Session: Hydrodynamic and Coupled Analyses-1

Paper Number: 164789

164789 - Breaking Wave-Induced Slamming Load From Underlying Linear Properties 

Abstract: 

The offshore wind industry is currently booming thanks to the falling production costs and the pressing need for energy transition. Greater efficiency is expected from harnessing the wind further offshore in deep waters using Floating Offshore Wind Turbines (FOWT). The structures can be subject to extreme waves inducing severe damages e.g. slamming loads from breaking waves. Hydrodynamic impact load depends on the relative kinematics between the body and the fluid which must be assessed during a slamming event occurring on a structural element. Fully coupled dynamic analyses of offshore structures are generally performed using linear wave theory and do not include wave breaking. This abstract discusses the modeling of the extreme breaking wave force on offshore wind turbines using only the underlying linear properties of the incoming wave, with a view to incorporating slamming load into coupled mid-fidelity models.

This work has been carried out during the DIMPACT project which proposes a methodology to derive breaking wave load on (floating) offshore wind turbines, addressing three main challenges: 

1)      The detection of breaking events and the estimation of the breaking severity from Airy wave theory

2)      Access to breaking wave properties to calculate slamming force

3)      Modeling a realistic non-breaking force from an equivalent nonlinear regular wave

Using fully nonlinear potential flow (FNPF) simulations, Hulin et al. (2024) established a linear equivalent criterion for wave breaking, as well as an estimate of the breaking wave severity using only the linear properties of the waves. In the linear-to-nonlinear transformations proposed by Prevosto & Filipot (2025), the wave celerity and crest height of the linear wave are corrected for the nonlinearities. Parametric models for breaking wave properties are derived from the database of FNPF waves. The breaking front, rear wave face and kinematics at the free surface are parameterized with the breaking severity. Those wave properties fed a slamming load formulation applied in a strip-theory approach (Renaud et al., 2023). This approach for deriving the slamming load induced by a breaking wave is validated by force measurements (Hulin et al., 2025) for several configurations of interest, including the effect of cylinder orientation and dynamics. The method is implemented in the mid-fidelity model OpenFAST. The nonbreaking wave load should also be accurately described to get the total force acting on the structure. The force computed from the classical Morison equation using linear wave kinematics does not provide an accurate estimate of the nonbreaking wave load.  Thus, nonlinear kinematics is derived from an equivalent steady surface gravity wave (Clamond & Dutykh, 2018). The force is then computed from a nonlinear Morison-type formulation accounting for variable hydrodynamic coefficients depending on the immersion depth in the fluid (Renaud et al.,2023). The resulting total forces are compared with the experimental data to validate the methodology.

Presenting Author: Paul Renaud France Energies Marines

Presenting Author Biography: R&D Engineer at France Energies Marines, specializing in the study of extreme events such as breaking waves and tropical cyclones. My work focuses on understanding and mitigating the impacts of these phenomena to enhance the resilience and sustainability of offhsore wind turbines.

Authors:

Paul Renaud France Energies Marines
Florian Hulin Ecole Centrale de Nantes
Alice Courtet France Energies Marines
Alan Tassin IFREMER RDT
Marc Prevosto France Energies Marines
Jean-François Filipot France Energies Marines
Nicolas Jacques ENSTA Bretagne UMR CNRS 6027, IRDL
Neil Luxcey France Energies Marines