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Wind Energy Science
The interactive open-access journal of the European Academy of Wind Energy
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WES | Articles | Volume 4, issue 1
Wind Energ. Sci., 4, 1–21, 2019
https://doi.org/10.5194/wes-4-1-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wes-4-1-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
Wind Energ. Sci., 4, 1–21, 2019
https://doi.org/10.5194/wes-4-1-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wes-4-1-2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article 08 Jan 2019
Research article | 08 Jan 2019
Aerodynamic characterization of a soft kite by in situ flow measurement
Johannes Oehler and Roland Schmehl
Related authors
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Mark Schelbergen, Peter C. Kalverla, Roland Schmehl, and Simon J. Watson
Wind Energ. Sci., 5, 1097–1120, https://doi.org/10.5194/wes-5-1097-2020, https://doi.org/10.5194/wes-5-1097-2020, 2020
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We have presented a methodology for including multiple wind profile shapes in a wind resource description that are identified using a data-driven approach. These shapes go beyond the height range for which conventional wind profile relationships are developed. Moreover, they include non-monotonic shapes such as low-level jets. We demonstrated this methodology for an on- and offshore reference location using DOWA data and efficiently estimated the annual energy production of a pumping AWE system.
Jan Hummel, Dietmar Göhlich, and Roland Schmehl
Wind Energ. Sci., 4, 41–55, https://doi.org/10.5194/wes-4-41-2019, https://doi.org/10.5194/wes-4-41-2019, 2019
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We describe a tow test setup for the reproducible measurement of aerodynamic, structural dynamic and flight dynamic properties of tethered membrane wings. The test procedure is based on repeatable automated maneuvers with the entire kite system under realistic conditions. The developed measurement method can be used to quantitatively compare different wing designs, to validate and improve simulation models, and to systematically improve kite designs.
Tarek N. Dief, Uwe Fechner, Roland Schmehl, Shigeo Yoshida, Amr M. M. Ismaiel, and Amr M. Halawa
Wind Energ. Sci., 3, 275–291, https://doi.org/10.5194/wes-3-275-2018, https://doi.org/10.5194/wes-3-275-2018, 2018
Related subject area
Aerodynamics and hydrodynamics
Aerodynamic effects of Gurney flaps on the rotor blades of a research wind turbine
Identification of airfoil polars from uncertain experimental measurements
Laminar-turbulent transition characteristics of a 3-D wind turbine rotor blade based on experiments and computations
Parametric slat design study for thick-base airfoils at high Reynolds numbers
An improved second-order dynamic stall model for wind turbine airfoils
The flow past a flatback airfoil with flow control devices: benchmarking numerical simulations against wind tunnel data
On the velocity at wind turbine and propeller actuator discs
Cartographing dynamic stall with machine learning
Pressure Based Lift Estimation and its Application to Feedforward Load Control employing Trailing Edge Flaps
Top-level rotor optimisations based on actuator disc theory
Two-dimensional numerical simulations of vortex-induced vibrations for a cylinder in conditions representative of wind turbine towers
Validation and accommodation of vortex wake codes for wind turbine design load calculations
Improving wind farm flow models by learning from operational data
Actuator line simulations of wind turbine wakes using the lattice Boltzmann method
Development of a second-order dynamic stall model
Investigations of aerodynamic drag forces during structural blade testing using high-fidelity fluid–structure interaction
Ability of the e-TellTale sensor to detect flow features over wind turbine blades: flow stall/reattachment dynamics
Brief communication: A fast vortex-based smearing correction for the actuator line
Field test of an active flap system on a full scale wind turbine
Brief communication: A double-Gaussian wake model
Determination of the Angle of Attack on a Research Wind Turbine Rotor Blade Using Surface Pressure Measurements
The effect of wind direction shear on turbine performance in a wind farm in central Iowa
Implementation of the blade element momentum model on a polar grid and its aeroelastic load impact
Derivation of an Impulse Equation for Wind Turbine Thrust
Brief communication: Wind-speed-independent actuator disk control for faster annual energy production calculations of wind farms using computational fluid dynamics
Performance study of the QuLAF pre-design model for a 10 MW floating wind turbine
Multi-element ducts for ducted wind turbines: a numerical study
A vortex-based tip/smearing correction for the actuator line
Power curve and wake analyses of the Vestas multi-rotor demonstrator
Qualitative yaw stability analysis of free-yawing downwind turbines
The aerodynamics of the curled wake: a simplified model in view of flow control
Wake behavior and control: comparison of LES simulations and wind tunnel measurements
Blind test comparison on the wake behind a yawed wind turbine
Advanced computational fluid dynamics (CFD)–multi-body simulation (MBS) coupling to assess low-frequency emissions from wind turbines
An efficient frequency-domain model for quick load analysis of floating offshore wind turbines
Probabilistic forecasting of wind power production losses in cold climates: a case study
Dynamic inflow effects in measurements and high-fidelity computations
Numerical analyses and optimizations on the flow in the nacelle region of a wind turbine
Simulation of transient gusts on the NREL 5 MW wind turbine using the URANS solver THETA
About the suitability of different numerical methods to reproduce model wind turbine measurements in a wind tunnel with a high blockage ratio
The second curvature correction for the straight segment approximation of periodic vortex wakes
Wind tunnel experiments on wind turbine wakes in yaw: effects of inflow turbulence and shear
How does turbulence change approaching a rotor?
