## 4 Conclusions  
In the present study, the primary vortex generated by a single vane-type vortex generator (VG) has been characterized. Numerical simulations were carried out using open-source OpenFOAM code for four incident angles, \(\beta=10^{\circ}\), \(15^{\circ}\), \(18^{\circ}\), and \(20^{\circ}\) and six VG heights, 0.2H, 0.4H, 0.6H, 0.8H, H, and 1.2H, where H  
Figure 9: Peak vorticity and circulation for different VG sizes at a \(5\delta\) distance from the VGs trailing edge. (**a**) Streamwise peak vorticity; (**b**) ositive circulation. is the value of the BL thickness \(\delta\) at the VG position. The vortexes generated by these VGs were simulated considering turbulent, steady, state and incompressible flow with a Reynolds number of \(Re=\) 27,000 based on the local BL thickness \(\delta\) at the VG position. The parameter used to measure the vortex size was the half-life radius \(R_{0.5}\), and the results showed that this value is significantly dependent on the VG height and vane incident angle. In general, the higher the VG height, the larger the size of the primary vortex. For the lowest incident angle \(\beta=10^{\circ}\) studied, the largest size of the vortex is achieved by the highest VG case of 1.2H. However, as the incident angle increases, the differences in the size of the vortex in comparison with smaller vanes are not relevant. As expected, the vortex trajectory is affected by the VG height, as well as by the incident angle \(\beta\), and this path variation is more evident for the larger angles. In each simulated case, the vertical trajectory of the vortex is almost constant, with the exception of the 0.2H VG height case. This behavior may be due to the low VG height, which is within viscous sublayer where viscous effects are dominant and, therefore, an interaction with the wall appears. Regarding the wall shear stress, two conclusions can be drawn. Firstly, a variation of the wall shear stress with the incident angle was confirmed. Larger wall shear stress values were obtained for higher incident angles \(\beta=18^{\circ}\) and \(20^{\circ}\), and these values decrease along the streamwise direction. Secondly, the VG sizes 0.4H and 0.6H at the incident angle of \(\beta=20^{\circ}\) reached the largest wall shear stress along the streamwise direction. Additionally, the circulation shows the highest values are for 0.4H and 0.6H VG heights and \(\beta=18^{\circ}\) and \(20^{\circ}\) at \(5\delta\) distance from the TE, results that agree with the obtained wall shear stress conclusions. Therefore, those vane heights and incident angles seem to be the best option for flow separation control. CFD techniques are the most commonly methods used to improve the optimization of VGs on wind turbine blades, so the results and information presented by this study can be used as a model and guidance for effective implementation of VGs. Due to the high variety of parameters that have influence in the problem, such as VG height and orientation, a precise understanding of the flow gains importance for successful application of VGs. A further step would be the simulation of different VG sizes and orientation in typically used airfoils for wind turbine blades at different Reynolds numbers. I.I.-U., I.E., U.F.-G., and E.Z. performed the numerical simulations and carried out the post-processing. [PERSON] supervised the manuscript. This research was partially funded by the Government of the Basque Country through the ELKARTEK program and by the Fundation VITAL Fundazioa. The authors are grateful to the University of the Basque Country UPV/EHU through the EHU 12/26 research program. The authors declare no conflict of interest. The following abbreviations are used in this manuscript:  
V.V. Figure 12: Axial velocity distributions \(\mathrm{U}\mathrm{x}\mathrm{m}^{-1}\) at four different planes normal to the streamwise direction and located at distances proportional to the local boundary layer thickness \(\delta\) from the edge shown for six vortex generator heights (0.2H, 0.4H, 0.6H, 0.8H, H and 1.2H).