The offshore wind industry is following a fast increase in Europe, leading developers to consider sites with higher water depths and to move to floating foundations. Floating Offshore Wind Turbines (FOWT) are complex systems whom design requires multi-physic models: aerodynamics, structural dynamics, hydrodynamics. The present paper investigates the validation of 2 FOWT numerical models against a set of experimental results provided by the University of Plymouth, within the ISOPE 2023 FOWT comparative study. The first numerical model, DIEGO, is an aero-hydro-servo-elastic solver similar to engineering tools used by the industry for the FOWT structural design. It can be seen a "low-fidelity" model, as it relies on simplified hydrodynamic assumptions (linear potential flow, Morison drag). The second numerical model, neptune_cfd, is a multi-phase Navier-Stokes solver able to handle wave-body interactions using a discrete forcing method to represent the structure on a cartesian mesh. It can be seen as a "high-fidelity" model of the FOWT in waves. The results presented show a good agreement between the 2 numerical models and the experimental references.


To limit the effect of climate change, the decarbonization of the electricity production must be supported by a fast development of renewable energies. Among them, solar and wind have the largest technical potential and their level of readiness make them very good candidates to contribute to the reduction of heat gas in the next decades. After 30 years of development offshore, with about 30 GW installed in the European shallow waters, the wind energy is now harvesting the high potential of deep waters in many countries with demonstrators installed in Europe, Japan, US or China. Despite announcements of commercial scale tenders in France, Norway and the US, the floating wind industry is still at the beginning of its learning curve and has many challenges to address. One of them is the structural design of floating wind turbines, which involve several physics like aerodynamics and hydrodynamics. A key issue is the estimation of the floater motions, affecting both the turbine behavior and the stresses in the system. Numerical models are used in the engineering phase of floating wind projects to capture the motions due to waves and wind, based on the state-of-the-art aeroelastic methods coming from the onshore wind industry and wave-structure interaction methods coming from the O&G industry. The level of accuracy of these solvers has to be questioned in order to optimize the design of floating wind turbines or to avoid design mistakes. The objective of this paper is thus to compare two families of numerical methods with experimental results obtained by the Plymouth university, the paper is part of the ISOPE 2023 "first Floating Offshore Wind Turbine (FOWT) comparative study" session.

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