Assessment of Vortex Induced Vibrations on wind turbines

The vortex-induced forces on an extruded cylinder with a span of two diameters representative of a finite segment of a non-tapered wind turbine tower at a very high Reynolds number (Re = 8.0×106) are numerically investigated using an incompressible Navier-Stokes flow solver with an Improved Delayed Detached Eddy Simulation (IDDES) turbulence model and correlation-based boundary layer transition modelling. The solution shows spanwise correlated structured vortex shedding with the Strouhal number St = 0.48. The boundary layer transition is found to occur at θ transition = 70 ◦ , and boundary layer separation is found to occur at θ separation = 120 ◦ . Results from the grid dependency study strongly imply that when using IDDES, the Strouhal number converges to higher values than previously reported by the literature as the grid is refined, with results ranging from St ∼ 0.44 using a grid with 4.2 × 106 cells, to St = 0.48 for the finest considered grid with 33 × 106 cells. This behaviour is not seen for URANS, where St = 0.33 for the finest grid.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical investigation of vortex-induced forces on a wind turbine tower segment at very high Reynolds numbers

Ebstrup,

Sørensen,

Bertagnolio

et al. 2024

“…The Reynolds number of the test was 4 2. 6  is the structural critical damping ratio of the vibrating system, y is the deflection of the system in the cross-wind direction and s F is the periodic vortex shedding aerodynamic force. The damping parameter a K of (1) was experimentally obtained through prescribed oscillations of the rigid cylinder model of the form:…”

Section: Brief Description Of the Wind Tunnel Experiments -Aerodynami...mentioning

confidence: 99%

Numerical investigation of vortex induced vibrations on cylinders

Vlastos,

Riziotis,

Papadakis

et al. 2024

The paper addresses Vortex Induced Vibrations (VIV) caused by tower vortex shedding through LES simulations of a wind tunnel experiment. A high-fidelity (HiFi), Fluid Structure Interaction (FSI) framework for aeroelastic analysis of 3D flexible cylinders is established, based on the open-source Computational Fluid Dynamics (CFD) code OpenFOAM and the coupling library preCICE. In the present study, the FSI framework is employed with the aim to replicate a low Reynolds (Re=26000) forced vibrations wind tunnel experiment of a circular cross-section rigid cylinder. The paper compares predictions of the aerodynamic damping of the oscillating cylinder for different oscillation frequencies within the lock-in range and amplitudes against experimental results. While the model consistently predicts the lock-in range of frequencies and the trends in the variation of the aerodynamic damping with the oscillation amplitude, it falls short of accurately capturing the maximum value of the aerodynamic damping at the onset of lock-in.

“…The lack of field and experimental data along with the computational cost of high-fidelity simulations such as Computational Fluid Dynamics (CFD) has led researchers to assess blade VIV using engineering models [2] and CFD simulations of simplified cases such as 2D airfoils [3]. When full-blade CFD simulations have been performed, they have been limited to short time IOP Publishing doi:10.1088/1742-6596/2767/2/022054 2 series and/or reduced parameter space explorations [4,5], far from being sufficient to predict the lock-in range and other characteristics of a full-scale blade subject to VIV under real conditions.…”

Section: Introductionmentioning

confidence: 99%

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

Fernandez-Aldama,

Papadakis,

Lopez-Garcia

et al. 2024

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.