Original Article A triangular vortex generator modeling on a DU97-W-300 airfoil by a source term model L Galera 1 , P Martinez-Filgueira 1 , U Ferna ´ ndez-Ga ´miz 1 , E Zulueta 2 , JM Lopez 2 and JM Blanco 1 Abstract Vortex generators are passive devices employed to improve the aerodynamic performance of aircraft and wind turbine blades. More concretely, these devices have high potential in improving the power output of wind turbines that are producing less power than expected. Besides, it can improve the aerodynamic performance of the nearest parts to the rotor of turbine blades that usually enter in stall. The main goal of this article is to model the triangular vortex generator effect on a DU97-W-300 airfoil by a source term model. This is aimed by comparing the lift and drag coefficients from experimental studies with the data obtained in the computational fluid dynamics study. Furthermore, the vertical path and the size and strength of the vortex are studied for different angles of attack in order to see how the vortex genertaor behaves in different conditions. Keywords Vortex generators, source term model, wind turbine, flow control Date received: 24 September 2018; accepted: 18 April 2019 Introduction Wind energy has risen as one of the most important energy sources since 1960s. 1 Nowadays in the United States, wind energy is the renewable energy with the largest overall installed capacity. 2 Its importance is also reflected in the constant rise of the total capacity installed in Europe for the last 15 years. 3 However, this increase can only be achieved nowadays by making turbines with a bigger rotor area or creating bigger wind farms. The increase in the size of the blades calls for the design of thicker airfoils that are installed in the areas near the hub, as explained by Gao et al., 4 in order to enhance the blade structure but are found to have poor aerodynamic perform- ance. 5 These types of airfoils can have a thickness of up to 40% of chord of the airfoil. 6 Due to this thick- ness it is normal that the flow separates in these air- foils. One of this type of airfoil is the DU97-W-300 airfoil developed by Timmer et al. 7,8 and used in real wind turbines such as the 5 MW turbine for the off- shore system developed by the National Renewable Energy Laboratory (NREL) of the United States. 9 Nonetheless, one of the technologies that can improve the aerodynamic performance of currently installed wind turbines 6,10 and, more concretely, of these types of airfoils, are the vortex generators (VGs). VGs are a passive control system that projects perpen- dicular to the surface by increasing the near-wall momentum through its transfer from the outer flow to the wall region or inner flow. 11 However, this tech- nology is not only applied to wind turbines but also to gas turbines as mentioned by Satta et al., 12 thus show- ing that these devices are highly effective. VGs were firstly introduced by Taylor in the early 1940s. 11,13,14 These passive devices had a height that was between 80% and 100% of the boundary layer thickness. The transport momentum was achieved by the production of streamwise vortices behind the VGs. 15 Usually these devices are used to delay the boundary layer separation, 16 which occurs near the maximum loading point, 17 and to increase the 1 Department of Nuclear and Fluid Mechanics, University of the Basque Country (UPV/EHU), Vitoria-Gasteiz, Spain 2 System Engineering and Automation Control Department, University of the Basque Country (UPV/EHU), Nieves Cano, Spain Corresponding author: U Ferna ´ndez-Ga ´miz, Department of Nuclear and Fluid Mechanics, University of the Basque Country (UPV/EHU), Nieves Cano, 12, 01006 Vitoria-Gasteiz, Spain. Email: unai.fernandez@ehu.es Proc IMechE Part A: J Power and Energy 0(0) 1–11 ! IMechE 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0957650919850449 journals.sagepub.com/home/pia