| Summary: | To properly conduct a micro-siting of an orthopter-type vertical axis wind turbine (O-VAWT) in the built environment, this study investigated the effects of horizontal shear flow on the power performance characteristics of an O-VAWT by performing wind tunnel experiments and computational fluid dynamics (CFD) simulations. A uniform flow and two types of shear flow (advancing side faster shear flow (ASF-SF) and retreating side faster shear flow (RSF-SF)) were employed as the approaching flow to the O-VAWT. The ASF-SF had a higher velocity on the advancing side of the rotor. The RSF-SF had a higher velocity on the retreating side of the rotor. For each type of shear flow, three shear strengths (<i>Γ</i> = 0.28, 0.40 and 0.51) were set. In the ASF-SF cases, the power coefficients (<i>C<sub>p</sub></i>) were significantly higher than the uniform flow case at all tip speed ratios (<i>λ</i>) and increased with <i>Γ</i>. In the RSF-SF cases, <i>C<sub>P</sub></i> increased with <i>Γ</i>. However, when <i>Γ</i> = 0.28, the <i>C<sub>P</sub></i> was lower than the uniform flow case at all λ. When <i>Γ</i> = 0.51, the <i>C<sub>P</sub></i> was higher than the uniform flow case except at low λ; however, it was lower than the ASF-SF case with <i>Γ</i> = 0.28. The causes of the features of <i>C<sub>P</sub></i> were discussed through the analysis of the variation of blade torque coefficient, its rotor-revolution component and its blade-rotation component with azimuthal angle by using the CFD results for flow fields (i.e., horizontal velocity vectors, pressure and vorticity). These results indicate that a location where ASF-SFs with high <i>Γ</i> values dominantly occur is ideal for installing the O-VAWT.
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