This report describes the final results of the fourth phase of IEA TCP Wind Task 29. The project period of this fourth phase was from January 1 st 2018 until December 31 st 2020. It was the follow-up of three former IEA Task 29 phases (often denoted as Mexnext-I to Mexnext-III). In all phases wind turbine aerodynamic models were validated and improved with detailed aerodynamic measurements. In these detailed aerodynamic experiments pressure distributions at different locations along the rotor blades are measured anyhow where measurements of e.g. inflow velocities and boundary layer transition are very nice to know. The first three phases were mainly built around wind tunnel measurements on a small scale wind turbine with rotor diameter of 4.5 meter from the (New) Mexico project but the present phase was built around field measurements from the DanAero experiment. This DanAero experiment was carried out at atmospheric field conditions on a 2MW turbine by Danish Technical University DTU and 4 industrial partners (LM Glassfiber, Siemens WindPower, Vestas and Dong Energy) in 2 periods from 2007 until 2010 and from 2010 until 2013. Amongst others surface pressures and inflow velocities were measured at four sections along a blade and a row of surface flush mounted microphones was installed at the outer part ofthe blade. In IEA Task29 Phase IV the DanAero data were made available to the IEA Task 29 participants which enabled a detailed analysis in a collaborative action. Amongst others a critical scrutinising of data took place with subsequent further improvement of measurement quality. Moreover the measurements were used as validation material for the many design models which are available in the consortium. A wide variety of models could be considered ranging from high fidelity (but time consuming) CFD to lower fidelity but efficient engineering models. Intermediate methods (e.g. free wake methods) were applied as well. Several calculational rounds were carried out where calculations were compared with measurements. Amongst others a case was defined at simple steady and axi-symmetric conditions close to a measurement case with little shear and little yaw but also measurement cases at high yaw and high shear were simulated. Moreover the level of detail from the DanAero experiment allowed an in-depth analysis of several wind turbine aerodynamic aspects, e.g.

• Aerodynamic response to turbulent inflow;
• Sheared inflow;
• 2D/3D aerodynamics;
• Aeroelastic effects
• Transition characteristics in realistic flow conditions;
• Acoustics.

The project was carried out by a consortium which consisted of research groups and industries from 9 different countries

• China: Chinese Wind Energy Association, CWEA
• Denmark: Technical University of Denmark, DTU, Siemens-Gamesa Renewable Energy
• France: IFPEn, LHEEA lab - Centrale Nantes/CNRS, ONERA, EDF
• Germany: ForWind/Fraunhofer IWES, Kiel University of Applied Sciences, University of Stuttgart, WindNovation, Enercon Deutsches Zentrum für Luft- und Raumfahrt e.V., DLR University of Applied Sciences Emden
• Italy: PoliMi, RSE, CNR - INM
• Netherlands: TNO Energy Transition (formerly ECN, Operating Agent), Delft University of Technology, TUDelft, DNV-GL Suzlon Blade Technology, SBT, CWI, LM and University of Twente, UTwente
• Italy: PoliMi, RSE, CNR - INM
• Sweden: Uppsala University, Campus Gotland
• Switzerland: UAS Rapperswil
• USA: National Renewable Energy Laboratory, NREL