The main objective of the fourth phase of IEA Wind Task 29 is to validate, improve and develop aerodynamic models for wind turbine design codes. More specifically models will be validated and improved for the following aspects:
- Aerodynamic response to turbulent inflow
- Sheared inflow
- 2D/3D aerodynamics
- Aeroelastic effects
- Transition characteristics in realistic flow conditions
Different categories of models will be considered (CFD, free wake methods, engineering methods etc.).
The model assessment will largely, but not exclusively, be based on the detailed aerodynamic measurements taken on an NM80 2MW turbine from the Danish DanAero field experiment. The data from this experiment have been made available to the Task 29 group by the DanAero consortium.
The most important outcomes of phase IV will be:
- Improved and validated aerodynamic and aero-elastic models for wind turbine design codes leading to improved insights on e.g. dynamic induction and transition effects, in atmospheric inflow
- A detailed plan for a new large scale aerodynamic field experiment
- A user friendly validation platform built around the calculational cases from all IEA Task 29 phases.
Moreover the quality of the measurement data base will be improved: experiences from the previous IEA Tasks have taught us that a thorough analysis of measurement data also leads to high quality validation of the experimental data itself (e.g in Mexnext-II a need for recalibration of the Mexico experiment was identified).
The approaches in all four phases of Task 29 are similar although the fact that the first three phases are devoted to wind tunnel measurements, where the fourth phase is devoted to field measurements gives different focal points (e.g. the first phases investigated tunnel effects and PIV flow field measurements where the fourth phase puts emphasis on aero-elastic effects and turbulent inflow). Still in all phases there are Work Packages devoted to processing of measurements including an analysis of measurements uncertainties, a comparison of calculations and measurements and a deeper investigation of aerodynamic phenomena using the detailed measurements. Moreover the fourth phase of Task 29 includes the design of a large scale aerodynamic field experiment (even larger than the DanAero experiment) and a connection to the previous Task 29 phases which provided valuable information on aerodynamic modelling as well from wind tunnel measurements. As a matter of fact wind tunnel and field measurements should be seen as complementary.
Measurements in the field can be done on representative full size turbines and as such the inevitable scaling effects in a wind tunnel environment are avoided where the atmospheric conditions are representative of the conditions which are experienced on a commercial wind turbine. On the other hand, the stochastic nature of atmosphere, though representative, makes interpretation of results more complicated where extremes and faulty conditions (e.g. extreme yaw) cannot be controlled but they need to be catched ‘’by accident’. The best strategy to improve aerodynamic knowledge is then to combine the insights from full scale field measurements with those from wind tunnel measurements. Apart from the interaction to previous Task 29 Phases on wind tunnel measurements, an activity is included to disseminate information on aerodynamic modelling to other IEA Tasks with connections to aerodynamics.