## 4 Conclusions  
In this study, a CFD-based in-depth investigation was conducted to determine the effects of the shape of the VG and the layout of VGs on the power performance of a wind turbine. The RSM was used to investigate the influence of VG design variables, and complex simulations using more than 55 million elements were carried out. Based on the in-depth investigation, the following conclusions were drawn. 1. A CFD analysis of multi-MW wind turbine blades was performed, and subsequently validated by comparing the results with those obtained with the GH Bladed design values. Figure 19: Separation line and surface streamline of blade (**a**) without VG and (**b**) with VGs. Figure 18: Surface streamline of wind turbine blade (**a**) without and (**b**) with the VGs. 2. The influence of the VG design parameters was investigated using CFD analysis, which confirmed that the VG reduced the occurrence of separation flow, increased the lift, and reduced the drag at high angles of attack. 3. Analysis of the flow characteristics of the blade with the mounted VGs confirmed that the tip vortex generated by the VG reduced the separation area by allowing the high-energy fluid to flow to the low-energy separation area. 4. The VGs were confirmed to play an important role by improving the aerodynamics of multi-MW wind turbines by 2.80% at the rated wind speed. This was confirmed by the simulation at the rated wind speed with more than 55 million elements. 5. The results of this study are expected to be useful for selecting the mounting position and shape of the VG by conducting a full-scale simulation by automating the construction of the simulation environment. The selected VG discussed in this study is currently installed in a 2.3 MW wind turbine and is being monitored using SCADA systems. The VG could also be installed on other large wind turbines by using the proposed method for constructing a computational environment. Conceptualization, [PERSON]-H.J. and K.H. ; methodology, J.-H.J. ; software, H.-G.M. ; validation, [PERSON]-H.J. and H.-G.M. ; formal analysis, [PERSON]-H.J. and H.-G.M. ; investigation, [PERSON]-G.M. and [PERSON]-H.J. ; resources, S.P. ; data curation, S.P. ; writing--original draft preparation, [PERSON]-G.M. ; writing--review and editing, [PERSON]-G.M. ; visualization, [PERSON]-G.M. ; supervision, [PERSON]-[PERSON] and K.H. ; project administration, [PERSON]-H.J. ; funding acquisition, [PERSON]-H.J. All authors have read and agreed to the published version of the manuscript. This work was supported by Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government (MOTIE) (20203020020030, Feasibility Study of 20 MW Super-Capacity Wind Turbine Generator System Development). Not applicable. * [PERSON] et al. (2011) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON] 3-Dimensional Flow Field Analysis and Tip Shape Design in a 2.5 MW Wind Turbine Blade. In Proceedings of the Korea Wind Energy Association, Spring Conference, Daegu, Korea, 7-8 April 2011; pp. 51-56. * [PERSON] et al. (2011) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]-W. 3-Dimensional Flow Field Analysis and Tip Shape Design in a Wind Turbine Blade. In Proceedings of the Korean Society for Computational Fluids Engineering, Spring Conference, Jeju, Korea, 26 May 2011; pp. 243-248. * [PERSON] et al. (2008) [PERSON]; [PERSON]; [PERSON]; [PERSON] Evaluation of the performance of vortex generators on the DU 91-W2-250 profile using stereoscopic PIV. In Proceedings of the 12 th World Multi-Conference on Systemics, Cybernetics and Informatics (WMSCI 2008), Orlando, FL, USA, 29 June-2 July 2007; pp. 263-267. * [PERSON] et al. (2006) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON] Aerodynamically shaped vortex generators. _Wind Energy_**2016**, _19_, 563-567. [CrossRef]
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