3D Numerical Study Of Hill Mounted VAWT

The ground topography effect on the wind flow is significant. The knowledge of the flow behavior near ground is crucial in the development of wind power, especially in the choice of suitable sites and for estimation of energy production. In this paper, the numerical prediction of the flow over a three-dimensional hill model and the analysis of placement of Savonius turbines on top of the hill are presented. The numerical analysis is based on the finite volume method implemented in the ANSYS CFX 15 Software using the Shear-Stress Transport (SST) turbulence model. The numerical results for a conventional Savonius rotor and a vertical-axis spiral wind rotor are both satisfactory compared with experimental data. The performances of these turbines, installed on the hilltop, are studied for different height positions. Furthermore, the influence of the hill size on the extracted power is investigated. At TSR=1, the power coefficient of a conventional rotor is increased from 0.15 to 0.32 when the rotor is installed at a height of 0.25 m above the top of the hill, while it reaches 0.40 when the hill is two to three times higher. The helical Savonius rotor tested gives even higher power coefficient of 0.44.