Water entry of a projectile impacting the floating structure with an optimised computational fluid dynamics-discrete element: Fluid-solid interaction and multi-scale fracture dynamics

The interaction between marine floating structures and projectiles during water entry plays a crucial role in understanding fluid-structure interactions in polar and offshore environments. This study investigates the impact dynamics of a projectile on a floating structure, emphasising the fluid-structure coupling effects, including the impact-induced cavity evolution, stress wave propagation and fragmentation processes. The computational approach integrates fluid dynamics and discrete element methods (CFD-DEM), allowing for detailed simulation of multi-phase interactions during projectile impact. To address the disparity between fluid grid resolution and particle scale, a dual-grid strategy is incorporated, enabling accurate resolution of multi-scale interactions. The results highlight the fundamental mechanisms of impact water entry, where stress waves radiate through the structure, causing local damage and initiating the formation of fragments. These fragments, in turn, influence the stability of the cavity interface and modify the impact dynamics. The interplay between the floating structure's buoyant support and the surrounding water contributes to complex load variations on the projectile. Ultimately, the study provides insights into the multi-scale fracture mechanisms induced by projectile impact, with potential applications in improving the design and resilience of structures in dynamic marine environments.