Abstract

Turbulence statistics were applied to the downwind flow of a Darrieus-type vertical axis wind turbine (VAWT) to provide insights about VAWT micro-flow characteristics. Micro-turbulence measurements of the flow in front of and behind a VAWT were made using a sonic anemometer. Turbulence data for downwind distances of 0.5 m and 2.0 m from the wind source were collected with and without the VAWT, respectively, using a blower (Type 1 flow) and industrial fans (Type 2 flow) as the wind source. The voltage V, generated by the VAWT was recorded every 15 min. Only the center line of the flow was considered. The Type 2 flow induced a constant spectral power at a high dimensionless frequency range of 0.007 < f < 0.04, perhaps due to the fan configuration, which had a larger wind-swept area. The results show an increase in lateral turbulence, ?_v, downwind of the VAWT compared to its longitudinal, ?_u, and vertical, ?_w, counterparts. Using spectral analysis, the VAWT was found to reduce the horizontal (u and v) turbulent component energies in the dimensionless frequency range of 0.003–1. Interesting dip and peak features were observed for Type 1 flow, but only dip features were observed for Type 2 flow in the resulting spectra. Higher wind speeds increased the voltage generated at a rate of 0.5.

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