Investigation of Hydrodynamic Behaviour of Wind Turbine GBS During Offshore Installation and Engineering Design Outcomes

Gravity Based Structure (GBS) is one of the main structural foundation concept planned to be used to accommodate offshore wind turbines in shallow water depth areas. Large scale deployment of such massive foundations raises technical issues regarding transport and installation of the GBS. This paper aims at presenting major outcomes of hydrodynamic analyses carried out to assess dynamic behaviour of the GBS during offshore installation. This study focuses on the last critical step of the installation process when the foundation is almost completely ballasted and close to the seabed grading layer. CFD analyses are conducted with OpenFOAM to estimate viscous damping of the GBS and to investigate the impact of seabed proximity and bedding layer porosity on hydrodynamic parameters. Based on damping coefficients derived from CFD, motion analyses are performed with Diodore™ to assess dynamic behaviour of the GBS in irregular waves. Results are benchmarked against responses obtained from different damping parameters and computation methods. This study allows providing some recommendations regarding hydrodynamics design methodology for this type of GBS installation analysis.