Numerical study of the effect of flap geometry in a multi-slot ducted wind turbine

Abstract

One possible way to harness wind more efficiently in low-wind urban areas is to place wind turbines inside a duct. A known issue of such approach is due to the flow separation that can occur at the diffuser walls. This can be avoided using a channelled structure consisting of a duct and a flap, also known as a multi-slot system. The present work describes the effects of a flap geometry on the turbine performance, through computational fluid dynamics (CFD). Four flaps based on airfoils, with different thicknesses and cambers, were evaluated. It was found that thinner and more cambered flaps produce higher wind turbine performance, showing power augmentations up to 2.5 compared to a bare turbine. A comparison between the multi-slot design and a single-piece duct of the same geometry was also performed, showing that the multi-slot design is more efficient if the flow is maintained attached to the flap.