In this research, three-dimensional Computational Fluid Dynamics Models were developed to simulate flow around a two-bladed rotor with and without yaw effects. The NREL Phase VI two-blade rotor is used. Finite volume-based commercial software ANSYS/FLUENT was applied in the simulation, and turbulence flow around the rotor blade was simulated by the LES model. The numerical models were first validated by comparing simulation results with experimental data for cases without yaw effects. Detailed results including wake flow structure, torque, thrust, power, and power coefficient were obtained and analyzed. Then numerical investigation of NREL Phase VI rotor with yaw effects was conducted. Simulation results including flow around wind turbines, power output with and without yaw effects are analyzed. At the end, a triangle relationship between turbine power output, upstream wind speed, and yaw angle was obtained. Results from this research are expected to provide a better understanding of aerodynamic features for flow around wind turbines, which can be expected to contribute the optimal design and operation of Horizontal Axis Wind Turbines and eventually effectively harness wind energy.