In this study, the breaking wave forces on a jacket (steel space frame) structure are simulated using a 3D numerical model. The model is based on solving the viscous and incompressible Navier-Stokes equations for a two-phase flow (air and water) model and the volume of fluid method (VOF) for treating the free surface of the water. A cut-cell method is used to install the complicated geometry (e.g., jacket structure) in the computational domain. The numerical model is validated by using experimental data obtained at the Large Wave Channel (GWK), Hannover, Germany. Free surface elevation, water particle velocities and total forces on the structure were calculated with the numerical model, for both breaking and non-breaking cases and are compared with the experimental data. The simulation results show good agreement with the experimental data. Based on the validated numerical results, slamming coefficients on the front and back vertical members are estimated. In addition to this, the reasons why maximum values of breaking wave forces measured in the total time series show a large degree of scatter are briefly discussed.
The substructures for wind turbines are usually monopiles, jacket structures, tripods or gravity based structures. Many of the existing wind farms are built with monopile substructures due to the simplicity in the design and installation. However, in comparison with the monopile, the jacket structure can accommodate larger wind turbine capacity and can operate in deeper waters. The current trend in the wind turbine industry is towards jacket type foundations due to the unique advantages of jacket structures over monopiles.
Jacket structures (truss type foundations) installed in shallow water regions are subjected to highly varying hydrodynamic forces. The forces from breaking waves, especially plunging breaking waves are a major concern in the design of such structures as they are often located on shoals where wave breaking occurs. These breaking wave forces are in addition to the Morison forces acting on the structure (Eq. 1). The wave slamming force acting on cylindrical piles can be written as (Eq. 2, Goda et al., 1966).