The specific objectives with this part of the project have been:
a) Derive and investigate 3D airfoil characteristics from a full scale MW rotor on basis of blade surface pressure measurements at 4 radial stations in combination with local inflow measurements with five hole pitot tubes at the same radial positions. Compare the 3D airfoil characteristics with 2D wind tunnel data and use the data sets for validation and further development of models for 2D to 3D conversions.
b) Investigate the influence of different aerodynamic devices such as vg´s, gurney flaps and roughness/transition elements on the pressure distributions.
A new LM38.8 m blade was manufactured for the NM80 80m diameter turbine and during the production process, equipment for measuring surface pressure profiles and inflow at four radial stations was placed inside the blade, Figure 1 Additionally, the most outboard blade section was instrumented with around 60 microphones to measure high frequency surface pressure spectra Figure 2. These data are used for determination of position of transition and for aeroacoustic characterization of inflow noise and trailing edge noise from the turbulent boundary layer. At a radial position close to the microphones, high frequency inflow has in a few campaigns been measured with a hot wire probe and with a pitot tube with microphones. Local inflow was measured at four radial positions with five hole pitot tubes.
Figure 1. Sketch of the instrumented LM38.8 m blade to the left and to the right the NM80 turbine with the test blade installed on May 13 2009
Figure 2. To the left: about sixty microphones were installed about one mm below the blade surface at the outboard section at radius 37 m for high frequency surface pressure measurements. The boring from the microphones to the blade surface has a diameter of 1.5 mm. To the right: every evening all pressure taps, microphones and five hole pitot tubes were covered with tape to protect against moisture and rain