Vortex induced vibrations of wind turbine blades: Influence of the tip geometry

Horcas, Sergio González; Barlas, Thanasis K.; Zahle, Frederik; Sørensen, Niels N.

doi:10.1063/5.0004005

Cited by 45 publications

(55 citation statements)

References 83 publications

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“…The tested tip shape in this work is a scaled version of that aeroelastic tip prototype (publication pending). The optimization method used is the same as the one described in Barlas et al (2020), used for the tip design of a full-scale wind turbine. The method of optimizing the tip for the RTR is essentially the same, while the baseline geometry and load envelope is defined by a reference straight tip, designed for an optimal BEM performance.…”

Section: Tip Model Designmentioning

confidence: 99%

“…Traditional-aircraft-related bibliography (e.g., see Hoerner and Borst, 1975) covers most of the aerodynamic aspects of winglets and swept wing tip shapes, but the specific design space and objectives of wind turbine applications require distinct research efforts even considering non-rotating setups, as in this work. Existing research work relevant to wind turbine applications typically focuses on winglets and aerodynamic tip shapes, with limited testing in controlled conditions (Johansen and Sørensen, 2006;Gaunaa and Johansen, 2007;Gertz et al, 2012;Hansen and Mühle, 2018). Moreover, there is no relevant research work focusing on details of tip shape aerodynamics relevant to the application of tip extensions for blade upscaling.…”

Section: Introductionmentioning

confidence: 99%

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Wind tunnel testing of a swept tip shape and comparison with multi-fidelity aerodynamic simulations

et al. 2021

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Abstract. One promising design solution for increasing the efficiency of modern horizontal axis wind turbines is the installation of curved tip extensions. However, introducing such complex geometries may move traditional aerodynamic models based on blade element momentum (BEM) theory out of their range of applicability. This motivated the present work, where a swept tip shape is investigated by means of both experimental and numerical tests. The latter group accounted for a wide variety of aerodynamic models, allowing us to highlight the capabilities and limitations of each of them in a relative manner. The considered swept tip shape is the result of a design optimization, focusing on locally maximizing power performance within load constraints. For the experimental tests, the tip model is instrumented with spanwise bands of pressure sensors and is tested in the Poul la Cour wind tunnel at the Technical University of Denmark (DTU). The methods used for the numerical tests consisted of a blade element model, a near-wake model, lifting-line free-wake models, and a fully resolved Navier–Stokes solver. The comparison of the numerical and the experimental test results is performed for a given range of angles of attack and wind speeds, which is representative of the expected conditions in operation. Results show that the blade element model cannot predict the measured normal force coefficients, but the other methods are generally in good agreement with the measurements in attached flow. Flow visualization and pressure distribution compare well with computational fluid dynamics (CFD) simulations. The agreement in the clean case is better than in the tripped case at the inboard sections. Some uncertainties regarding the effect of the boundary layer at the inboard tunnel wall and the post-stall behavior remain.

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Section: Tip Model Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Wind tunnel testing of a swept tip shape and comparison with multi-fidelity aerodynamic simulations

et al. 2021

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“…Studies involving the application of the FSI framework, for both operational and standstill configurations, include Heinz et al (2016a, b) and Horcas et al (2019Horcas et al ( , 2020. The framework has been validated with experiments through simulations of a pull-release test of a wind turbine blade in the large-scale test facility of DTU; see Grinderslev et al (2020a).…”

Section: Fsi Frameworkmentioning

confidence: 99%

Wind turbines in atmospheric flow: fluid–structure interaction simulations with hybrid turbulence modeling

Grinderslev

Sørensen²,

Horcas

et al. 2021

Wind Energ. Sci.

