Description
A three-dimensional numerical method was used to validate the aerodynamic performance of a two-bladed wind turbine. The method is based on ideal fluid mechanics (e.g., potential flow) and the simpler governing equations require only a few minutes of computational time. The spiral wake is modeled as a vortex sheet, providing the induced velocity effects without vortex decay, a problem inherent to some other numerical methods. Also, for an efficient wind turbine design, flow-separation on the blades must be avoided. Therefore, for such attached flow problems, the current inviscid-flow model is not only faster but provides satisfactory results. Calculated torque, axial force, and efficiency values compared well with similar data published by NREL (National Research Energy Laboratory) for a two-bladed wind turbine. Blade-section pressure coefficients were also calculated and presented for this baseline design and areas where flow separation is possible were identified. Based on these observations, a modified airfoil section was proposed, using the same blade planform geometry. Computed results and comparisons with the baseline wind turbine geometry indicate that improvements in both power and efficiency are possible (in spite of the baseline being very well designed). The method presented here paves the way for a more comprehensive redesign modification where both blade shape, twist and airfoil section can be improved. This approach can enhance performance over a wider range of wind turbine geometry and wind speed conditions.
