Wind energy plays a critical role as a safe and clean source of energy. However, the complexity of wind patterns produced by the topographical characteristics of urban environments considerably affect the performance of urban wind turbines. In order to address these effects, this study utilizes both Computational Fluid Dynamics (CFD) and meteorological data in order to simulate the wind flow in an urban area and to predict the performance of a wind turbine at specific locations on top of buildings. This thesis presents a review of vertical axis wind turbines and the desirable locations of these types of wind turbines above a building in an urban area. Numerical simulations offer a cost-effective method with an acceptable accuracy to evaluate wind turbine locations. Two test cases have been studied to illustrate the behavior of wind turbines located on the roofs of buildings. The full scale of the urban area and the computational domain are constructed, and the flow is simulated based on the STAR CCM+ ® software. The three-dimensional, steady Reynolds-Averaged Navier-Stokes equations are solved to obtain the velocity of the wind in urban areas. Meteorological data is then used to estimate the potential energy production at specific locations on the top of a building. Multiple locations are studied in terms of annual total Energy output to find out the best potential position for turbine installation. Results demonstrate a significant difference of energy output for different locations of the wind turbines on the same building. This study introduces an effective tool to study the annual total energy output potential at multiple locations above the building in much shorter time span (within a month) rather than the existing experimental or field methods.