Two-dimensional numerical simulations of vortex-induced vibrations for wind turbine towers


Vortex-induced vibrations (VIV) of wind turbine towers can be critical during the installation phase, when the rotor-nacelle assembly is not yet mounted on the tower. The present work uses numerical simulations to study VIV of a two-dimensional cylinder under conditions that are representative of wind turbine towers, both from a fluid-dynamics and structural-dynamics perspective. First, the numerical tools and fluid-structure interaction algorithm are verified by considering a cylinder vibrating freely in a laminar flow. In that case, both the motion amplitude and frequency are shown to agree well with previous results from the literature. Second, VIV is modelled in the turbulent supercritical regime using Unsteady Reynolds-Averaged Navier–Stokes equations. In this context, the turbulence model is first validated on flow past a stationary cylinder at high Reynolds number. Then, results from forced vibrations are validated against experimental results for a range of reduced frequencies and velocities. It is shown that the behaviour of the aerodynamic damping changes with the frequency ratio, and can therefore lead to either self-limiting or self-exciting VIV when the cylinder is left to freely vibrate. Finally, results are shown for a freely-vibrating cylinder under realistic flow and structural conditions. While a clear lock-in map is identified and shows good agreement with published numerical and experimental data, the work also highlights the unsteady nature of the aerodynamic forces and motion under certain operating conditions.

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