In the present study, the 3D flow around the rotating wind turbine whose blade’s geometry is tapered and twisted is observed by using Computational Fluid Dynamics (CFD) as a numerical simulation tool. The CFD simulation of the wind turbines is essential for their efficient use and optimization of the solutions. This paper shows the accuracy of numerical simulation of Reynolds Averaged Navier Stokes equations (RANS equations) along with the Shear Stress transport k-ω turbulence model and validation with the experimental data by the National Renewable Energy Laboratory. All the simulations in this paper are performed on the sequence S of the test configuration of the experiment conducted at the NASA Ames Wind tunnel facility with the blades rotating at constant RPM and varying inlet wind speeds. The results of this study depict a close agreement with the experimental data. The torque predicted by this method is well in line with the experimental values, and it is also able to predict the stalling regions of the wind turbine. This study captures the pre-stall, stall & deep-stall regions and also the 3-dimensional flow around the wind turbine. The flow separation starts occurring on the wind turbine when the inlet speed is greater than 10 m/s, and it is observed that the turbine goes into the deeps stall region when the wind speed is 18m/s.