High-fidelity simulations of airfoil vortex-induced vibrations: from 2D to blade-like aspect ratios

Abstract

Large edgewise vibrations due to vortex shedding can be suffered by a wind turbine blade when the rotor is stopped or idling and there is massively separated flow. High-fidelity simulations of these vortex-induced vibrations (VIV) with a full-blade model are very computationally expensive, and so currently reported results of this type are limited to short time series or reduced parameter spaces, far from being sufficient to predict the lock-in range and other characteristics of a full-scale blade response to VIV under real conditions. This computational cost has led researchers to, alternatively, study VIV using simplified approaches, like simulations of 2D and short-span airfoil sections. To help bridge the gap between expensive full-blade and short-span airfoil section simulations, in this work the VIV response of an airfoil section is obtained for three different aspect ratios —from 2D to a blade-like aspect ratio—, using CFD simulations coupled with a one-degree-of-freedom structural oscillator model. The results obtained show that inside the lock-in range the airfoil’s initial VIV response is very similar for all aspect ratios studied, despite notable differences in the Strouhal number obtained. In contrast, outside lock-in the aerodynamic forces vary substantially from one case to another.