A simple improvement of a tip loss model for actuator disc simulations

Pirrung, Georg Raimund; Laan, P. van der; Ramos‐García, Néstor; Forsting, Alexander Meyer

doi:10.1002/we.2481

Cited by 6 publications

(7 citation statements)

References 32 publications

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“…Of the LES and RANS models, again only LES DTU predicts a decay of F t . The other models show a typical bump that originates from the spurious induction of the trailing tip vortex [77] (or the vortex sheet for the ADM in RANS UU , respectively [91]). When compared to Case A, DWM DTU is in closer agreement with most of the LES models.…”

Section: Power and Loads Of The Downstream Turbinementioning

confidence: 99%

Wind Turbine Response in Waked Inflow: A Modelling Benchmark Against Full-Scale Measurements

et al. 2021

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Section: Power and Loads Of The Downstream Turbinementioning

confidence: 99%

Wind Turbine Response in Waked Inflow: A Modelling Benchmark Against Full-Scale Measurements

et al. 2021

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“…The factor multiplying p in Equation ( 18) is identical to i w,b for a vortex of constant radius, t = 1, at the "equivalent pitch" of p * = p 2 + k 2 * . This changes the equation for F w from Equation (6) to…”

Section: Resultsmentioning

confidence: 99%

“…Modifications to Prandtl's formulation have been developed by a number of authors, including Shen et al [5]. A more recent example of this type of analysis is by [6]. None of these modificatons address the effects of wake expansion.…”

Section: Introductionmentioning

confidence: 99%

Wake Expansion and the Finite Blade Functions for Horizontal-Axis Wind Turbines

Wood

2021

Energies

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This paper considers the effect of wake expansion on the finite blade functions in blade element/momentum theory for horizontal-axis wind turbines. For any velocity component, the function is the ratio of the streamtube average to that at the blade elements. In most cases, the functions are set by the trailing vorticity only and Prandtl’s tip loss factor can be a reasonable approximation to the axial and circumferential functions at sufficiently high tip speed ratio. Nevertheless, important cases like coned or swept rotors or shrouded turbines involve more complex blade functions than provided by the tip loss factor or its recent modifications. Even in the presence of significant wake expansion, the functions derived from the exact solution for the flow due to constant pitch and radius helical vortices provide accurate estimates for the axial and circumferential blade functions. Modifying the vortex pitch in response to the expansion improves the accuracy of the latter. The modified functions are more accurate than the tip loss factor for the test cases at high tip speed ratio that are studied here. The radial velocity is important for expanding flow as it has the magnitude of the induced axial velocity near the edge of the rotor. It is shown that the resulting angle of the flow to the axial direction is small even with significant expansion, as long is the tip speed ratio is high. This means that blade element theory does not have account for the effective blade sweep due to the radial velocity. Further, the circumferential variation of the radial velocity is lower than of the other components.

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“…In fact, provided that the profile drag remains essentially constant in the considered region of the wing, and that the lift coefficient is corrected to match the reference results, then the error on the drag distribution necessarily originates from a misprediction of the downwash. As also shown by Pirrung et al (2020), it is therefore preferable to correct the effective angle of attack to obtain the correct drag, while also maintaining a correct value for the lift. This is possible due to the small value of the downwash angle.…”

Section: Correction Function For the Angle Of Attackmentioning

confidence: 99%

“…This correction was then extended by Wimshurst & Willden (2017) by comparing ALM to blade-resolved simulations and deriving separate correction functions for the normal and tangential loads. Pirrung et al (2020) then showed that applying the Shen correction to the angle of attack led to an improved accuracy of the normal and tangential loads. Sørensen et al (2016) also developed a decambering correction to take into account the variation of the induced velocity on the blade surface when using a lifting line approach.…”

Section: Introductionmentioning

confidence: 99%

Near-tip correction functions for the actuator line method to improve the predicted lift and drag distributions

Trigaux,

Villeneuve,

Dumas

et al. 2024

J. Fluid Mech.

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The actuator line method (ALM) is a commonly used technique to simulate slender lifting and dragging bodies such as wings or blades. However, the accuracy of the method is significantly reduced near the tip. To quantify the loss of accuracy, translating wings with various aspect and taper ratios are simulated using several methods: wall-resolved Reynolds-averaged Navier–Stokes (RANS) simulations, an advanced ALM with two-dimensional (2-D) mollification of the force, a lifting line method, a mollified lifting line method and a vortex lattice method. Significant differences in the lift and drag distributions are found on the part of the wing where the distance to the tip is smaller than approximately 3 chords and are identified to arise from both the forces mollification and the uneven induced velocity along the chord. Correction functions acting on the lift coefficient and effective angle of attack near the wing tip are then derived for rectangular wings of various aspect ratios. They are then also applied to wings of various taper ratios using the ‘effective dimensionless distance to the tip’ as the main parameter. The application of the correction not only leads to a much improved lift distribution, but also to a more consistent drag distribution. The correction functions are also obtained for various mollification sizes, as well as for ALM with three-dimensional (3-D) mollification. These changes mostly impact the correction for the effective angle of attack. Finally, the correction is applied to simulations of the NREL Phase VI wind turbine, leading to an enhanced agreement with the experimental data.

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A simple improvement of a tip loss model for actuator disc simulations

Cited by 6 publications

References 32 publications

Wind Turbine Response in Waked Inflow: A Modelling Benchmark Against Full-Scale Measurements

Wind Turbine Response in Waked Inflow: A Modelling Benchmark Against Full-Scale Measurements

Wake Expansion and the Finite Blade Functions for Horizontal-Axis Wind Turbines

Near-tip correction functions for the actuator line method to improve the predicted lift and drag distributions

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