The dynamic simulation of offshore wind turbines requires an integrated approach taking into account the aerodynamics, the hydrodynamics, the structural and mooring dynamics and the control strategy in a coupled manner. CENER has a wide experience in integrated simulation that has applied to the design, the analysis and the certification of different wind turbine concepts. CENER takes part in the International Energy Agency (IEA) Annexes 23 and 30 since 2007. In addition, CENER has developed its own in-house tools for numerical simulation of offshore wind energy systems. These numerical models have different complexity levels to be applied at different design stages and to perform both preliminary and detailed analysis.
Multi wind turbine simulation tool (MUST)
MUST is an in-house development based on OpenFAST . It is designed to allow the simulation of more than one wind turbine (Tower, Rotor, Nacelle) installed on a floating platform, following the work by .
MUST has been coupled to a CENER in-house aerodynamic module, AeroVIEW ,  (Aerodynamic Vortex fIlamEnt Wake), that is able to capture the aerodynamic interaction between nearby rotors in aeroelastic simulations and also the interaction between the rotor with its own wake.
 NREL, 2019. “OpenFAST Documentation”.
 Bae, Y., 2013. “Coupled dynamic analysis of multiple unit floating offshore wind turbine”. PhD. Dissertation, 53 (May).
 Martín-San-Román R, Azcona-Armendáriz J and Cuerva-Tejero A. “Lifting line free wake vortex filament method for the evaluation of floating offshore wind turbines. First step: validation for fixed wind turbines”. In IWOTC, ASME 2019 2nd International Offshore Wind Technical Conference.
 Martín-San-Román R, Benito-Cia P, Azcona-Armendáriz J and Cuerva-Tejero A.“Validation of a free vortex filament wake module for the integrated simulation of multi-rotor wind turbines”. Renewable Energy,179, pp. 1706–1718, 2021.
Computerized Fluid Dynamics
Computational Fluid Dynamics (CFD) is a numerical method of simulating fluid motion, steady and unsteady, based on the Navier-stokes equations. CFD simulation is a well-established methodology often used to replace or supplement experimental methods to aid the engineering design and analysis. It is known as the most accurate simulation computational model, and the fidelity of the model can be adjusted to the particular application and computing resources available.
cenerFoam is a CFD simulation software, based on OpenFOAM, developed by CENER to support the optimization of floating wind turbines. The CFD hydrodynamic characterization of wind turbine platforms results on faster and cheaper optimization processes for platform developers.
Compared to other optimization methods, CFD simulations:
- Are less expensive and faster
- Can simulate more complex phenomena than experiments
- Can explore multiple designs and scenarios
- Provide deep understanding on the fluid physics
Scaled wave tank testing of floating wind turbines is an important step in the design process in order to reduce risks and validate simulation tools. An accurate representation of the forces involved in the platform dynamics is key to obtain reliable measurements. Sorting the conflict between the hydrodynamic and aerodynamic scaling rules is one of the most important technical challenges in these kind of tests. CENER has developed a hybrid method to include a realistic coupled rotor force during the tests. It is called the Software-in-the-Loop method (SiL).
The scaled floating platform test method was initially based on a single actuator to simulate the wind thrust, however, this simplification did not allow simulating all the loads and moments on a coupled wind turbine – platform. For this reason, CENER has developed an innovative methodology that overcomes this limitation and that we present in the video.
We want to highlight the support of MARIN (Netherlands) in the validation of this innovative methodology. MARIN contributed its experience, professionalism and made its facilities available to us throughout the process.
Mooring line Analysis and Design
The design of the mooring system of a floating wind turbine has an important impact on the system natural frequencies, stability, dynamics and load level. CENER has developed its own mooring system dynamics numerical model called OPASS. The code has been experimentally validated with tension and motion measurements of an scaled mooring line in a wave tank. OPASS has been applied to the design of many mooring systems and loads analysis.
The substructure of an offshore wind turbine is one of the most expensive components of the system. The optimization of the design is key to reduce the cost of the energy. The design is highly coupled with the rest of components, and an integrated approach is required. CENER has developed the design of the DELTA-Wind platform for a 10MW floating wind turbine. It is an open, publicly available design including the structural scantling. This platform is the reference design for the MARINET 2 wave tank Round Robin, and will be tested in the following years in 4 different European wave tanks.