Pseudo three-dimensional numerical investigation of legacy vertical axis wind turbine configurations

Abstract

In this paper, a pseudo three-dimensional computational fluid dynamics model of Sandia’s 17-meter Vertical Axis Wind Turbine is implemented and validated against experimental data for a Tip Speed Ratio of 4.60. The Unsteady Reynolds Averaged Navier Stokes equations and the Shear Stress Transport turbulence model are used to assess the performance of the turbine in conjunction with ANSYS CFX’s rotating domain setup. The pressure coefficient, normal coefficient and tangential coefficient were used as validation metrics. The numerical results showed good agreement with the experimental data, with the normal force coefficient differing from the experimental data by 32% on average, and the tangential force coefficient differing by 51%. Discrepancies between the numerical and experimental data are likely associated with two sources: 1) the assumption of a fully turbulent boundary layer resulting in an over-prediction of drag; 2) the inherent deficiencies associated with two-equation turbulence models such as the stagnation point anomaly as well as the dissipative nature of Reynolds Averaged Navier Stokes based turbulence models. The model was also able to predict the asymmetric power generation associated with vertical axis wind turbines due to the blade-wake interaction during the downwind revolution.

Keywords

• Vertical axis wind turbine (VAWT)
• Computational Fluid Dynamics (CFD)
• Aerodynamics
• URANS
• Shear Stress Transport turbulence model