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.

Velocity Augmentation Model for an Empty Concentrator-Diffuser-Augmented Wind Turbine and Optimisation of Geometrical Parameters Using Surface Response Methodology

“…Notably, it is suitable for adverse pressure gradients, insensitive to free-stream turbulence in the far wake region, and eliminates the need for damping functions [72]. The model choice was based on extensive literature recommendations for aerodynamic purposes, especially in shrouded wind turbines [9,11,12,37,40,42,[67][68][69][72][73][74][75][76][77][78].…”

CFD-Based J-Shaped Blade Design Improvement for Vertical Axis Wind Turbines

“…For such devices, the rotor is surrounded by a duct, to increase the mass of air inside the turbine, and, thus, the power output [6]. Recent studies on DAWT have covered the analysis of ducts with several design variations, including the addition of a brim [7] or a flap [8].…”