Wind tunnel experiments on wind turbine wakes in yaw: redefining the wake width
Ducted wind turbine optimization and sensitivity to rotor position
Assessment of wind turbine component loads under yaw-offset conditions
Modeling of quasi-static thrust load of wind turbines based on 1 s SCADA data
Free-flow wind speed from a blade-mounted flow sensor
A model for quick load analysis for monopile-type offshore wind turbine substructures
Extraction of the wake induction and angle of attack on rotating wind turbine blades from PIV and CFD results
Jörg Alber, Rodrigo Soto-Valle, Marinos Manolesos, Sirko Bartholomay, Christian Navid Nayeri, Marvin Schönlau, Christian Menzel, Christian Oliver Paschereit, Joachim Twele, and Jens Fortmann
Wind Energ. Sci., 5, 1645–1662, https://doi.org/10.5194/wes-5-1645-2020, https://doi.org/10.5194/wes-5-1645-2020, 2020
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The aerodynamic impact of Gurney flaps is investigated on the rotor blades of the Berlin Research Turbine. The findings of this research project contribute to performance improvements of different-size rotor blades. Gurney flaps are considered a worthwhile passive flow-control device in order to alleviate the adverse effects of both early separation in the inner blade region and leading-edge erosion throughout large parts of the blade span.
Chengyu Wang, Filippo Campagnolo, and Carlo L. Bottasso
Wind Energ. Sci., 5, 1537–1550, https://doi.org/10.5194/wes-5-1537-2020, https://doi.org/10.5194/wes-5-1537-2020, 2020
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A new method is described to identify the aerodynamic characteristics of blade airfoils directly from operational data of the turbine. Improving on a previously published approach, the present method is based on a new maximum likelihood formulation that includes errors both in the outputs and the inputs. The method is demonstrated on the identification of the polars of small-scale turbines for wind tunnel testing.
Özge Sinem Özçakmak, Helge Aagaard Madsen, Niels Nørmark Sørensen, and Jens Nørkær Sørensen
Wind Energ. Sci., 5, 1487–1505, https://doi.org/10.5194/wes-5-1487-2020, https://doi.org/10.5194/wes-5-1487-2020, 2020
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Accurate prediction of the laminar-turbulent transition process is critical for design and prediction tools to be used in the industrial design process, particularly for the high Reynolds numbers experienced by modern wind turbines. Laminar-turbulent transition behavior of a wind turbine blade section is investigated in this study by means of field experiments and 3-D computational fluid dynamics (CFD) rotor simulations.
Julia Steiner, Axelle Viré, Francesco Benetti, Nando Timmer, and Richard Dwight
Wind Energ. Sci., 5, 1075–1095, https://doi.org/10.5194/wes-5-1075-2020, https://doi.org/10.5194/wes-5-1075-2020, 2020
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The manuscript deals with the aerodynamic design of slat elements for thick-base airfoils at high Reynolds numbers using integral boundary layer and computational fluid dynamics models. The results highlight aerodynamic benefits such as high stall angle, low roughness sensitivity, and higher aerodynamic efficiency than standard single-element configurations. However, this is accompanied by a steep drop in lift post-stall and potentially issues related to the structural design of the blade.
Galih Bangga, Thorsten Lutz, and Matthias Arnold
Wind Energ. Sci., 5, 1037–1058, https://doi.org/10.5194/wes-5-1037-2020, https://doi.org/10.5194/wes-5-1037-2020, 2020
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Robust and accurate dynamic stall modeling remains one of the most difficult tasks in wind turbine load calculations despite its long research effort in the past. The present paper describes a new
second-order dynamic stall model for wind turbine airfoils. The new model is robust and improves the prediction for the aerodynamic forces and their higher-harmonic effects due to vortex shedding but also provides improved predictions for pitching moment and drag.
