MSc forsvar ved Thawatchai Wanthanadamkerng

Supervisor: Niels N. Sørensen, DTU Vindenergi

Co-Supervisor: Niels Troldborg, DTU Vindenergi

Abstract: CFD modelling of an airfoil section equipped with Vortex generators

The use of vortex generators (VGs) is a prevailing technology in large modern wind turbines due to its potential to increase wind turbine annual energy production [39] by re-energizing the momentum energy in the boundary layer and, as a consequence, delay the flow separation. Many researchers have been extensively studying the effects of VGs on airfoil sections but none have included the VGs’ baseplate into their studies. This research aims to fill this gap and hopes to contribute toward the current body of work in VG research by studying the effect of the baseplate on the airfoil aerodynamics.

The main goal of this thesis is to identify the effect of the baseplate of the vortex generators. The effect of VG positions, VGs with baseplate, Reynolds number, baseplate height and roughness model were studied in order to achieve the goal. Five baseplate shapes were studied in this research in order to cover all possible geometries in the real applications. Airfoil section with VGs were shown to be effective in delaying flow separation for both FFA W3-301 and DU 91 W2-250 airfoils. From the results of the simulations of airfoil sections with baseplate and VGs, baseplate shape no.2 (sharp bevel) shows an early flow separation and has the worst performance. The baseplate shape no.5 (”S” shaped bevel) shows results that were close to the airfoil without baseplate.
In studying the airfoils with roughness, it was seen that by adding VGs, the loss in lift was restored. A reference wind turbine model was used in order to compute the wind turbine’s annual energy production. The rough airfoil had an annual energy production approximately 18% less than the clean airfoil for FFA W3-301 and approximately 13% for DU 91-W2-250. By adding VGs to the rough airfoil section, the AEP increased by around 10% for FFA W3-301 airfoil with VGs at 0.20c and approximately 5% for DU 91-W2-250 airfoil with VGs at 0.20c. Taking the baseplate (except baseplate shape no.2) into consideration, both the maximum lift and aerodynamic efficiency saw slight improvements in both airfoils. This could be a consequence of the baseplate which allowed the flow to pass resulting in accelerating flow being able to be energized by the VGs.

From the studies, the baseplate shape no.2 (sharp bevel) had performed poorly in simulations with both airfoils, although the flow separation was seen to be delayed at high Reynolds numbers. However, due to the simplicity in manufacturing, this shape may still be used in practice and as such, it is highly recommended that the baseplate configuration is taken into accounted during the design process. This research has shown that it is advantageous to have baseplates with a smooth bevel likes baseplate shape no.1 (beveled edge) and 5 (”S” shaped bevel) in order to avoid unexpected flow separation. The effect of the baseplate could also be more important to account for in simulations as the height of the baseplate might increase in the future, if a larger VG is needed.

 

Tidspunkt

ons 23 aug 17
13:00 - 15:00

Arrangør

DTU Vindenergi

Hvor

Technical University of Denmark
DTU Risø Campus, Building 100.
Frederiksborgvej 399, 4000 Roskilde