Dynamic inflow effects in measurements  and high-fidelity computations

Pirrung, Georg Raimund; Madsen, Helge Aagaard

doi:10.5194/wes-3-545-2018

Cited by 21 publications

(36 citation statements)

References 7 publications

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“…Note that the exponential approximation is using two exponential terms. It is shown to be better than using one or three, which is consistent with the recommendations from Pirrung and Madsen . The effect of using a different number of exponential terms to approximate the indicial functions is discussed further in Appendix B.…”

Section: Methodssupporting

confidence: 76%

“…This crucial discrepancy was not explored before because most of the previous research focused on the overall loads, eg, the moment at the blade root. The distribution of the dynamic‐inflow effect was investigated rarely in literature …”

Section: Resultsmentioning

confidence: 99%

“…The distribution of the dynamic-inflow effect was investigated rarely in literature. 10,20,21 The difference between all the engineering models and the CFD results in both the phase delay and the amplitude is larger near the tip. This shows that all the engineering models can be improved for dynamic induction at the tip.…”

Section: Radial Velocity Distributionmentioning

confidence: 97%

“…It is shown to be better than using one or three, which is consistent with the recommendations from Pirrung and Madsen. 10 The effect of using a different number of exponential terms to approximate the indicial functions is discussed further in Appendix B. In this paper, only the approximation of the induced velocity at the actuator disc is investigated, because the induction on the actuator disc is of most interest.…”

Section: Indicial Functionsmentioning

confidence: 99%

“…Pirrung and Madsen explained why it is better to use two time constants in Equation . The first time constant reflects the velocity delay induced by the (very) near wake (until 0.75D behind the rotor) where there is a strong dependency of distance to the tip vortex along the blade radial position.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

New dynamic‐inflow engineering models based on linear and nonlinear actuator disc vortex models

Tavernier

Ferreira

et al. 2019

Wind Energy

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Two new engineering models are presented for the aerodynamic induction of a wind turbine under dynamic thrust. The models are developed using the differential form of Duhamel integrals of indicial responses of actuator disc type vortex models. The time constants of the indicial functions are obtained by the indicial responses of a linear and a nonlinear actuator disc model. The new dynamic‐inflow engineering models are verified against the results of a Computational Fluid Dynamics (CFD) model and compared against the dynamic‐inflow engineering models of Pitt‐Peters, Øye, and Energy Research Center of the Netherlands (ECN), for several load cases. Comparisons of all models show that two time constants are necessary to predict the dynamic induction. The amplitude and phase delay of the velocity distribution shows a strong radial dependency. Verifying the models against results from the CFD model shows that the model based on the linear actuator disc vortex model predicts a similar performance as the Øye model. The model based on the nonlinear actuator disc vortex model predicts the dynamic induction better than the other models concerning both phase delay and amplitude, especially at high load.

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Section: Methodssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Section: Radial Velocity Distributionmentioning

confidence: 97%

Section: Indicial Functionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New dynamic‐inflow engineering models based on linear and nonlinear actuator disc vortex models

Tavernier

Ferreira

et al. 2019

Wind Energy

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A new dynamic inflow model for vertical‐axis wind turbines

Tavernier

Ferreira

2020

Wind Energy

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This paper presents a new dynamic inflow model for vertical-axis wind turbines (VAWTs). The model uses the principle of Duhamel's integral. The indicial function of the inflow-and crossflow-induction required to apply Duhamel's integral is represented by an exponential function depending on the thrust coefficient and the azimuthal position. The parameters of this approximation are calibrated using a free wake vortex model. The model is compared with the results of a vortex model and higher fidelity computational fluid dynamic (CFD) simulations for the response of an actuator cylinder to a step input of the thrust and to a cyclic thrust. It is found that the discrepancies of the dynamic inflow model increase with increasing reduced frequency and baseline thrust. However, the deviations remain small. Analysing the application of a finite-bladed floating VAWT with non-uniform loading and validating it against actuator line CFD results that intrinsically include dynamic inflow shows that the new dynamic inflow model significantly outperforms the Larsen and Madsen model (which is the current standard in fully coupled VAWT models) and enhances the modelling of VAWTs.

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The aerodynamics of a blade pitch, rotor speed, and surge step for a wind turbine regarding dynamic inflow

2022

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Floater motions introduce unsteadiness in the aerodynamics of floating offshore wind turbines. The aerodynamics of a wind turbine after three perturbations are studied: a blade pitch step, a rotor speed step for which dynamic inflow is expected, and a surge velocity step. The free vortex wake method and an analytical helical vortex model based on the Joukowsky rotor model are used to study the dynamic behavior of the induced velocity at the blades. As expected, the dynamic inflow effect is clear for the blade pitch and rotor speed changes, but for a surge velocity step, the models show that very little dynamic inflow effect takes place because the velocity induced by the vortex helix is not significantly modified: the tip vortex helix circulation change is partially compensated by the geometry change of the helix. For the rate of change, the velocities induced on the rotor by the vortex helix for the pitch and rotor speed changes show a rapid adjustment at the blade tip, with a slower change throughout the rest of the blade and at the center of the rotor.The convection velocity of the tip vortices is shown to be the main variable of the temporal evolution of the dynamic inflow effect.

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Dynamic inflow effects in measurements and high-fidelity computations

Cited by 21 publications

References 7 publications

New dynamic‐inflow engineering models based on linear and nonlinear actuator disc vortex models

New dynamic‐inflow engineering models based on linear and nonlinear actuator disc vortex models

A new dynamic inflow model for vertical‐axis wind turbines

The aerodynamics of a blade pitch, rotor speed, and surge step for a wind turbine regarding dynamic inflow

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