THE PURPOSE OF THIS RESEARCH IS TO OBTAIN A BETTER UNDERSTANDING OF THE TURBULENT WIND STRUCTURE OVER A HILL SURROUNDED BY A COMPLEX TERRAIN.
A field experiment was carried out at Lastours, a large hill in the south of France, where a small wind farm was set up. The Lastours site hill is situated near the Mediterranean coast at 20 km to the southwest of Narbonne. The prevailing wind, Tramontana, blows from a strong hilly country with a mean altitude of 150 m. Downwind of the hill, the relief decreases quickly towards the seashore plain. An oreographic map of the hill has been produced on 2 different scales.
3 masts were erected on the top of the hill that make up a vertical plane perpendicular to prevailing winds (exact direction 287 degrees). The central 40 m tower was equipped at 4 levels (4, 10, 23.5, 40 m) with Gill propeller UVW anemometers, the W component being in the vertical. In addition, a Doppler sodar REMTECH was set up on the top of the hill to obtain an upper vertical wind profile that we were able to use as a reference. Unfortunately, during the experiment, the wind speed was too high to have sodar data available. The vertical temperature gradient was also measured with 3 ventilated platinum sensors to provide an estimate of the local atmospheric stability.
AFTER A BIBLIOGRAPHICAL STUDY WHICH HAS SHOWN A LACK OF DATA, A FIELD EXPERIMENT HAS BEEN CARRIED OUT AT LASTOURS, A LARGE HILL IN THE SOUTH OF FRANCE, WHERE A SMALL WIND FARM IS SETTLED UP. THE SITE IS A SMALL BARREN PLATEAU (ALT. 300 M) WITH STEEPY SLOPES SURROUNDED BY A HILLY COUNTRY. THREE MASTS EQUIPPED WITH THREE DIRECTIONAL GILL PROPELLER ANEMOMETERS AT DIFFERENT LEVELS (4, 10, 24 AND 40 M) WERE SET UP IN A PLANE PERPENDICULAR TO THE PREVAILING WIND.
THE COLLECTED SAMPLES OF WIND SPEED GIVE SOME TURBULENCE AND SPECTRAL CHARACTERISTICS OF THE FLOW OVER THE PLATEAU : THE MEAN WIND SPEED PROFILE IS WELL EXPLAINED IN THE LOWER PART OF THE BOUNDARY LAYER BY THE PERTURBATION THEORY OF FLOW OVER HILL (TESTED BY THE MEAN OF THE NUMERICAL MODEL MS3DJH/3R). THE LONGITUDINAL IS CLOSE TO VALUES ON FLAT HOMOGENEOUS TERRAIN, BUT LATERAL TURBULENCE IS OF A STRONGLY HIGHER LEVEL. KAIMAL'S SPECTRAL FORMULATION FITS THE OBSERVED POWER SPECTRA IN THE INERTIAL SUBRANGE BUT AT LOWER FREQUENCIES ENERGY RECOVERY CAN BE OBSERVED.