Numerical study of noise emission for a vertical axis wind turbine
Abstract
This project aims to study noise emission from vertical axis wind turbines (VAWTs). Reducing the noise produced by wind turbines is a key environmental factor which is very important for the acceptance of the technology. The VAWTs are popular to install in residential/urban areas, which makes sound emissions especially important. As the VAWT blades typically move at a slower speed, than the corresponding horizontal axis turbine, there is a possibility for significantly reducing the sound emissions. However, as the VAWTs spin around the vertical axis, the incoming flow interacts with the wake created by the shaft and blades rotating upwind. This interaction generates high turbulence, which is an additional source of sound emissions. The result is that the VAWT has the potential for low sound emissions, but to fully utilize this potential, the mechanism of how the noise is generated requires further understanding.
The final goal of this project is to find a solution for reducing the sound emission. Uppsala University owns a 200 kW VAWT, which is built at the west coast of Sweden. Previously our research group have measured the sound from the turbine to localize the aerodynamic noise sources. The results indicated that the noise is emitted especially from the joints between the blades and its supporters. Our numerical method will help to identify the location of sound sources and to make clear under which conditions and to what extent the noise occurs. The numerical results will be compared with experimental data to validate accuracy of our model.