George Papadakis and Marinos Manolesos
Wind Energ. Sci., 5, 911–927, https://doi.org/10.5194/wes-5-911-2020, https://doi.org/10.5194/wes-5-911-2020, 2020
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Flatback airfoils are used in the root region of wind turbine blades since they have several structural and aerodynamic benefits. Several flow control devices are incorporated to mitigate the effects of vortex shedding in the wake of such airfoils. In this work, two different numerical approaches are compared to wind tunnel measurements to assess the suitability of each method for predicting the performance of the flow control devices in terms of loads and unsteady characteristics.
Gijs A. M. van Kuik
Wind Energ. Sci., 5, 855–865, https://doi.org/10.5194/wes-5-855-2020, https://doi.org/10.5194/wes-5-855-2020, 2020
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The paper compares actuator discs in propeller and wind turbine mode. At very low rotational speed, propeller discs have an expanding wake while still energy is put into the wake. The velocity at the disc in the plane containing the axis is practically uniform: a few per mille deviation for wind turbine discs and a few per cent for propeller discs. The deviations are caused by the different strengths of the singularity in the wake boundary vorticity strength at its leading edge.
Matthew Lennie, Johannes Steenbuck, Bernd R. Noack, and Christian Oliver Paschereit
Wind Energ. Sci., 5, 819–838, https://doi.org/10.5194/wes-5-819-2020, https://doi.org/10.5194/wes-5-819-2020, 2020
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This study presents a marriage of unsteady aerodynamics and machine learning. When airfoils are subjected to high inflow angles, the flow no longer follows the surface and the flow is said to be separated. In this flow regime, the forces experienced by the airfoil are highly unsteady. This study uses a range of machine learning techniques to extract infomation from test data to help us understand the flow regime and makes recomendations on how to model it.
Sirko Bartholomay, Tom T. B. Wester, Sebastian Perez-Becker, Simon Konze, Christian Menzel, Michael Hölling, Axel Spickenheuer, Joachim Peinke, Christian N. Nayeri, Oliver P. Paschereit, and Kilian Oberleithner
Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2020-91, https://doi.org/10.5194/wes-2020-91, 2020
Preprint under review for WES
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This paper presents two methods on how to estimate the lift force that is created by a wing. These methods were experimentally assessed in a wind tunnel. Furthermore, an active trailing edge flap, as seen on airplanes for example, is used to alleviate fluctuating loads that are created within the employed wind tunnel. Thereby, an active flow control device is examined that can be potentially serve on wind turbines to lower fatigue or lower the material used for the blades.
Peter Jamieson
Wind Energ. Sci., 5, 807–818, https://doi.org/10.5194/wes-5-807-2020, https://doi.org/10.5194/wes-5-807-2020, 2020
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Wind turbine rotors are usually designed to maximize power performance, accepting any loading results. However, from the most basic wind turbine theory, actuator disc theory, two other optimization paths are demonstrated, which may lead to more cost-effective technology – the low-induction rotor where an expanded rotor diameter and some extra power is achieved without increasing the blade root bending moment and the secondary rotor which can provide a very low torque and low-cost drivetrain.
Axelle Viré, Adriaan Derksen, Mikko Folkersma, and Kumayl Sarwar
Wind Energ. Sci., 5, 793–806, https://doi.org/10.5194/wes-5-793-2020, https://doi.org/10.5194/wes-5-793-2020, 2020
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Vortex-induced vibrations are structural vibrations that can occur due to the shedding of flow vortices when a fluid flow passes around a structure. Here, conditions specific to wind turbine towers are investigated numerically. The work highlights a complex interplay between structural and fluid dynamics. In particular, certain conditions lead to a continuous alternation between self-exciting and self-limiting vortex-induced vibrations, linked to a change in the sign of the aerodynamic damping.
Koen Boorsma, Florian Wenz, Koert Lindenburg, Mansoor Aman, and Menno Kloosterman
Wind Energ. Sci., 5, 699–719, https://doi.org/10.5194/wes-5-699-2020, https://doi.org/10.5194/wes-5-699-2020, 2020
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The present publication has contributed towards making vortex wake models ready for application to certification load calculations. The reduction in flapwise blade root moment fatigue loading using vortex wake models instead of the blade element momentum method has been verified using dedicated CFD simulations. A validation effort against a long-term field measurement campaign featuring 2.5 MW turbines has confirmed the improved prediction of unsteady load characteristics by vortex wake models.
Johannes Schreiber, Carlo L. Bottasso, Bastian Salbert, and Filippo Campagnolo
Wind Energ. Sci., 5, 647–673, https://doi.org/10.5194/wes-5-647-2020, https://doi.org/10.5194/wes-5-647-2020, 2020
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The paper describes a new method that uses standard historical operational data and reconstructs the flow at the rotor disk of each turbine in a wind farm. The method is based on a baseline wind farm flow and wake model, augmented with error terms that are
learnedfrom operational data using an ad hoc system identification approach. Both wind tunnel experiments and real data from a wind farm at a complex terrain site are used to show the capabilities of the new method.
