bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental and numerical comparison of aerodynamics for a wind turbine rotor model under turbulent inflow conditions
Authors: Dumanoir M , Leroy A , Guilmineau E , Loyer S , Kourta A 
Published: June 2024

Abstract
Computational prediction of aerodynamics for a two-bladed wind turbine rotor model at the profile, blade, and rotor scale are compared to wind tunnel experimental data. Wind tunnel tests are carried out in the large subsonic wind tunnel at the University of Orleans with an instrumented rotor model to obtain power and thrust coefficients, bending moments and pressure chordwise distributions. A passive uniform turbulence grid is used to obtain a turbulence intensity of 3.8% at the front of the rotor. A k − ω SST unsteady Reynolds-averaged Navier-Stockes (URANS) simulation with the ISIS-CFD flow solver is conducted with a fully resolved rotor, with and without automatic grid refinement. The focus of this study is to examine the prediction capabilities of the simulation for various physical variables. The simulation demonstrates a relatively good prediction of power and thrust coefficients compared with experimental data with a maximum scatter of 8.5%. The prediction of the pressure coefficient distribution at three different radial positions is satisfactory, but shows discrepancies when it comes to accurately predicting flow separation and Reynolds effects.
An aerodynamic digital twin of real-world leading edge erosion: Acquisition, Generation and 3D CFD
Authors: Meyer Forsting A , Olsen AS , Sørensen NN , Fischer A , Markussen CM , Bak C 
Published: June 2024

Abstract
Wind turbine blades face extremely challenging environmental conditions over their operating life-time, that can easily exceed 2 decades. Airborne particles (insects, sand, rain, hail, ice, sea spray etc.) strike the blade leading edge (LE) first and erode or attach to it, roughening its surface. Leading edge roughness (LER) can critically alter the aerodynamic performance of blades, as its aerodynamic impact is strongly coupled to its height with respect to the local boundary layer thickness, which is thinnest around the LE. The actual, detailed topographic manifestation of LER on in-service blades—needed to accurately assess its aerodynamic impact—is highly probabilistic, as it depends on the interaction of multiple stochastic parameters, like the environmental conditions, material composition and production process. Yet little high-resolution topographic LER data of this kind is currently available. This paper details how such data is collected from blades of different turbine manufacturers and processed consistently to build digital twins of the measured LER, that can be analysed aerodynamically using 3D CFD or wind tunnels. Here a special focus lies on how to reconstruct the LER topography and build the computational mesh such that the correct aerodynamic response is observed. For this purpose multiresolution signal decomposition is used to process the topographies and a special meshing procedure established.
Automatic detection and correction of aerodynamic imbalances: a noise-based approach
Authors: Sucameli C R , Bertelè M , Bottasso C L 
Published: June 2024

Abstract
This paper proposes the use of noise emissions to identify and rectify aerodynamic imbalances. The approach leverages the fact that a pitch imbalance changes the angle of attack at the blade sections, which in turn results in a change in noise emissions. Simulations performed on a 3.35 MW wind turbine show that aerodynamic imbalances significantly affect the Overall Sound Pressure Level at the 1P rotor frequency, more so than mass imbalances, and this effect is furthermore dependent on the microphone placement around the turbine.
The rebalancing algorithm is tested through simulations in various scenarios, including both single and multiple concurrent blade imbalances, under different wind speeds and turbulence conditions. The algorithm successfully minimizes aerodynamic imbalances in most cases.
Aerodynamic conditions measured at a rotor blade of large wind turbine prototype
Authors: Wegner Anna , Mechler Sebastian , Höning Leo , Denecke Nora , Stoevesandt Bernhard 
Published: June 2024

AbstractIn this paper we present high resolution pressure distributions measured on the surface of a rotor blade of an 8 MW offshore prototype. We investigate two time intervals of approximately 10 minute duration acquired in April 2022. During the first time interval the turbine is operated at rated power, during the second time interval the turbine is operated below rated power. We see a clear increase and decrease of pressure values on the pressure side and suction side of the rotor blade, respectively. Also, 1P frequency oscillations are found in all sensors except during idling state. We find a decreasing signal to noise ratio in these oscillations with increasing distance from leading edge towards trailing edge, indicating higher turbulence in the air flow. Additionally, pressure changes during pitching movements can be observed. These data present the first data set of pressure distribution measured over a longer time period on a state-of-the-art sized offshore wind turbine prototype and therefore, provide important input for model validation and further understanding of the aerodynamic conditions at a rotor blade.
Velocity-field based load estimation of an unsteady actuator disc
Authors: Yu Wei , Ferreira Carlos Simao 
Published: June 2024

Abstract
Traditional methods for determining the load of an object in unsteady cases, such as Control-volume Momentum Integration (CMI) and Noca methods, encounter challenges related to near-body acceleration and pressure estimation. This prompts the need for innovative techniques to overcome these limitations. This study introduces a novel vorticity-based approach to expand classical load determination methods. The numerical results of an unsteady actuator disc (AD) CFD simulation are used to verify and quantify the uncertainty of the three methods. In the AD model, the load is prescribed and used as a source term. The velocity and pressure fields are solved from the Navier-Stokes equations using the open-source CFD package OpenFOAM, which offers a robust validation framework. Systematic examination of the robustness and accuracy of the three methods across various load and motion unsteady scenarios reveals that the proposed vorticity-based method excels in steady-state scenarios, exhibiting the highest level of robustness and accuracy. In contrast, the traditional CMI method proves more robust and accurate in pure motion cases. In scenarios involving static and moving AD with load variations, the new vorticity-based method demonstrates superior robustness and accuracy, mainly when moderate vorticity dynamics. Conversely, in cases with increased vorticity dynamics in the wake, the accuracy of the vorticity-based method decreases, with the CMI method showing superiority.
Dynamics of the virtual center of wind pressure: An approach for the estimation of wind turbine loads
Authors: Moreno Daniela , Schubert Carsten , Friedrich Jan , Wächter Matthias , Schwarte Jörg , Pokriefke Gritt , Radons Günter , Peinke Joachim 
Published: June 2024