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Abstract. In order to design future large wind turbines, knowledge is needed about the impact of aero-elasticity on the rotor loads and performance and about the physics of the atmospheric flow surrounding the turbines. The objective of the present work is to study both effects by means of high-fidelity rotor-resolved numerical simulations. In particular, unsteady computational fluid dynamics (CFD) simulations of a 2.3 MW wind turbine are conducted, this rotor being the largest design with relevant experimental data available to the authors. Turbulence is modeled with two different approaches. On one hand, a model using the well-established technique of improved delayed detached eddy simulation (IDDES) is employed. An additional set of simulations relies on a novel hybrid turbulence model, developed within the framework of the present work. It consists of a blend of a large-eddy simulation (LES) model by Deardorff for atmospheric flow and an IDDES model for the separated flow near the rotor geometry. In the same way, the assessment of the influence of the blade flexibility is performed by comparing two different sets of computations. The first group accounts for a structural multi-body dynamics (MBD) model of the blades. The MBD solver was coupled to the CFD solver during run time with a staggered fluid–structure interaction (FSI) scheme. The second set of simulations uses the original rotor geometry, without accounting for any structural deflection. The results of the present work show no significant difference between the IDDES and the hybrid turbulence model. In a similar manner, and due to the fact that the considered rotor was relatively stiff, the loading variation introduced by the blade flexibility was found to be negligible when compared to the influence of inflow turbulence. The simulation method validated here is considered highly relevant for future turbine designs, where the impact of blade elasticity will be significant and the detailed structure of the atmospheric inflow will be important.

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“…The tip shape presented in this work is the result of an aeroelastic optimization for maximizing power performance within load constraints for a tip mounted on DTU's rotating test rig (RTR) (Madsen et al, 2015;Ai et al, 2019). The optimization method used is the same as the one described in (Barlas et al, 2020), used for the tip design of a full scale wind turbine. The method of optimizing the tip for the RTR is essentially the same, while the baseline geometry and load envelope is defined by a reference straight tip, designed for an optimal BEM performance.…”

Section: Tip Model Designmentioning

confidence: 99%

Wind tunnel testing of a swept tip shape and comparison with multi-fidelity aerodynamic simulations

Barlas¹,

Pirrung²,

Ramos‐García³

et al. 2021

Preprint

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Abstract. One promising design solution for increasing the efficiency of modern horizontal axis wind turbines is the installation of curved tip extensions. However, introducing such complex geometries may move traditional aerodynamic models based on Blade Element Momentum (BEM) theory out of their range of applicability. This motivated the present work, where a swept tip shape is investigated by means of both experimental and numerical tests. The latter group accounted for a wide variety of aerodynamic models, allowing to highlight the capabilities and limitations of each of them in a relative manner. The considered swept tip shape is the result of a design optimization, focusing on locally maximizing power performance within load constraints. For the experimental tests, the tip model is instrumented with spanwise bands of pressure sensors and is tested in the Poul la Cour wind tunnel at the Technical University of Denmark (DTU). The methods used for the numerical tests consisted of a blade element model, a near-wake model, lifting-line free-wake models, and a fully resolved Navier- Stokes solver. The comparison of the numerical and the experimental tests results is performed for a given range of angles of attack and wind speeds, which is representative of the expected conditions in operation. Results show that the blade element model cannot predict the measured normal force coefficients, but the other methods are generally in good agreement with the measurements in attached flow. Flow visualization and pressure distribution compare well with Computational Fluid Dynamics (CFD) simulations. The agreement in the clean case is better than in the tripped case, indicating an aggressive tripping of the flow in the measurements. Some uncertainties regarding the effect of the boundary layer at the inboard tunnel wall and the post stall behavior remain.

show abstract

Vortex induced vibrations of wind turbine blades: Influence of the tip geometry

Cited by 45 publications

References 83 publications

Wind tunnel testing of a swept tip shape and comparison with multi-fidelity aerodynamic simulations

Wind tunnel testing of a swept tip shape and comparison with multi-fidelity aerodynamic simulations

Wind turbines in atmospheric flow: fluid–structure interaction simulations with hybrid turbulence modeling

Wind tunnel testing of a swept tip shape and comparison with multi-fidelity aerodynamic simulations

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