The aim of this project is to investigate the aerodynamic performances of airfoil, especially NACA 4415, using the method of Computational Fluid Dynamics. The NACA 4415 was modeled and meshed in ICEM and then was simulated by using transition SST (shear stress transport) 4-equation model in ANSYS Fluent 15.0 with different Reynolds number and various angles of attack. Lift, drag, pressure distribution and wall shear stress were highly focused during post-processing. The computational results were compared with Xfoil and experimental data collected by The Ohio State University (OSU) in 1996. User Defined Functions (UDF) were also tested during the calculations in order to find the most optimal results. In addition to the isolated airfoil, this project also investigated the cascade effect of blade elements with a NACA 4415 airfoil profile with different solidities (ranges from 0.05 to 0.4). While the typical range for a 3-blade horizontal wind turbine is from 0.021 to 0.11 [1]. Aerodynamics of the airfoil will be influenced by different solidities.