Numerical evaluation of aerodynamic loads and performances of vertical-axis wind turbine rotor

Abstract

Three-dimensional, unsteady, turbulent, incompressible flow simulations of isolated vertical-axis wind turbine (VAWT) high-solidity rotor consisting of three straight blades at seven different operational regimes have been performed in ANSYS FLUENT by finite volume method. Aerodynamic analysis of this type of wind turbine rotors is interesting and extremely complex because the blades pass through a wide range of angles-of-attack during one revolution, and many flow instabilities as well as flow separation occur. Furthermore, the simulation of high-solidity rotors is even more difficult, due to the significant interference between the blades, or more precisely, between the wake of the advancing blade and the retracting blade. The rotational motion of the blades is solved by the unsteady Sliding Mesh (SM) approach. Flow field is modeled by Unsteady Reynolds Averaged Navier-Stokes (URANS) equations with k-ω SST turbulence model and hybrid Scale-Adaptive Simulation (SAS) used for closure. Quantitative and qualitative examinations of the obtained numerical results are done by comparison to the available wind tunnel data. In particular, aerodynamic loads acting on a blade per revolution as well as power coefficient curves are investigated in detail and comparisons between the two turbulence models are made. Final distinguishing between the simpler and more complex approach to turbulence modeling is made by visualizations of turbulent flow structures separating from the blades throughout a cycle at both non-optimal (starting) and optimal working regimes.