## 1 Introduction  
In the last few decades, several flow control devices have been developed, and some of them were installed onto wings in order to improve aerodynamic efficiency. At present, this type of elements is being optimized by researchers to be introduced in wind turbines. A four-layer scheme was developed by [PERSON] [1] for the classification of the different types of flow control devices. [PERSON] classified the control devices as active or passive, geometric or fluidic, steady or unsteady, and attached or separated devices. Flow control devices can be categorized as active or passive; this classification depends on their operating principle, see [PERSON] et al. [2; 3] and [PERSON] et al. [4]. Passive control techniques would represent an improvement in turbine efficiency and load reduction without external energy consumption. In contrast to passive devices as VGs, more complex algorithms are needed to get efficiency advantages by active control methods, see [PERSON] et al. (2019). A further study and discussion of fifteen different flow control devices for wind turbines was made by [PERSON] et al. (2019). Vortex generators (VG) are passive flow control devices that modify the boundary layer progress, taking momentum transfer between higher layers or free stream velocity and introducing it into the inner flow region nearer from the wall. The aim of VGs is to delay or in extreme cases avoid the separation of the boundary layer increasing the lift coefficient, see [PERSON] (2017). However, VG installations can produce a drag increase, a clear disadvantage for flow control devices. When the closest part to the wall or leading edge of a blade reverts the flow direction, then the boundary layer detachment begins. Due to the design of the VGs, a momentum transference is made between the free stream velocity and the fluid near the wall, signifying that the boundary layer gets re-energized and the detachment delayed ([PERSON] et al., 2019). After this energy transference, the boundary layer thickness gets reduced, while the velocity of the inner region of the boundary layer (BL) grows; therefore, the detachment of the flow is delayed ([PERSON] et al., 2019). Moreover, a drag reduction and lift increasing was observed caused by sub boundary layer VGs, see [PERSON] et al. (2019). The main purpose of installing VGs on wind turbine blades is to delay or avoid the flow detachment and to decrease the effect of the roughness on the blade. VGs are typically installed in spanwise raws on the suction side of the blade; the principal advantage shown by VGs is that they can be attached as a post-production fix in blades that do not work as expected. Therefore, VG installations suppose a simple alternative to improve the rotor performance ([PERSON] et al., 2019). Thus, it is important to control and optimize parameters such as the vortex trajectory and vortex core size of VG-generated vortexes, see [PERSON] et al. (2019). In order to improve the location in the spanwise direction of VGs and the design of a wind turbine blade, computational fluid dynamics (CFD) techniques can be an interesting as shown in [PERSON] et al. (2019). Basic research on VGs as flow control devices on square cylinder was made by [PERSON] et al. (2019) and [PERSON] (2019), with successful results in flow separation control. The streamwise vortexes generated by a rectangular VG in a flat plate and negligible streamwise pressure gradient flow were investigated by [PERSON] et al. (2019) and [PERSON] et al. (2019) in order to conclude the possibility of an accurate reproduction by CFD simulations of the characteristics of the wake behind VGs. For example, in the study carried out by [PERSON] et al. (2019) on a DU97-W-300 airfoil, a significant increase of the maximum lift coefficient was observed due to the installation of VGs. Higher lift and drag coefficients values were observed than the ones obtained in steady state conditions as the incident angle increases. Stereoscopic particle image velocimetry measurements carried out by [PERSON] et al.