France forecasts 2400 MW produced by offshore wind turbines by 2023.
There is a strong need for tools capable of optimizing the position of the turbines within the farm: accurate definition of the loading to optimize the turbine structure; reduce the maintenance costs; better prediction of the energy production.
In this project, we provide an alternative approach: development of a CFD direct model, coupled to more simplified formulations to reduce the computational cost.
The analysis of the dynamics around a single offshore wind turbine (floating or not) is a challenge that involves the study of the strong interactions between its various components, such as blades, rotor, control or support systems. This requires multiphysical modeling that includes aerodynamics, hydrodynamics and structural mechanics. In addition, the extension of these studies to wind farms will also have to consider the interactions between several wind turbines, and in particular the wake effects. The changes in speeds (in air and water) and the levels of turbulence achieved affect the power generated by these farms and can increase loads in wind turbine structures placed downstream.
Today, the design tools used for wind farm design and the development of turbines are perfectible and essentially based on empirical formulations to take into account changes in turbulence level and wake interactions. In this context, the EOS project aims to develop an offshore wind farm simulator based on high-fidelity simulation for aerodynamic and hydrodynamic forces. To represent an offshore wind turbine and its environment as accurately as possible, models linked to several disciplines from the state of the art and work will be used and will include geometric elements (such as the floating support or rotor), but also physical conditions, such as waves or ocean-weather data. The access to high performance computing will be necessary in order to carry out the precise simulation of fluid (air) – fluid (water) – structure interactions that appear inside an offshore wind farm. This analysis will be used to understand the interacting phenomena, but also to feed simplified models used in engineering.
In conclusion, the main outcome of the EOS project will be the development of a numerical tool that will be useful in the medium- to long-term for the wind farm simulation sector, both for the development of control algorithms or the optimization of the layout of wind farms. This project will also improve the current understanding of fluid (aero-hydro) structure interactions and provide a database useful to the community for the development of new models.
Scientific advances and innovation
Nowadays, Offshore Wind Farms are designed using simplified models based on empirical formulations to take into account wakening and turbulence effects.
- Development of a direct model, without simplifications.
- Multiphase CFD massively parallel code, very scalable and associated to Pays de la Loire supercomputing facilities.
- Simulation platform which may be edited, diffused and valorized by a regional PME specialized in marine activities.
The main scientific advances concern the establishment of a full CFD approach: no simplifications, no hypothesis, good precision and interactions (like wakes) are implicitly taken into account.
To reduce the computational cost, techniques like automatic anisotropic mesh adaptation and massively parallel computing are implemented. It involves also the treatment of difficult topics like: the development of an aero-hydro coupled solver in an FSI context (floating and moving rigid body), the study of water/air/wind turbine interactions in the one and two wind turbine cases; the introduction far-field conditions and boundary conditions in the near-field domain.
In terms of innovation, a multiphase CFD massively parallel code, very scalable and associated to Pays de la Loire supercomputing facilities will arise.
Expected technical and economic impact
- Advanced knowledge of the behavior of individual floating wind turbines in a wind farm.
- Show an unique expertise in 3D accurate simulation of offshore floating wind turbines.
Key project milestones
- November 2016 - Kick-off
- January 2018 - Aerodynamic simulations and coupling
- January 2019 - Hydrodynamics simulations and coupling.
- November 2020 - Simulation platform for offshore wind farm dynamics
Simulation platform for offshore wind farm dynamics.
The simulator will be based on the ICI-tech library, developed by the High Performance Computing Institute (ICI-ECN) at the Ecole Centrale de Nantes and dedicated to high-performance scientific computing. The application of the developments carried out previously and the implementation in EOS for the simulation of one or more floating wind turbines will be guided by the Ocean and Marine Energy team at the Laboratory in Hydrodynamics, Energy and Environment Atmospheric (LHEEA-ECN), also at the Ecole Centrale de Nantes, and which will also participate in the fine validation of the simulator, in comparison with experimental results or other models from the literature and also through the participation to the IAEWind project.
- First CFD simulations with the existing solver
- Acceleration of computation of the phase functions to represent different domains in the simulation
- Parallel meshing of models up to 100 wind turbines
- Development of a wind simulator and FSI. Study of the main limitations.
- Development of a wave simulator and HOS coupling. Study of the main limitations.
- Starting of the software prototype development.
|First CFD simulations with the existing solver||Acceleration of computation of the phase functions to
represent different domains in the simulation
|Parallel meshing of models up to 100 wind turbines|
|Software prototype development||Wave simulator and HOS coupling||Wind simulator and FSI|
Publications and papers published
 L. Douteau, L Silva, H Digonnet, T Coupez, D. Le Touzé, JC Gilloteaux, Simulation numérique d’éolien offshore, Congrès Français de Mécanique, Lille (August 2017)
 L. Douteau, L Silva, H Digonnet, T Coupez, D. Le Touzé, JC Gilloteaux, Numerical simulation of floating wind turbine using anisotropic mesh adaptation, EAWE, Cranfield (September 2017). – Download the publication
 L. Douteau, L Silva, H Digonnet, T Coupez, D. Le Touzé, JC Gilloteaux, A monolithic and adaptive finite element method to simulate floating wind turbine dynamics, Simulation et Optimisation pour les Energies Marines Renouvelables, GDR EMRs, Paris (January 2018) – Download the abstract
 L. Douteau, L Silva, H Digonnet, T Coupez, D. Le Touzé, JC Gilloteaux, Towards offshore wind turbine numerical simulation using anisotropic mesh adaptation, Progress in CFD for wind and tidal offshore turbines, ECFD, Glasgow (June 2018).Read the publication
 L. Douteau, L Silva, H Digonnet, T Coupez, D. Le Touzé, JC Gilloteaux, Towards Numerical Simulation of Offshore Wind Turbines Using Anisotropic Mesh Adaptation, EAWE, Brussels (September 2018).
 L. Douteau, L Silva, H Digonnet, T Coupez, D. Le Touzé, JC Gilloteaux, Towards Numerical Simulation of Offshore Wind Turbines Using Anisotropic Mesh Adaptation, in CFD for Wind and Tidal Offshore Turbines, pp.95-104, Springer (2019)
 Douteau, L Silva, H Digonnet, T Coupez, D. Le Touzé, JC Gilloteaux, Towards Numerical Simulation of Offshore Wind Turbines Using Anisotropic Mesh Adaptation, French American Innovation Day 2019 (March 2019) – Download the poster
 H Digonnet, N Aissa, L Douteau and L Silva, Massively parallel anisotropic mesh adaptation applied to complex microstructures, Eccomas Thematic Conference on Adaptive Modelling and Simulation, ADMOS 2019 (May 2019) Download this publication
 L. Douteau, L Silva, H Digonnet, N. Aissa, A fast and parallel octree based method for multiphase flows (International Journal of High Performance Computing Applications, 2020)
 L. Douteau, L Silva, H Digonnet, T Coupez, D. Le Touzé, JC Gilloteaux, A monolithic finite element approach for IFS: application to floating structures (à soumettre, 2020)
- Douteau, Ecole Thématique du GDR EMR, Nantes (Octobre 2017).
- Silva, Journée EERA JP Wind, Ecole Centrale de Nantes (Mai 2018)
FSI for fluid / deformable structures; floating bodies (on-going); more accurate treatment of wake and boundary conditions.
Optimization: co-simulation with AI and ROM.