ECN has a long tradition in the development of aerodynamic design tools. In order to increase the accuracies of the design tools and to keep the computational time reasonable, the tools are based on a thorough under-standing of the physics phenomena on rotating rotors.

Theoretical and experimental investigations – Theoretical aerodynamics research is partly based on the results of international measurement campaigns on rotor aerodynamics. ECN co-ordinates a world-wide consortium through the IEA Annex Mexnext to investigate these data. Further theory development and the development of aerodynamic design software, the use of experimental results is required for the improved understanding of rotor aerodynamics.

Development of design software – apart from the required developments in BEM modelling, an aerodynamic free wake model based on lifting line panel method (AWSM) has been developed. A new code is being developed where also the boundary layer is being modelled. This method where the external pressure field of the rotating panel method that includes the wake is combined with a three dimensional unsteady boundary layer model will lead to an accurate method that is significantly faster than full Navier-Stokes field solvers (Rotorflow). In a Dutch consortium ECN has developed the RFOIL 3D code, a modified version of the XFOIL software.

Computational Fluid Dynamics (CFD) – the use of CFD technology in the context of rotor aerodynamics is relatively new. However, this research field develops fast. The modelling of rotors, preferably rotating rotors, using these techniques will lead to large improvements in the understanding of rotor aerodynamics. The calculation times of these models typically are extremely large, so that advanced methods must be designed in order to apply it to rotor aerodynamics. From the one end, commercially available software is applied in a variety of research activities, on the other dedicated CFD algorithms are developed.

Applications – The in-house developed codes are used for a better description of future large rotor blades of wind turbines leading to innovative ideas and techniques to improve the aerodynamic turbine operation. Especially the rotors currently under design in industry require dedicated and reliable tools. Research in the area of distributed control along rotor blades is related to the synthetic jets development. ECN holds a patent on the use of synthetic jets. The synthetic jets can reduce mechanical loading and are tested successively when non-rotating, rotating to scale and rotating in the field.