Numerical modelling of a vertical cylinder with dynamic response in steep and breaking waves using smoothed particle hydrodynamics

Highly nonlinear near-breaking and spilling breaking wave groups are common extreme events in the ocean. Accurate force prediction on offshore and ocean structures in these extreme wave conditions based on numerical approaches remains a problem of great practical importance. Most previous numerical studies have concentrated on non-breaking wave forces on rigid structures. Taking advantage of the smoothed particle hydrodynamics (SPH) method, this paper addresses this problem and presents the development and validation of a numerical model for highly nonlinear hydrodynamics of near-breaking and spilling breaking waves interacting with a vertical cylindrical structure using the SPH-based DualSPHysics solver. Open boundaries are applied for the generation of extreme wave conditions. The free-surface elevation and flow kinematics precomputed within another numerical model are used as boundary conditions at the inlet of a smaller 3-D SPH-based numerical model to replicate the near-breaking and spilling breaking waves generated in a physical wave flume. A damping zone used for wave absorption is arranged at the end of the domain before the outlet. Numerical results are validated against experimental measurements of surface elevation and horizontal force on the vertical cylinder, demonstrating an agreement. After validation using a fixed model for the cylinder, a dynamic model is used to study the response to extreme wave events. Numerical results have also shown that the spilling breaking wave forces are significantly larger compared with near-breaking wave forces, and the secondary load cycle phenomenon becomes larger with dynamic response included in the present study.