Wave impact pressure and kinematics due to breaking wave impingement on a monopile

Abstract

Breaking wave impact on a vertical cylinder in shallow waters is investigated numerically with the two-phase flow computational fluid dynamics model REEF3D. The model is based on the incompressible Reynolds-Averaged Navier-Stokes (RANS) equations together with the level set method (LSM) and k−ω turbulence model. The spatial and time development of the maximum wave impact pressure and the associated velocity components are examined. Further, the breaking wave characteristics and geometric properties are evaluated with two-dimensional simulations. Comparisons of numerical results and experimental data indicate good agreement for free surface elevations and the characteristics at breaking and the breaking wave forces. A total of 9 two-dimensional and 27 three-dimensional simulations are performed to investigate the influence of the incident wave characteristics, wave impact conditions and breaker types on the maximum wave impact pressure and kinematics. The factors influencing the spatial and temporal variability of the vertical distribution for the maximum impact pressure and kinematics are investigated. Three impact conditions are considered in this study: (1) the wave with a vertical front breaks at the cylinder, (2) the broken wave hits the cylinder with a moderately developed overturning wave crest, and (3) the broken wave impacts the cylinder with a fully developed overturning wave crest. Further, the vertical and longitudinal variations of the maximum impact pressure during the breaking wave impact on the monopile are assessed. The numerically simulated free surface deformations during the wave impact are also presented and discussed. Finally, the total breaking wave force and the maximum impact pressure are analyzed for spilling and plunging breakers under different wave impact conditions.