The influence of aerodynamic stall on the performance of vertical axis wind turbines

• Main Author: Edwards, Jonathan
• Other Authors: Howell, Robert
• Published: University of Sheffield 2012
• Subjects: 621.4
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.559157

There is currently an increasing desire for local small-scale sustainable energy generation. This has lead to increased interest in the concept of the vertical axis wind turbine (VAWT), which is potentially well-suited to operation within the built environment. This study investigates the performance and flow physics of a small-scale VAWT using experimental and computational methods. The experiments utilise the University’s low-speed open-section wind tunnel. The design and use of a variety of existing and newly developed methods and apparatus is detailed, this includes the development of an entire VAWT-testing rig and associated measurement equipment. Also included, is a new method for the experimental determination of the power performance. A full performance curve is shown to be determined using a short test taking a few minutes. The near-blade flow physics of the rotating blades were interrogated using particle image velocimetry (PIV) as part of a measurement campaign which goes beyond the existing literature in both the range of measurements taken and the subsequent analysis which is presented. Details of the effect of changes in azimuthal position, tip speed ratio and fixing angle on the flow physics are presented. Comparable CFD simulations are first validated against the PIV measurements before they are used to provide additional information for the performance analysis. A new methodology for determining flowfield-corrected lift and drag polars from a CFD solution allows detailed examination of the performance-impact of the changes in the aerodynamic forces with azimuthal position and tip speed ratio.