The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.

We have determined the normal Reynolds stresses and spectra of the wind velocity over a 1:115 scale mock-up of the Bolund hill. The experiment was run in a neutral boundary layer wind tunnel using 3-component hot-wire velocimetry, 2-component particle image velocimetry, and a high-precision traversing system. Spectra have been determined at different points along transects at 2 and 5 m height above ground level. The experiment was run for 270 • wind direction and for two Reynolds numbers, Re h 1 = 4.25×10 4 and Re h 2 = 8.21×10 4 , based on the maximum height of the hill and the free wind speed at this height. Our results show how the normalized power spectral density S ii = fS ii ∕u 2 i changes over the hill. The analysis of the normalized streamwise spectrum at 2 m height, just after the escarpment, reveals that part of the energy is concentrated in the interval of normalized frequencies n h ≈ 0.01 − 0.02, which could be a signature of a weakened "flapping" phenomenon described in the literature for flows over forward facing steps. The departure of the spectra slope in the inertial subrange, from the value −5/3, was found to be correlated with the hill geometry. KEYWORDS atmospheric boundary layer, complex terrain, wind energy, wind tunnel simulation 1 INTRODUCTION The Bolund experiment, run by RISØ-DTU in 2007, is probably the most relevant test case of flow models oriented to wind energy analysis over highly complex terrains, in neutral conditions and nonaffected by Coriolis forces. 1,2 Bolund is a reference case to identify flow patterns and to validate numerical and physical models, due to the number and quality of sensors installed on the full-scale hill and the amount of numerical and physical analyses available such as literature. 1-6 Bolund is a small hill of about 130 m × 75 m × 12 m, surrounded by water with a long uniform fetch for most of the upstream directions of interest (see Figure 1-left). A large amount of periods with nearly neutral atmospheric conditions can be found in the full-scale database provided by RISØ-DTU. These characteristics convert Bolund into an ideal case for wind tunnel modeling without considering flow stratification effects.The escarpment facing westerly winds is one of the main geometric characteristics of Bolund (see Figure 1). The escarpment height varies slightly for the 200 • to 295 • wind direction interval, being roughly equal to the maximum height of the island, h = 11.73 m. Flow detachment at the escarpment has been observed in the full-scale experiment 1,7 and in wind tunnel tests. 4,8 Reproducing the flow characteristics in this region has revealed to be a challenge, particularly at lower heights, where the interaction between the turbulent inflow and the detachment dynamics is highly complex. Most of the numerical and physical models have failed to reproduce the high reduction in the mean wind speed and the high increment in the turbulent kinetic energy (TKE) found in the full-scale experiment in met mast M6 at 2 m height for 270 • wind direction, see Figure 2. ...

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