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

Barlas, Thanasis K.; Pirrung, Georg Raimund; Ramos‐García, Néstor; Horcas, Sergio González; Mikkelsen, Robert Flemming; Olsen, Anne-Marie Schjerning; Gaunaa, Mac

doi:10.5194/wes-6-1311-2021

Cited by 9 publications

(14 citation statements)

References 20 publications

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“…Finally, it would be very relevant to validate the numerical results against experimental data in future studies (see, e.g., Barlas et al, 2021a).…”

Section: Future Workmentioning

confidence: 96%

CFD-based curved tip shape design for wind turbine blades

Madsen¹,

Zahle²,

Horcas³

et al. 2022

Wind Energ. Sci.

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Abstract. This work presents a high-fidelity shape optimization framework based on computational fluid dynamics (CFD). The presented work is the first comprehensive curved tip shape study of a wind turbine rotor to date using a direct CFD-based approach. Preceding the study is a thorough literature survey particularly focused on wind turbine blade tips in order to place the present work in its context. Then follows a comprehensive analysis to quantify mesh dependency and to present needed mesh modifications ensuring a deep convergence of the flow field at each design iteration. The presented modifications allow the framework to produce up to six-digit-accurate finite difference gradients which are verified using the machine-accurate Complex-Step method. The accurate gradients result in a tightly converged design optimization problem in which the studied problem is to maximize power using 12 design variables while satisfying constraints on geometry, as well as on the bending moment at 90 % blade length. The optimized shape has about 1 % r/R blade extension, 2 % r/R flapwise displacement, and slightly below 2 % r/R edgewise displacement resulting in a 1.12 % increase in power. Importantly, the inboard part of the tip is de-loaded using twist and chord design variables as the blade is extended, ensuring that the baseline steady-state loads are not exceeded. For both analysis and optimization an industrial-scale mesh resolution of above 14×106 cells is used, which underlines the maturity of the framework.

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“…Finally, it would be very relevant to validate the numerical results against experimental data in future studies (see, e.g., Barlas et al, 2021a).…”

Section: Future Workmentioning

confidence: 96%

CFD-based curved tip shape design for wind turbine blades

Madsen¹,

Zahle²,

Horcas³

et al. 2022

Wind Energ. Sci.

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“…Four tip extensions with different geometric properties are simulated in this work. A more detailed description of the SmartTip project is provided in [11,12,13,14]. All tip extensions simulated within the present work are shown in figure 1.…”

Section: Smarttip Geometriesmentioning

confidence: 99%

Comparison of different fidelity aerodynamic solvers on the IEA 10 MW turbine including novel tip extension geometries

Luna

Marten

Barlas

et al. 2022

J. Phys.: Conf. Ser.

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Lifting-line based solvers could supersede the blade element momentum (BEM) method as the industry standard in the near future as rotor sizes of modern wind turbines and computational resources continue to increase. A comparison study between both methods is presented where the IEA 10 MW wind turbine is evaluated in the aero-servo-elastic simulation tool QBlade, comparing the lifting-line free vortex wake method to an unsteady blade element momentum solver. Besides the baseline rotor of the IEA 10 MW turbine, the comparison includes several blade tip extensions, including a swept and a dihedral geometry, to further differentiate capabilities between both methods in aerodynamically complex flow fields. As a reference serve results from equivalent simulations performed with multiple fidelity solvers of the simulation tool HAWC2. Results of a rigid load case demonstrate considerable improvement regarding the aerodynamic accuracy of lifting-line based methods in below rated conditions over BEM codes. The aerodynamic loads on geometrically complex tip extensions in steady conditions prove good capabilities of lower fidelity codes to predict out-of-plane bend shapes but also clear limitations regarding loads on swept geometries. A quasi-steady aeroelastic load case further demonstrates the capability of both QBlade codes to produce comparable results to similar fidelity solvers of the HAWC2 tool on an integral level. A detailed comparison in the time domain shows a larger dependency of the results on the type of structural solver that is used in contrast to the fidelity level of the aerodynamic method.

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“…This factor is based on the grid line normal distance to the surface and ensures that mesh cells close to the surface are moved as rigid cells, while further from the surface the cells are deformed based on the distance. The solver has been extensively used and validated through multiple studies of wind turbines; see for instance the Mexico project (Bechmann et al, 2011;Sørensen et al, 2016), the Phase VI NREL rotor simulations (Sørensen and Schreck, 2014;Sørensen et al, 2002), and recent comparisons with wind tunnel tests of a curved blade tip (Barlas et al, 2021) and with the full scale DanAero measurements (Madsen et al, 2018;Grinderslev et al, 2020b;Schepers et al, 2021).…”

Section: Flow Solvermentioning

confidence: 99%

Multiple limit cycle amplitudes in high fidelity predictions of standstill wind turbine blade vibrations

Grinderslev

Sørensen

Pirrung

et al. 2022

Preprint

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Abstract. In this study, vortex induced vibrations (VIVs) on the IEA10MW blade are investigated using two methodologies in order to assess strengths and weaknesses of the two simulation types. Both fully coupled fluid-structure interaction (FSI) simulations and computational fluid dynamics (CFD) with forced motion of the blade are used and compared. It is found that for the studied cases with high inclination angles, the forced motion simulations succeed in capturing the power injection by the aerodynamics, despite the motion being simplified. From the fully coupled simulations, a dependency of initial conditions of the vibrations was found, showing that cases which are stable if unperturbed, might go into large VIVs if provoked initially by for instance inflow turbulence or turbine operations. Depending on the initial vibration amplitudes, multiple limit cycle levels can be triggered, for the same flow case, due to the non-linearity of the aerodynamics. By fitting a simple damping model for the specific blade and mode shape from FSI simulations, it is also demonstrated that the equilibrium limit cycle amplitudes between power injection and dissipation can be estimated using forced motion simulations, even for the multiple stable vibration cases, with good agreement to fully coupled simulations. Finally, a time series generation from forced motion simulations and the simple damping model is presented, concluding that CFD amplitude sweeps can estimate not only the final limit cycle oscillation amplitude, but also the vibration build-up time series.

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

Cited by 9 publications

References 20 publications

CFD-based curved tip shape design for wind turbine blades

CFD-based curved tip shape design for wind turbine blades

Comparison of different fidelity aerodynamic solvers on the IEA 10 MW turbine including novel tip extension geometries

Multiple limit cycle amplitudes in high fidelity predictions of standstill wind turbine blade vibrations

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