Characterization of vortex-shedding regimes and lock-in response of a wind turbine airfoil with two high-fidelity simulation approaches

Abstract

In this work, the vortex-induced vibration (VIV) phenomenon affecting a wind turbine airfoil section at 90° incidence is analysed with two numerical approaches, a two-dimensional (2D) setup of the airfoil, simulated using the unsteady Reynolds-averaged Navier-Stokes equations, and a three-dimensional (3D) setup with a span-to-chord aspect ratio of 1, employing the delayed detached-eddy simulation model. A constant inflow velocity is considered for a Reynolds number around 2×106. The only structural degree of freedom is the airfoil chordwise displacement. As a reference, simulations of the static airfoil are also performed. By running the 3D static simulation for a sufficiently long time, the vortex shedding is found to have intermittent periods of different characteristics, including different Strouhal numbers. The VIV simulations are performed at different inflow velocities to cover the lock-in range, and a new robust metric is proposed to characterize this range. This robust characterization and the insight gained about the multiplicity of Strouhal numbers have allowed the present authors to make a fairer comparison between the 2D and 3D simulation results than in previous works. The outcome of this comparison is that, inside the lock-in range, the 2D and 3D approaches predict a very similar VIV development.