Numerical modeling of the flow over wind turbine airfoils by means of Spalart–Allmaras local correlation based transition model

• Published in: Energy (Oxford) 2017-07, Vol.130, p.402-419
• Main Authors: D'Alessandro, Valerio, Montelpare, Sergio, Ricci, Renato, Zoppi, Andrea
• Format: Article
• Language: English
• Subjects: Aerodynamic coefficients; Aerodynamics; Computational fluid dynamics; Computer applications; Computing costs; Computing time; Fluid dynamics; Fluid flow; Hydrodynamics; Laminar flow; Navier-Stokes equations; OpenFOAM; Reynolds averaged Navier-Stokes method; Robustness (mathematics); Software; Spalart-Allmaras turbulence model; Spalart–Allmaras model; Stokes law (fluid mechanics); Studies; Transition modeling; Turbines; Turbulence; Turbulent flow; Wind power; Wind tunnel testing; Wind turbine airfoils; Wind turbines
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2017.04.134

The aerodynamics of the blade sections constitute the core problem in the design of new-generation wind turbines. Aerodynamic theories for blade design suffer from the unavailability of aerodynamic coefficients for the airfoils involved in the blade. The aim of this work was therefore to develop an efficient and accurate tool for computing the flow parameters, reducing the need for complex and costly wind tunnel tests. Our approach is based on Computational Fluid Dynamics (CFD) and consists in the adoption of a laminar-to-turbulent transition model. For the flow regimes involved in wind energy applications, the fully turbulent or laminar flow model fails completely in the prediction of aerodynamic performance. We consequently propose a Reynolds Averaged Navier Stokes (RANS)-based approach capable of modeling transitional flows with a limited computational cost. This is a crucial aspect because standard RANS models assume a fully turbulent regime. Our proposed approach couples the well-known γ−Reθ,t˜ technique with the Spalart-Allmaras turbulence model. The effectiveness, efficiency and robustness of the computational method introduced here were tested by computing the flow over several wind turbine airfoils. •A Spalart–Allmaras local correlation transition model implementation was proposed.•Several wind turbine airfoils at different flow regimes were studied.•Transition modeling turned out to be essential to accurately study wind turbine airfoils.