Estimation of extreme loads on a wind turbine blade at large angle-attack and high velocity

Abstract

Angle-of-attack (AoA) of wings, blades and other geometric shapes has a dominant role in the generation of aerodynamic forces and turbine power since it changes the flow behavior. The development of software and computers has enabled simplified numerical testing, which reduces time while saving resources compared to experimental testing. Computational fluid dynamics (CFD) is a strong numerical tool that is being increasingly utilized to simulate a wide range of flow processes across many industries and is much employed in engineering design. One of the most common approaches is to use Reynolds-averaged Navier-Stokes (RANS) family of turbulence models where all effects of turbulence are modeled. For near-wall treatment, in aeronautics, the k-ω shear stress transport (SST) model is widely employed. In this paper, small horizontal axis wind turbine (model DE-AW01) blade at different AoAs has been numerically investigated. A detailed description of the blade geometry is also given. Numerical simulations of full three-dimensional flow fields using the k-ω SST turbulence model for the closure of the governing flow equations have been performed. The tests were performed at a high wind speed of 35 m/s (126 km/h) at AoAs of 85, 90 and 95 degrees which corresponds to extreme weather conditions. It has been confirmed that numerical simulations can provide sufficiently accurate estimates of the axial force and power. Furthermore, the obtained results were compared, primarily lift and drag, as the two most dominant components of aerodynamic forces, and the most convenient flow case, that minimizes blade loading, has been determined.