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LASER MEASUREMENTS OF WAKE DYNAMICS RISØ National Laboratory / DTU Roskilde DENMARK 9th May 2007. A New Anemometer. remote sensing instruments. Høvsøre Nysted. 2 5 points on each height. Conical Scanning Mode. Original Working Mode of ZephIR. 1 round = 1 second
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LASER MEASUREMENTS OF WAKE DYNAMICS RISØ National Laboratory / DTU Roskilde DENMARK 9th May 2007
A New Anemometer remote sensing instruments... Høvsøre Nysted
25 points on each height Conical Scanning Mode Original Working Mode of ZephIR • 1 round = 1 second • 3 rounds give 1 good data • It can change focus distance in 1 sec • φ=30o (Azimut angle) • θ=[0:π/2] (scanning angle) u H l -φ φ Max height = 200m Min height = 5m
Conical Scanning Mode C u B A D B A C D
With the wedge Without the wedge The wedge from left The wedge Removing the wedge
p’ Staring Mode
An add-on : Tilt and Pan Head The Lidar can be mounted onto the Head and controlled
P2 P1 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. P2 P1
P6 P4 P5 P2 P3 P1 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 P6 P2 P4 P1 P3 P5
3 1 2 4 5 6 Experimental Setup
Experiment area New MM Tellus 100kW Nordtank 500kW OldMM
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)
Rest 0.8% Acquisition 36.8% FFT 46.6% Reading 15.9% Multi Thread Scanning Freq. improvement factor of 9
How does it help? 136 Hz Wind Speed [m/s] Cross Stream distance [m] 15 Hz Wind Speed [m/s] Cross Stream distance [m]
Simple Line Scanning Sample Line Scans at 72m
Deep Line Scanning Sample Line Scans at 19, 76, 130 and 176m
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.
THANK YOU ! Ferhat BİNGÖL ferhat.bingoel@risoe.dk