Reduced Order Modeling of Loads on a Vertical-Axis Wind Turbine

In this paper, we develop a reduced-order model of the torque produced by a vertical-axis wind turbine (VAWT) at different tip speed ratio (TSR). We numerically simulate the flow past a three-bladed Darrieus H-type VAWT to compute overall torque acting on the turbine. We then perform spectral analysis to compute the dominant frequencies and their interaction. Numerical results are used to analyze the coupling of various frequency components in aerodynamic torque signal and to develop a reduced-order model based on van der Pol oscillator. The proposed model approximates the temporal histories and their spectra accurately. The work performed here is a step towards application of VAWT for urban buildings and roof-top applications. These reduced-order models will provide a means to predict overall performance and output of the turbine with varying free-stream conditions.