Henrik Asmuth, Hugo Olivares-Espinosa, and Stefan Ivanell
Wind Energ. Sci., 5, 623–645, https://doi.org/10.5194/wes-5-623-2020, https://doi.org/10.5194/wes-5-623-2020, 2020
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The presented work investigates the potential of the lattice Boltzmann method (LBM) for numerical simulations of wind turbine wakes. The LBM is a rather novel, alternative approach for computational fluid dynamics (CFD) that allows for significantly faster simulations. The study shows that the method provides similar results when compared to classical CFD approaches while only requiring a fraction of the computational demand.
Niels Adema, Menno Kloosterman, and Gerard Schepers
Wind Energ. Sci., 5, 577–590, https://doi.org/10.5194/wes-5-577-2020, https://doi.org/10.5194/wes-5-577-2020, 2020
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It is crucial to model dynamic stall accurately to reduce inaccuracies in predicting fatigue and extreme loads. This paper investigates a new dynamic stall model. Improvements are proposed based on experiments. The updated model shows significant improvements over the initial model; however, further validation and research are still required. This updated model might be incorporated into future wind turbine design codes and will hopefully reduce inaccuracies in predicted wind turbine loads.
Christian Grinderslev, Federico Belloni, Sergio González Horcas, and Niels Nørmark Sørensen
Wind Energ. Sci., 5, 543–560, https://doi.org/10.5194/wes-5-543-2020, https://doi.org/10.5194/wes-5-543-2020, 2020
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This study focuses on coupled computational fluid and structural dynamics simulations of a dynamic structural test of a wind turbine blade, as performed in laboratories. It is found that drag coefficients used for simulations, when planning fatigue tests, underestimate air resistance to the dynamic motion that the blade undergoes during tests. If this is not corrected for, this can result in the forces applied to the blade actually being lower in reality during tests than what was planned.
Antoine Soulier, Caroline Braud, Dimitri Voisin, and Bérengère Podvin
Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2020-13, https://doi.org/10.5194/wes-2020-13, 2020
Revised manuscript under review for WES
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Paper about validation of Electronic TellTale sensors to support their use for wind turbine blade monitoring.
Alexander R. Meyer Forsting, Georg R. Pirrung, and Néstor Ramos-García
Wind Energ. Sci., 5, 349–353, https://doi.org/10.5194/wes-5-349-2020, https://doi.org/10.5194/wes-5-349-2020, 2020
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Simulations of wind farms allow the estimation of the forces acting on the turbines and thus their lifetime and power production. Representing the actual geometric shape of turbines in a realistic atmospheric flow is computationally expensive; therefore they are modelled in a simplified manner. Unfortunately, these simplifications negatively impact the estimated forces. We developed an open-source aerodynamic model that corrects the forces, giving more accurate estimates of lifetime and power.
Alejandro Gomez Gonzalez, Peder B. Enevoldsen, Athanasios Barlas, and Helge A. Madsen
Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2020-21, https://doi.org/10.5194/wes-2020-21, 2020
Revised manuscript accepted for WES
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This work describes a series of tests of active flaps on a large wind turbine. The measurements are performed between October 2017 and June 2019 using two different flap configurations on the blade of the turbine showing a potential to manipulate the loading of the turbine between 5% and 10 %. This project is performed with the aim of demonstrating a technology with the potential of reducing the levelized cost of energy for wind power.
Johannes Schreiber, Amr Balbaa, and Carlo L. Bottasso
Wind Energ. Sci., 5, 237–244, https://doi.org/10.5194/wes-5-237-2020, https://doi.org/10.5194/wes-5-237-2020, 2020
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An analytical wake model with a double-Gaussian velocity distribution is used to improve on a similar formulation by Keane et al (2016). The choice of a double-Gaussian shape function is motivated by the behavior of the near-wake region that is observed in numerical simulations and experimental measurements. The model is calibrated and validated using large eddy simulations replicating scaled wind turbine experiments, yielding improved results with respect to a classical single-Gaussian profile.
Rodrigo Soto-Valle, Sirko Bartholomay, Joerg Alber, Marinos Manolesos, Christian Navid Nayeri, and Christian Oliver Paschereit
Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2020-35, https://doi.org/10.5194/wes-2020-35, 2020
Revised manuscript accepted for WES
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In this paper, a method to determine the angle of attack on a wind turbine rotor blade using a pressure distribution measurement was applied. The tested method uses the information of a reduced number of pressure taps and is a significant step that eliminates the need for external probes, which affect the flow over the blade and require additional calibration.
