Some measurements of turbulence characteristics over complex terrain

Results are presented from a wind turbulence measurements campaign at the summit of a hill in complex terrain in Andros island (Greece) where a wind turbine park has been constructed. Mean turbulence parameters and power spectra from three 30 m masts located at the summit, upwind and downwind of the hill are analysed to ascertain the differences from respective parameters in flat terrain and to assess the influence of the irregular topography. The variances of the horizontal (vertical) wind components are found to be smaller (larger) than the ones from flat terrain. Of the available correlations for the power spectra, the Von Karman one was found to give better results, although the low frequency parts show pronounced lags. The asymmetry of the upwind terrain for different wind directions and especially its slope is clearly felt both by variances and by spectra. This influence, as expected, is found to increase with increasing stability. These results have an important significance for wind turbine design and wind energy utilisation. Key words: Wind flow, Complex terrain, Turbulence spectra, Turbulence measurements.