An efficient 3D CFD model for the analysis of the flow field around Darrieus rotors

An efficient numerical technique has been developed in order to investigate flow characteristics and global performance of Darrieus rotors. The interest for this kind of vertical axis wind turbines arises from their great capacity for integration within urban areas and for distributed generation. The proposed methodology is based on the solution of the steady three-dimensional governing equations, by means of a robust commercial CFD code. Since the effect of the turbine blades on the flow field is simulated through the introduction of momentum sources in the porous shell representing the volume swept by the turbine blades, any expensive refinement of the grid, near the rotor, is avoided. This approach dramatically reduces the computational costs, with respect to conventional unsteady flow simulations. The model efficiency enables the simulation of the flow field around Darrieus rotors considering complex and realistic computational domains, for instance when these turbines are clustered within a wind farm or placed inside urban areas. The methodology is validated by reproducing the performance of the Sandia 17-meter Darrieus rotor with approximate troposkien shape. Comparisons with other codes are also presented in order to highlight the advantages of the proposed method.