This master thesis covers the principles of wind turbine operation, basic wind turbine classifications, and the significance of airfoils for wind turbines. Geometric and aerodynamic characteristics of airfoils are described, along with the purpose and methods of modifications. 2D CAD models were built for each airfoil profile and corresponding modifications, and meshes of finite volumes were generated in each computational domain. A physical-mathematical model of airflow around the airfoil was established, followed by CFD analysis of airflow around various modified and unmodified airfoils from the NREL S83X series which define the blades of horizontal axis wind turbines. A total of 48 analyses was conducted using the ANSYS Fluent software. The analyses were performed for the NREL S833, S834, and S835 airfoil profiles, along with their modifications of 5°, 10°, and 15° under angles of attacks ranging from 0° to 15°. Results indicate an increase in lift and drag coefficients with increasing angles of attack, while the application of modifications decreases both coefficients. Despite reductions in lift and drag coefficients, specific modifications under higher angles of attack suggest improved aerodynamic efficiency, especially for S833 and S835 at angles of 10° and 15°. Modifications have the potential to eliminate vortex trails, which can enhance turbine performance, reduce blade stresses, and expand the operational range of wind turbines. Obtained results of lift, drag, and aerodynamic efficiency coefficients are presented in tables and graphs. In addition to tabular and graphical representations, the thesis includes visual comparisons of airflow around modified and unmodified airfoils at various angles of attack.