REDUCED ORDER MODELING OF LOADS ON A VERTICAL AXIS WIND TURBINE

Abstract

The growing concern for the environment has led to the search for more environmentally friendly energy sources. A viable option is wind energy. With global attention on exploring cost-effective wind energy based power generation techniques, vertical axis wind turbines (VAWT) have emerged as a best option for urban roof top applications. Computation of loads on a turbine plays an important role in turbine design and determining the output power. For an optimum design, experimental setup can be a viable solution. However due to huge cost associated with experiments, numerical techniques provide an alternate solution for computing loads on the turbine. However, for a systematic sweep over parametric range, numerical simulation would require thousands of CPU hours or even more. Thus, reducedorder models are often developed instead of high-fidelity solutions. In this thesis, we performed two dimensional numerical simulations of the flow over a VAWT which have three Darrieus H type blades by using a computational fluid dynamics (CFD) solver. Symmetric air foils NACA0022 having chord length of 0.2 meter were used as blades of the wind turbine. The steady state torque obtained through CFD is used to develop reduced-order model, which is based on van der Pol Oscillator. Effect of third dimensionality on reduced order model was also studied. The analytical model captures the steady state region of torque both in temporal and spectral domain. The work done here is a step towards the construction of models for (VAWT) that have emerged as a promising option for urban roof top applications.