1 LASER MEASUREMENTS OF WAKE DYNAMICS RISØ National Laboratory / DTU Roskilde DENMARK 9th May 2007 Ferhat BingölJakob MannGunner C. Larsen

2 A New Anemometer remote sensing instruments... Høvsøre Nysted

3 Conical Scanning Mode Original Working Mode of ZephIR 25 points on each height l H φ 1 round = 1 second 3 rounds give 1 good data It can change focus distance in 1 sec φ=30 o (Azimut angle) θ=[0:π/2] (scanning angle) Max height = 200m Min height = 5m -φ-φ u

4 Conical Scanning Mode A B CD u C A B D

5 Reliability

6 Development and Experiments at Risø

7 Different Experiment Models

8 Removing the wedge With the wedgeWithout the wedge The wedge from leftThe wedge

9 Staring Mode p’

10 An add-on : Tilt and Pan Head The Lidar can be mounted onto the Head and controlled

11 Simple Line Scanning Mode derived from the Staring Mode and the movement of the Head in pan direction captures data from points on an arc. P1P1 P2P2 P1P1 P2P2

12 Deep Line Scanning Mode derived from the Staring Mode and the movement of the Head in pan and tilt direction by changing the focus distance P1P1 P2P2 P3P3 P4P4 P5P5 P6P6 P1P1 P2P2 P3P3 P4P4 P5P5 P6P6

13 2D Scan

14 2D Scan Path

15 Experimental Setup

16 ZephIR on Tellus

17 Experiment area New MM Old MM Nordtank 500kW Tellus 100kW

18 Data collection & selection T/MChannelHeight MM1WS WD Temperature Pressure Rain 35m 36m 3m - MM2WS WD 29.3m 19.7m 29.3m 35m TellusWSN WDN Power YM 35m - NordtankWSN Power RPM Status 29m -

19 ZephIR on Operation

20 Results

21 Software tune-up ZephIR LabView software works at 20 Hz in conical scanning and staring mode 15 Hz in any multi thread mode. We use C++ instead of LabView Multithreaded coding structure FFTW (Fastest Fourier Transform in the West)

22 Multi Thread Scanning Freq. Acquisition 36.8% Reading 15.9% FFT 46.6% Rest 0.8% improvement factor of 9 FFT size512 Number of Averages256 Samples per scan Acquisition36.8% Reading15.9% FFT46.6% Rest0.8% Scanning Frequency from 15Hz to 136 Hz

23 How does it help? 136 Hz 15 Hz Wind Speed [m/s] Cross Stream distance [m]

24 Simple Line Scanning Sample Line Scans at 72m

25 Deep Line Scanning Sample Line Scans at 19, 76, 130 and 176m

26 Synchronization with Met. Mast data*

27 Synchronization with Met. Mast data*

28 2D Scan

29 Conclusion We have developed a new measurement technique that allows both for a 1D and a 2D scanning of the instantaneous longitudinal wake velocity. Using this technique, we resolve the wake expansion in the moving frame of reference as well as the movements of the wake. Resolving the wake meandering dynamics allow us to verify a basic assumption for dynamic wake modeling - i.e. that the wake deficit is advected passively by the larger than rotor size eddies in the inflow. The present initial investigations seem to support this hypothesis for the investigated full scale turbine located in the atmospheric boundary layer.

30 THANK YOU ! Ferhat BİNGÖL