Abstract
The paper presents the results of a computational study on the aerodynamics and the performance of a small-scale Vertical-Axis Wind Turbine (VAWT) for distributed micro-generation. The complexity of VAWT aerodynamics, which are inherently unsteady and three-dimensional, makes high-fidelity flow models extremely demanding in terms of computational cost, limiting the analysis to mainly 2D or 2.5D Computational Fluid-Dynamics (CFD) approaches. This paper discusses how a proper setting of the computational model opens the way for carrying out fully 3D unsteady CFD simulations of a VAWT. Key aspects of the flow model and of the numerical solution are discussed, in view of limiting the computational cost while maintaining the reliability of the predictions. A set of operating conditions is considered, in terms of tip-speed-ratio (TSR), covering both peak efficiency condition as well as off-design operation. The fidelity of the numerical predictions is assessed via a systematic comparison with the experimental benchmark data available for this turbine, consisting of both performance and wake measurements carried out in the large-scale wind tunnel of the Politecnico di Milano. The analysis of the flow field on the equatorial plane allows highlighting its time-dependent evolution, with the aim of identifying both the periodic flow structures and the onset of dynamic stall. The full three-dimensional character of the computations allows investigating the aerodynamics of the struts and the evolution of the trailing vorticity at the tip of the blades, eventually resulting in periodic large-scale vortices.
Highlights
Today, converting wind energy into electricity is one of the most relevant renewable technologies, and the available predictions of the energy scenario for the 30 years agree in forecasting a further growth of electricity generation by wind turbines
This paper presented a computational study of the flow around a lift-driven H-shaped Vertical-Axis Wind Turbine (VAWT) at two operating conditions: one for a tip speed ratio close to that of maximum power coefficient and another at a considerably higher tip speed ratio
The simulations benefit from a novel mathematical set-up that allows one to perform fully 3D simulations of the flow around the rotor and of the wake development with an industrially-relevant computational cost; an achievement still missing in the literature
Summary
Today, converting wind energy into electricity is one of the most relevant renewable technologies, and the available predictions of the energy scenario for the 30 years agree in forecasting a further growth of electricity generation by wind turbines. Higher fidelity methods based on Computational Fluid Dynamics (CFD) have been applied to VAWTs, obtaining physically-sound representations of the flow field around the rotor [3,4,5,6,7], as well as quantitatively reliable performance estimates [8]. Such simulations cause very high computational cost that has historically led the researchers to employ simplified actuator-line [9] or 2D flow models, with proper correction terms added to account for strut and tip losses. Conclusions are drawn on the most relevant flow structures, in view of performance improvement at design and off-design operation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