Miguel Sanchez Gomez and Julie K. Lundquist
Wind Energ. Sci., 5, 125–139, https://doi.org/10.5194/wes-5-125-2020, https://doi.org/10.5194/wes-5-125-2020, 2020
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Wind turbine performance depends on various atmospheric conditions. We quantified the effect of the change in wind direction and speed with height (direction and speed wind shear) on turbine power at a wind farm in Iowa. Turbine performance was affected during large direction shear and small speed shear conditions and favored for the opposite scenarios. These effects make direction shear significant when analyzing the influence of different atmospheric variables on turbine operation.
Helge Aagaard Madsen, Torben Juul Larsen, Georg Raimund Pirrung, Ang Li, and Frederik Zahle
Wind Energ. Sci., 5, 1–27, https://doi.org/10.5194/wes-5-1-2020, https://doi.org/10.5194/wes-5-1-2020, 2020
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We show in the paper that the upscaling of turbines has led to new requirements in simulation of the unsteady aerodynamic forces by the engineering blade element momentum (BEM) model, originally developed for simulation of the aerodynamics of propellers and helicopters. We present a new implementation of the BEM model on a polar grid which can be characterized as an engineering actuator disc model. The aeroelastic load impact of the new BEM implementation is analyzed and quantified.
Eric J. Limacher and David H. Wood
Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2019-93, https://doi.org/10.5194/wes-2019-93, 2019
Revised manuscript accepted for WES
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This paper describes a new analysis of wind turbine thrust based on removing pressure from the equations for the wind flow through a wind turbine rotor. We show that the equation is free from the effects of flow expansion that must accompany the slowing down of the wind through the blades as they extract the kinetic energy. The conditions under which the assumptions used in blade element analysis, which is fundamental for wind turbine aerodynamics, are made clear for the first time.
Maarten Paul van der Laan, Søren Juhl Andersen, and Pierre-Elouan Réthoré
Wind Energ. Sci., 4, 645–651, https://doi.org/10.5194/wes-4-645-2019, https://doi.org/10.5194/wes-4-645-2019, 2019
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Wind farm layouts are designed by simple engineering wake models, which are fast to compute but also include a high uncertainty. Higher-fidelity models, such as Reynolds-averaged Navier–Stokes, can be used to verify optimized wind farm layouts, although the computational costs are high due to the large number of cases that are needed to calculate the annual energy production. This article presents a new wind turbine control method to speed up the high-fidelity simulations by a factor of 2–3.
Freddy J. Madsen, Antonio Pegalajar-Jurado, and Henrik Bredmose
Wind Energ. Sci., 4, 527–547, https://doi.org/10.5194/wes-4-527-2019, https://doi.org/10.5194/wes-4-527-2019, 2019
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This paper presents a comparison study of the simplified model QuLAF (Quick Load Analysis of Floating wind turbines) and FAST for the planar version of various design load cases, in order to investigate how accurate results can be obtained from this simplified model.
The overall analysis shows that QuLAF is generally very good at estimating the bending moment at the tower base and the floater motions, whereas the nacelle acceleration is generally underpredicted.
Vinit V. Dighe, Francesco Avallone, Ozer Igra, and Gerard van Bussel
Wind Energ. Sci., 4, 439–449, https://doi.org/10.5194/wes-4-439-2019, https://doi.org/10.5194/wes-4-439-2019, 2019
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Multi-element ducts are investigated to further improve the aerodynamic performance of ducted wind turbines. CFD simulations are performed for a multi-element duct geometry consisting of a duct and a flap; the goal is to evaluate the effects on the aerodynamic performance of the radial gap length and the deflection angle of the flap. Increasing the radial gap length results in an augmentation of the total thrust generated by the DWT, whereas a larger deflection angle has an opposite effect.
Alexander R. Meyer Forsting, Georg Raimund Pirrung, and Néstor Ramos-García
Wind Energ. Sci., 4, 369–383, https://doi.org/10.5194/wes-4-369-2019, https://doi.org/10.5194/wes-4-369-2019, 2019
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The actuator line was intended as a lifting line technique for CFD applications. In this paper we prove – theoretically and practically – that smearing the forces of the actuator line in the flow domain leads to smeared velocity fields. By combining a near-wake representation of the trailed vorticity with a viscous vortex core model, the missing induction from the smeared velocity is recovered and a lifting line for CFD simulations established.
