Vertical-Axis Wind Turbines are receiving the attention of the wind energy community for urban wind harvesting. However, their practical application is still far from maturity, due to the lack of understanding of urban flows. High turbulence is one of the main characteristics of wind in complex environments, so special attention has been paid to modelling it inside wind tunnels for prototype testing. Previous experiments showed a considerable boost in VAWT performance when turbulence intensity increases, but the explanation of this increase still has to be determined. This study analyses the effect of turbulent flows on the performance of a NACA0018 airfoil, using a blade model provided with pressure tabs and a traverse system to analyze the wake. The model is subjected to the same angles of attack and Reynolds numbers that would be found in normal VAWT operation, while turbulence intensity and integral length scale are kept at levels similar to those found in urban environments. The effect of turbulence is evident as it considerably delays the stall angle of the blade. Using a Single Streamtube model, the results from this parametric study are compared with the overall turbine ratings, in order to find a way to optimize turbine blades using a simplified set-up.
Experimental Characterization of VAWT Airfoils Under Turbulent Flows / Carbo Molina A.; Van de Maele S.; Bartoli G.; De Troyer T.; Runacres M.. - ELETTRONICO. - 8:(2019), pp. 21-38. (Intervento presentato al convegno Colloquium on Research and Innovation on Wind Energy on Exploitation in Urban Environment (TUrbWind 2018) tenutosi a Riva del Garda (Italy) nel September 6-7, 2018) [10.1007/978-3-030-13531-7_2].
Experimental Characterization of VAWT Airfoils Under Turbulent Flows
Carbo Molina A.;Bartoli G.;
2019
Abstract
Vertical-Axis Wind Turbines are receiving the attention of the wind energy community for urban wind harvesting. However, their practical application is still far from maturity, due to the lack of understanding of urban flows. High turbulence is one of the main characteristics of wind in complex environments, so special attention has been paid to modelling it inside wind tunnels for prototype testing. Previous experiments showed a considerable boost in VAWT performance when turbulence intensity increases, but the explanation of this increase still has to be determined. This study analyses the effect of turbulent flows on the performance of a NACA0018 airfoil, using a blade model provided with pressure tabs and a traverse system to analyze the wake. The model is subjected to the same angles of attack and Reynolds numbers that would be found in normal VAWT operation, while turbulence intensity and integral length scale are kept at levels similar to those found in urban environments. The effect of turbulence is evident as it considerably delays the stall angle of the blade. Using a Single Streamtube model, the results from this parametric study are compared with the overall turbine ratings, in order to find a way to optimize turbine blades using a simplified set-up.
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