Small Darrieus vertical-axis wind turbines (VAWTs) have recently been proposed as a\npossible solution for adoption in the built environment as their performance degrades less in complex\nand highly-turbulent flows. Some recent analyses have even shown an increase of the power coefficient\nfor the large turbulence intensities and length scales typical of such environments. Starting from these\ninsights, this study presents a combined numerical and experimental analysis aimed at assessing the\nphysical phenomena that take place during the operation of a Darrieus VAWT in turbulent flows.\nWind tunnel experiments provided a quantification of the performance variation of a two-blade VAWT\nrotor for different levels of turbulence intensity and length scale. Furthermore, detailed experiments\non an individual airfoil provided an estimation of the aerodynamics at high turbulence levels and\nlow Reynolds numbers. Computational fluid dynamics (CFD) simulations were used to extend the\nexperimental results and to quantify the variation in the energy content of turbulent wind. Finally,\nthe numerical and experimental inputs were synthetized into an engineering simulation tool, which\ncan nicely predict the performance of a VAWT rotor under turbulent conditions.
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