Maarten Paul van der Laan, Søren Juhl Andersen, Néstor Ramos García, Nikolas Angelou, Georg Raimund Pirrung, Søren Ott, Mikael Sjöholm, Kim Hylling Sørensen, Julio Xavier Vianna Neto, Mark Kelly, Torben Krogh Mikkelsen, and Gunner Christian Larsen
Wind Energ. Sci., 4, 251–271, https://doi.org/10.5194/wes-4-251-2019, https://doi.org/10.5194/wes-4-251-2019, 2019
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Over the past few decades, single-rotor wind turbines have increased in size with the blades being extended toward lengths of 100 m. An alternative upscaling of turbines can be achieved by using multi-rotor wind turbines. In this article, measurements and numerical simulations of a utility-scale four-rotor wind turbine show that rotor interaction leads to increased energy production and faster wake recovery; these findings may allow for the design of wind farms with improved energy production.
Gesine Wanke, Morten Hartvig Hansen, and Torben Juul Larsen
Wind Energ. Sci., 4, 233–250, https://doi.org/10.5194/wes-4-233-2019, https://doi.org/10.5194/wes-4-233-2019, 2019
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In this paper the results of the stability analysis of a free-yawing downwind turbine are shown and the turbine's ability to align the rotor passively with the wind direction is investigated. The results show that a tilt angle causes the equilibrium yaw position of free-yawing downwind to be non-zero. It is shown that an increase in cone angle can stabilize the free-yaw mode significantly, while blade flapwise flexibility will increase the risk of an instability of the free-yaw mode.
Luis A. Martínez-Tossas, Jennifer Annoni, Paul A. Fleming, and Matthew J. Churchfield
Wind Energ. Sci., 4, 127–138, https://doi.org/10.5194/wes-4-127-2019, https://doi.org/10.5194/wes-4-127-2019, 2019
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A new control-oriented model is developed to compute the wake of a wind turbine under yaw. The model uses a simplified version of the Navier–Stokes equation with assumptions. Good agreement is found between the model-proposed and large eddy simulations of a wind turbine in yaw.
Jiangang Wang, Chengyu Wang, Filippo Campagnolo, and Carlo L. Bottasso
Wind Energ. Sci., 4, 71–88, https://doi.org/10.5194/wes-4-71-2019, https://doi.org/10.5194/wes-4-71-2019, 2019
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This paper describes an LES approach for the simulation of wind
turbines and their wakes. The simulation model is used to
develop a complete digital copy of experiments performed with
scaled wind turbines in a boundary layer wind tunnel, including the
passive generation of a sheared turbulent flow. Numerical results
are compared with experimental measurements, with a good overall
matching between the two.
Franz Mühle, Jannik Schottler, Jan Bartl, Romain Futrzynski, Steve Evans, Luca Bernini, Paolo Schito, Martín Draper, Andrés Guggeri, Elektra Kleusberg, Dan S. Henningson, Michael Hölling, Joachim Peinke, Muyiwa S. Adaramola, and Lars Sætran
Wind Energ. Sci., 3, 883–903, https://doi.org/10.5194/wes-3-883-2018, https://doi.org/10.5194/wes-3-883-2018, 2018
Levin Klein, Jonas Gude, Florian Wenz, Thorsten Lutz, and Ewald Krämer
Wind Energ. Sci., 3, 713–728, https://doi.org/10.5194/wes-3-713-2018, https://doi.org/10.5194/wes-3-713-2018, 2018
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To get a better understanding of noise emissions from wind turbines at frequencies far below the audible range, simulations with increasing complexity were conducted. Consistent with the literature, it has been found that acoustic emission is dominated by the noise generated when the rotor blades pass the tower. These specific frequencies are less dominant in the structure-borne emission. Considering aerodynamic forces acting on the tower is important for the correct modeling of emissions.
Antonio Pegalajar-Jurado, Michael Borg, and Henrik Bredmose
Wind Energ. Sci., 3, 693–712, https://doi.org/10.5194/wes-3-693-2018, https://doi.org/10.5194/wes-3-693-2018, 2018
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This paper presents a simplified numerical model to quickly predict motion and loads of floating offshore wind turbines. Hydrodynamic, aerodynamic and mooring loads are extracted from higher-fidelity numerical tools. Without calibration, the model can predict with good accuracy the motions of the system in real wind and wave conditions. Loads at the tower base are estimated with errors between 0.2 % and 11.3 %. The model can simulate between 1300 and 2700 times faster than real time.
Jennie Molinder, Heiner Körnich, Esbjörn Olsson, Hans Bergström, and Anna Sjöblom
Wind Energ. Sci., 3, 667–680, https://doi.org/10.5194/wes-3-667-2018, https://doi.org/10.5194/wes-3-667-2018, 2018
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This study shows that using probabilistic forecasting can improve next-day production forecasts for wind energy in cold climates. Wind turbines can suffer from severe production losses due to icing on the turbine blades. Short-range forecasts including the icing-related production losses are therefore valuable when planning for next-day energy production. Probabilistic forecasting can also provide a likelihood for icing and icing-related production losses.
