Averaged Navier-Stokes (RANS) equations are solved for rigid body motion of a vessel at model-scale. Verification and validation is conducted using model-scale data from a Hydroelastic Segmented Model (HSM). One-way and two-way interactions are computed considering vibration of the hull girder. In the case of one-way interactions, the computed fluid loads affect the structure, but the structural response does not affect the fluid domain solution whereas for the two-way interactions the structural response affects the fluid solution. A new method for capturing the non-linear time variation in added mass is developed and deemed necessary when computing one-way interactions, primarily as a result of the large changes in forward wetted area present for a wave-piercing catamaran. It is shown that two-way interaction simulation is not needed for predicting the slam induced hull girder loads. One-way interaction simulation can therefore be used allowing reduced computational effort.