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23/06/2009 – CLRC 2009 Pulsed Doppler Lidar wind profile measurement process in complex terrain Matthieu Boquet, Bruno Ribstein, Rémy Parmentier, Jean-Pierre.

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Presentation on theme: "23/06/2009 – CLRC 2009 Pulsed Doppler Lidar wind profile measurement process in complex terrain Matthieu Boquet, Bruno Ribstein, Rémy Parmentier, Jean-Pierre."— Presentation transcript:

1 23/06/2009 – CLRC 2009 Pulsed Doppler Lidar wind profile measurement process in complex terrain Matthieu Boquet, Bruno Ribstein, Rémy Parmentier, Jean-Pierre Cariou LEOSPHERE SAS – Centre Scientifique dOrsay - France

2 Lidar measurement in complex terrain 2 23/06/09 – CLRC 2009 Agenda Pulsed Lidar volume measurement principle Simple & complex terrain CFD modeling example Optimization Conclusions

3 Lidar measurement in complex terrain 3 23/06/09 – CLRC 2009 Pulsed Lidar principle HOW DOES THE WINDCUBE TM RETRIEVE WIND VELOCITY VERTICAL PROFILES?

4 Lidar measurement in complex terrain 4 23/06/09 – CLRC 2009 Volume measurement Radial velocity along a LOS Pulse FWHM probed sample Conically scanning d c =height*tanθ Sequentially scanning 4sec complete rotation v s = v.cos( ) Laser shooting direction aerosols

5 Lidar measurement in complex terrain 5 23/06/09 – CLRC 2009 Wind velocity vertical profile 4 radial velocities 3 wind velocity components Hypothesis: Same wind inside the probed volume Same wind at the 4 probed domains Stationary atmosphere Comparison with anemometers point measurement

6 Lidar measurement in complex terrain 6 23/06/09 – CLRC 2009 Terrain influence HOW WELL DOES THE WINDCUBE TM RETRIEVE WIND VELOCITY VERTICAL PROFILES?

7 Lidar measurement in complex terrain 7 23/06/09 – CLRC 2009 Flat terrain Inferior to 1% relative difference between Lidar and cup anemometer

8 Lidar measurement in complex terrain 8 23/06/09 – CLRC 2009 Forested area and gentle slope WindCube TM Forest Terrain slope over 10° About -2% relative difference between Lidar and sonic anemometer

9 Lidar measurement in complex terrain 9 23/06/09 – CLRC 2009 Mountainous terrain About -5% relative difference between Lidar and cup anemometer

10 Lidar measurement in complex terrain 10 23/06/09 – CLRC 2009 CFD Modeling analysis USING A CFD MODELING OF A COMPLEX TERRAIN TO BETTER UNDERSTAND THE LIDAR AND ANEMOMETER DIFFERENCES?

11 Lidar measurement in complex terrain 11 23/06/09 – CLRC 2009 CFD modeling MERCURE/Aria Technologies software Adapted to complex topography Fine meshing 2x2x1km box ~10x10x5m cells Stationary not a time variation study Fair enough to study Lidar wind velocity retrieval process under various local complex flow MatLab analysis Lidar measurement process simulation

12 Lidar measurement in complex terrain 12 23/06/09 – CLRC 2009 Spanish site Met mast WindCube North-West wind

13 Lidar measurement in complex terrain 13 23/06/09 – CLRC 2009 Wind distribution at 80m height North-west wind

14 Lidar measurement in complex terrain 14 23/06/09 – CLRC 2009 Overestimation >5% Underestimation <-5% North-West Wind Lidar vs. cup

15 Lidar measurement in complex terrain 15 23/06/09 – CLRC 2009 Back to the Lidar equations Considering first order wind speed variation Introducing wind speed gradient θ being the zenithal angle, d=height*tanθ is the probed volume to center distance In 2D:

16 Lidar measurement in complex terrain 16 23/06/09 – CLRC 2009 Vertical wind speed gradient dependency

17 Lidar measurement in complex terrain 17 23/06/09 – CLRC 2009 Geometrical Optimisation HOW CAN WE MODIFY THE LIDAR MEASUREMENT PROCESS TO GET CLOSER TO CUP?

18 Lidar measurement in complex terrain 18 23/06/09 – CLRC 2009 Reducing the scanning cone Probing a smaller volume then more homogeneous: Often but not always true Difference depends on altitude and vertical wind speed gradient Other issue: smaller horizontal wind speed projection higher noise perturbation No magical scanning cone angle Dangerous below 15° and above 30°

19 Lidar measurement in complex terrain 19 23/06/09 – CLRC ° vs. 15° 30°15°

20 Lidar measurement in complex terrain 20 23/06/09 – CLRC 2009 Multiplying the lines of sight Consider vertical wind speed linear variations A line of sight LOS i gives the radial velocity S i : With And Thus No LOS brings info on W i

21 Lidar measurement in complex terrain 21 23/06/09 – CLRC 2009 Conclusion Point and volume measurement Vertical wind speed inhomogeneity Scanning cone angle 15°-30° More lines of sight are not more useful info Experimental set up difficult

22 Lidar measurement in complex terrain 22 23/06/09 – CLRC Thank you


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