Georg Raimund Pirrung and Helge Aagaard Madsen
Wind Energ. Sci., 3, 545–551, https://doi.org/10.5194/wes-3-545-2018, https://doi.org/10.5194/wes-3-545-2018, 2018
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A wind turbine sees an overshoot in loading after a step change in pitch angle because the wake takes some time to reach a new equilibrium. The time constants of this dynamic inflow effect are expected to decrease significantly towards the blade tip. This radial dependency has not been found to the expected extent in previous analyses of force measurements from the NASA Ames Phase VI experiment. In the present article the findings from the experiment are explained based on a simple vortex model.
Pascal Weihing, Tim Wegmann, Thorsten Lutz, Ewald Krämer, Timo Kühn, and Andree Altmikus
Wind Energ. Sci., 3, 503–531, https://doi.org/10.5194/wes-3-503-2018, https://doi.org/10.5194/wes-3-503-2018, 2018
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This research poses the question of whether rotor performance can be increased by an optimized design of the nacelle. For this purpose, the main geometrical parameters of the nacelle, such as the diameter, the relative position of the blade and the detailed shape in the junction of the blade, are investigated by means of computational fluid dynamics. By implementing a fairing-type shape in the junction, the detrimental flow separation in the inner part of the rotor could be eliminated.
Annika Länger-Möller
Wind Energ. Sci., 3, 461–474, https://doi.org/10.5194/wes-3-461-2018, https://doi.org/10.5194/wes-3-461-2018, 2018
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The capability of the DLR flow solver to simulate a wind turbine operating in an extreme gust event is presented by propagating the extreme gust through the flow field. The behaviour of the aerodynamic rotor loading and flow characteristics on the rotor blades were evaluated. The long-term perspective is to improve the understanding of the effects of instationary aerodynamics on the wind turbine. This will help to improve wind turbine design methods.
Annette Claudia Klein, Sirko Bartholomay, David Marten, Thorsten Lutz, George Pechlivanoglou, Christian Navid Nayeri, Christian Oliver Paschereit, and Ewald Krämer
Wind Energ. Sci., 3, 439–460, https://doi.org/10.5194/wes-3-439-2018, https://doi.org/10.5194/wes-3-439-2018, 2018
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The paper describes the experimental and numerical investigation of a model wind turbine with a diameter of 3.0 m in a narrow wind tunnel. The objectives of the study are the provision of validation data, the comparison and evaluation of methods of different fidelity, and the assessment of the influence of wind tunnel walls. It turned out that the accordance between the experimental and numerical results is good, but the wind tunnel walls have to be taken into account for the present setup.
David H. Wood
Wind Energ. Sci., 3, 345–352, https://doi.org/10.5194/wes-3-345-2018, https://doi.org/10.5194/wes-3-345-2018, 2018
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The vortices in the wakes of wind turbines are often approximated by short, straight vortex segments, which cannot reproduce the curvature singularity in the induced velocity. They can also have a second error due to the periodicity: the vortices return to close proximity of the point at which the velocity is calculated. The second error is assessed by representing the far wake of a turbine as a row of vortex rings. The error is quantified and a simple correction is developed.
Jan Bartl, Franz Mühle, Jannik Schottler, Lars Sætran, Joachim Peinke, Muyiwa Adaramola, and Michael Hölling
Wind Energ. Sci., 3, 329–343, https://doi.org/10.5194/wes-3-329-2018, https://doi.org/10.5194/wes-3-329-2018, 2018
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Wake steering by yawing a wind turbine offers great potential to increase the wind farm power production. A model scale experiment in a controlled wind tunnel environment has been performed to map the wake flow's complex velocity distribution for different inflow conditions. A non-uniform sheared inflow was observed to affect the wake flow only insignificantly. The level of turbulent velocity fluctuations in the inflow, however, influenced the wake's velocity distribution to a higher degree.
Jakob Mann, Alfredo Peña, Niels Troldborg, and Søren J. Andersen
Wind Energ. Sci., 3, 293–300, https://doi.org/10.5194/wes-3-293-2018, https://doi.org/10.5194/wes-3-293-2018, 2018
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Turbulence is usually assumed to be unmodified by the stagnation occurring in front of a wind turbine rotor. All manufacturers assume this in their dynamic load calculations. If this assumption is not true it might bias the load calculations and the turbines might not be designed optimally. We investigate the assumption with a Doppler lidar measuring forward from the top of the nacelle and find small but systematic changes in the approaching turbulence that depend on the power curve.
