A computationally efficient engineering aerodynamic model for non-planar wind turbine rotors

Li, Ang; Gaunaa, Mac; Pirrung, Georg Raimund; Horcas, Sergio González

doi:10.5194/wes-2021-100

Cited by 5 publications

(27 citation statements)

References 22 publications

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“…The blade element vortex cylinder (BEVC) method is the combination of the blade element theory and the vortex cylinder model. It has been shown in a previous work (Li et al, 2021) that the distributed loads of dihedral blades predicted by the BEVC model agree significantly better with higher-fidelity LL and fully-resolved CFD, than BEM results. In that previous work, it was described that the unsteady airfoil aerodynamic effects are included in the numerical tests, which is actually done work, the results with and without the correction will be compared to show the importance of the effect.…”

Section: Bevc Methodsmentioning

confidence: 79%

“…This is because the influence of the dihedral on the distributed loads is partially canceled out when calculating the power and thrust of the whole rotor. In contrast, the improvement of BEVC over BEM when predicting thrust and power is significant when computing the rotors with curved dihedral blades as shown in the previous work (Li et al, 2021).…”

Section: Integrated Aerodynamic Loadsmentioning

confidence: 82%

“…In order to ensure the quality of the comparison among different blade geometries involved in the present study, it is important to define the loads in a consistent manner. The loads are defined as force per unit radius, which is the same definition used in the previous work (Li et al, 2021). The sectional aerodynamic loads that are calculated from the 2-D airfoil data and projected into the rotor coordinate system should correspond to force per unit curved blade length.…”

Section: Resultsmentioning

confidence: 99%

“…For the coned straight blade case, the correction factor is equal to the secant of the cone angle. For the dihedral blade with added coning, the correction factor is equal to the secant of the sum of the cone angle and the local dihedral angle (Li et al, 2021). conditions under uniform inflow perpendicular to the rotor plane is approximately zero.…”

Section: Resultsmentioning

confidence: 99%

“…The upwind dihedral blade is modified from the baseline straight blade so that the half-chord line has out-of-plane shapes. The geometry of the upwind dihedral blade is identical to the W-1 blade in a previous study (Li et al, 2021). The blade has the same radius as the straight blade but is bending upwind from 50% of radius until the blade tip.…”

Section: Blade Geometries For Comparisonmentioning

confidence: 99%

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How should the lift and drag forces be calculated from 2-D airfoil data for dihedral or coned wind turbine blades?

Gaunaa

Pirrung

et al. 2022

Preprint

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Abstract. In the present work, a consistent method for calculating the lift and drag forces from the 2-D airfoil data for the dihedral or coned horizontal-axis wind turbines when using generalized lifting-line methods is described. The generalized lifting-line methods include, for example, lifting-line (LL), actuator line (AL), blade element momentum (BEM) and blade element vortex cylinder (BEVC) methods. A consistent interpretation of classic unsteady 2-D thin airfoil theory results for use in a generally moving frame of reference within a linearly varying onset velocity field reveals that it is necessary to use not only the relative flow magnitude and direction at one point along the chord line (for instance three-quarter-chord), but also the gradient of the flow direction in the chordwise direction (or, equivalently, the flow direction at the quarter-chord) to correctly determine the magnitude and direction of the resulting 2-D aerodynamic forces and moment. However, this aspect is generally overlooked and most implementations in generalized lifting-line methods use only the flow information at one calculation point per section for simplicity. This simplification will not change the performance prediction of planar rotors, but will cause an error when applied to non-planar rotors. The present work proposes a generalized method to correct the error introduced by this simplified single-point calculation method. In this work this effect is investigated using the special case, where the wind turbine blade has only dihedral and no sweep, operating at steady-state conditions with uniform inflow applied perpendicular to the rotor plane. We investigate the impact of the effect by comparing the predictions of the steady-state performance of non-planar rotors from the consistent approach with the simplified one-point approach of the LL method. The results are verified using blade geometry resolving Reynolds-averaged Navier-Stokes (RANS) simulations. The numerical investigations confirmed that the correction derived from thin airfoil theory is needed for the calculations to correctly determine the magnitude and direction of the sectional aerodynamic forces for non-planar rotors. The aerodynamic loads of upwind and downwind coned blades that are calculated using the LL method, the BEM method, the BEVC method and the AL method are compared for the simplified and the full method. Results using the full method, including different specific implementation schemes, are shown to agree significantly better with fully-resolved RANS than the often used simplified one-point approaches.

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Section: Bevc Methodsmentioning

confidence: 79%

Section: Integrated Aerodynamic Loadsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Blade Geometries For Comparisonmentioning

confidence: 99%

See 3 more Smart Citations

How should the lift and drag forces be calculated from 2-D airfoil data for dihedral or coned wind turbine blades?

Gaunaa

Pirrung

et al. 2022

Preprint

Self Cite

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Comparison of aerodynamic models for horizontal axis wind turbine blades accounting for curved tip shapes

Horcas

Ramos‐García

et al. 2022

Wind Energy

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Curved tip extensions are among the rotor innovation concepts that can contribute to the higher performance and lower cost of horizontal axis wind turbines. One of the key drivers to exploit their advantages is the use of accurate and efficient computational aerodynamic models during the design stage. The present work gives an overview of the performance of different state-of-the-art models. The following tools were employed, in descending order of complexity: (i) a blade-resolved Navier Stokes solver, (ii) a lifting line model, (iii) a vortex-based method coupling a near-wake model with a far-wake model, and (iv) two implementations of the widely used blade element momentum method (BEM), with and without radial induction. The predictions of the codes were compared when simulating the baseline geometry of a reference wind turbine and different tip extension designs with relatively large sweep angle and/or dihedral angle. Four load cases were selected for this comparison, to cover several aspects of the aerodynamic modeling: steady power curve, pitch step, extreme operating gust impact, and standstill in deep stall. The present study highlighted the limitations of the BEM-based formulations to capture the trends attributed to the introduction of curvature at the tip. This was true even when using the radial induction submodel. The rest of the computational methods showed relatively good agreement in most of the studied load cases. An exception to this was the standstill configuration, as the blade-resolved Navier-Stokes solver was the only code able to capture the highly unsteady effects of deep stall.

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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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A computationally efficient engineering aerodynamic model for non-planar wind turbine rotors

Cited by 5 publications

References 22 publications

How should the lift and drag forces be calculated from 2-D airfoil data for dihedral or coned wind turbine blades?

How should the lift and drag forces be calculated from 2-D airfoil data for dihedral or coned wind turbine blades?

Comparison of aerodynamic models for horizontal axis wind turbine blades accounting for curved tip shapes

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

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