Jannik Schottler, Jan Bartl, Franz Mühle, Lars Sætran, Joachim Peinke, and Michael Hölling
Wind Energ. Sci., 3, 257–273, https://doi.org/10.5194/wes-3-257-2018, https://doi.org/10.5194/wes-3-257-2018, 2018
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In this work, the wake flows behind two different model wind turbines were investigated in wind tunnel experiments user laser Doppler anemometry. It was found that the width of the wake flow is significantly dependent on the quantities examined, becoming much wider when taking higher-order statistics into account. This effect is stable against yaw misalignment and thus affects not only wind farm layout optimizations but also the applicability of active wake steering methods.
Nojan Bagheri-Sadeghi, Brian T. Helenbrook, and Kenneth D. Visser
Wind Energ. Sci., 3, 221–229, https://doi.org/10.5194/wes-3-221-2018, https://doi.org/10.5194/wes-3-221-2018, 2018
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Simulations were used to design ducted wind turbines with the objective of either maximizing power per rotor area (PPRA) or maximizing power per duct exit area (PPDA). When PPRA is maximized, any rotor position within the first half of the duct produces approximately the same PPRA. When PPDA is maximized, the optimal position of the rotor is at the rear of duct. In this case, the PPDA exceeds the theoretical power per unit area that can be produced by an open rotor.
Rick Damiani, Scott Dana, Jennifer Annoni, Paul Fleming, Jason Roadman, Jeroen van Dam, and Katherine Dykes
Wind Energ. Sci., 3, 173–189, https://doi.org/10.5194/wes-3-173-2018, https://doi.org/10.5194/wes-3-173-2018, 2018
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The paper discusses load effects on wind turbines operating under misaligned-flow operations, which is part of a strategy to optimize wind-power-plant power production, where upwind turbines can be rotated off the wind axis to redirect their wakes. Analytical simplification, aeroelastic simulations, and field data from an instrumented turbine are compared and interpreted to provide an informed picture on the loads for various components.
Nymfa Noppe, Wout Weijtjens, and Christof Devriendt
Wind Energ. Sci., 3, 139–147, https://doi.org/10.5194/wes-3-139-2018, https://doi.org/10.5194/wes-3-139-2018, 2018
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A reliable load history is crucial for a fatigue assessment of wind turbines. However, installing strain sensors to measure the load history on every wind turbine is not economically feasible. In this paper, a technique is proposed to reconstruct the thrust load history of a wind turbine based on high-frequency SCADA data and a trained neural network. Both simulated and real-world results show the potential of high-frequency SCADA for thrust load reconstruction.
Mads Mølgaard Pedersen, Torben Juul Larsen, Helge Aagaard Madsen, and Søren Juhl Andersen
Wind Energ. Sci., 3, 121–138, https://doi.org/10.5194/wes-3-121-2018, https://doi.org/10.5194/wes-3-121-2018, 2018
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The wind speed measured by a flow sensor mounted on the blade of a wind turbine is disturbed by the turbine. This paper presents a method to obtain the free turbulence inflow by compensating for this disturbance.
The method is tested using numerical simulations and can be used to extract inflow information for accurate aeroelastic load simulations.
Signe Schløer, Laura Garcia Castillo, Morten Fejerskov, Emanuel Stroescu, and Henrik Bredmose
Wind Energ. Sci., 3, 57–73, https://doi.org/10.5194/wes-3-57-2018, https://doi.org/10.5194/wes-3-57-2018, 2018
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A model for quick load analysis is presented. This is a fast model for the calculation of dynamic loads of an offshore wind turbine tower and foundation. The model is compared to the state-of-the-art aeroelastic code. In general, there is good similarity between the two models. This indicates that in the early stage of the design phase a simple dynamic model can be used to make a preliminary design of the foundation and wind turbine tower.
Iván Herráez, Elia Daniele, and J. Gerard Schepers
Wind Energ. Sci., 3, 1–9, https://doi.org/10.5194/wes-3-1-2018, https://doi.org/10.5194/wes-3-1-2018, 2018
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Several methods have been proposed in the past for extracting the blade performance of wind turbines from simulations. In this work, we present a new method that allows obtaining those data easily not only from simulation results but also from flow measurements. We apply the method to both experiments and simulations of a well-known wind turbine model. The results provide insight into the wind turbine aerodynamics and open up new possibilities for the validation of simulation models.
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We present an experimental method for aerodynamic characterization of flexible membrane kites by in situ measurement of the relative flow, while performing complex flight maneuvers. We find that the aerodynamics of this type of wing depend not only on the angle of attack, but also on the level of aerodynamic loading and the aeroelastic deformation. We recommend using the relative power setting of the kite as a secondary influencing parameter.
We present an experimental method for aerodynamic characterization of flexible membrane kites by...
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