Abstract
A new stochastic method for the reconstruction of time series of bending moments at the main shaft of a wind turbine is presented. The method is based on the characterization of the dynamics of the virtual center of wind pressure (CoWP). The CoWP, calculated purely from the incoming wind field, provides an approach for correlating the bending moments at the shaft with large-scale turbulent structures of the wind acting on the rotor plane. The proposed method allows a fast procedure for generating time series of loads on the shaft. As a result, the computational and time requirements for maximum and fatigue load assessment could be reduced.
A semi-empirical model for time-domain tower Vortex induced Vibration load simulations of wind turbines
Authors: Arnold M , Filopoulos S , White W , Kamruzzaman M 
Published: June 2024

Abstract
A new method for simulating aeroelastic resonances between vortex shedding and structural eigenfrequencies of a wind turbine tower is presented in this publication. This aero-elastic effect of Vortex induced Vibrations (ViV) has the potential to disrupt installation processes and cause fatigue and extreme loads on the tower. Despite this issue, there are no established simulation methods available in literature, able and sufficiently efficient to predict the ViV in turbulent and site specific design load conditions. This state-of-the-art is extended by introducing an efficient semi-empirical, time-domain simulation method, which is capable of analyzing the tower ViV excitations and aeroelastic responses in wind turbine load simulations of the isolated tower or the full turbine for fatigue and extreme loads. The method is based on an adaptive harmonic equation, which is automatically tuned to the instantaneous tower motions.
Airfoil Icing Prediction with Improved Roughness Model
Authors: Özgen Serkan , Sarıbel Eda Bahar 
Published: June 2024

Abstract
Wind turbines are usually exposed to harsh environmental conditions, resulting in the icing of their structures. The production capability of iced wind turbines drops significantly compared to clean turbines. Understanding how ice build up is the first step in coping with its adverse effects. Analyzing the performance reduction and ice shapes on site can be challenging due to practical difficulties. Numerical analysis of iced blade sections combined with Blade Element Momentum Method can simulate the effects of exposure of wind turbines to icing weather. This paper aims to implement an improved ice accretion model for blade sections of wind turbines. The chosen analytical model is designed to compute roughness due to ice locally and employs three water state models due to icing. Roughness height characterizes the boundary layer development and alters the heat transfer coefficient distribution. The mass balance of the Extended Messinger model that is used for ice accretion prediction is improved by including the remaining water mass on the ice surface. The result of the icing simulation of NACA0012 in wet and dry regimes matches the experimental results well.
A CFD Analysis of Oscillating Airfoil with Leading Edge Roughness: Comparing Correlations for Equivalent Sand Grain Roughness
Authors: Min Seungin , Kim Taeseong 
Published: June 2024

Abstract
Numerical simulations express surface roughness as equivalent sand grain roughness values, so the correlation is required to convert realistic roughness into equivalent sand grain roughness values. The correlations were designed to match the wall velocity distributions for static cases with roughness, and they accurately predicted roughness effects when applied to URANS simulations. Several studies have examined the roughness effect on dynamic pitching airfoils. Still, they have only considered the presence of roughness, neglecting the process of converting the actual roughness to equivalent sand-grain roughness. Thus, in the present study, we apply a static case-based equivalent sand-grain roughness correlation to dynamic pitching analysis to validate the suitability of each correlation and verify the significance of correlation parameters. It was observed from a comparison study between numerical aerodynamic coefficients and experimental data from Ohio State University that physical parameters such as skewness and roughness height were important parameters to predict the dynamic stall behaviour more accurately. It was also observed that dynamic stall prediction accuracy is affected by the frequency and type of airfoil, and through this, it was confirmed that there are additional factors to consider when using an equivalent sand grain roughness correlation on pitching airfoils.
Experimental comparison of a NACA0021 airfoil in large plunging and surging motions at 90
◦
angle of attack
Authors: Xu Guanqun , Yu Wei , Ferreira Carlos , Sciacchitano Andrea , Iyer Sowmya 
Published: June 2024

Abstract
The topic of vortex-induced vibrations on a wind turbine blade has recently gained much attention due to its growing size and flexibility. To address this concern, a wind tunnel test was conducted to study the forced plunging and surging motion of a NACA0021 airfoil at 90° angle of attack. Results indicate that vortex lock-in occurred for a motion amplitude of one chord length even for a small frequency ratio (between motion frequency and static Strouhal frequency) of 0.39. Analysis of the drag coefficient, derived from the phase-averaged Particle Image Velocimetry (PIV) data, shows that a plunging airfoil experiences higher average loading than a surging airfoil, which is deemed to be more harmful considering the higher loading in the crossflow-direction due to the variation of effective angle of attack.
Unbounded Domain Modeling in Axisymmetric Rotor Wake Analysis
Authors: Lokken Thomas , Warncke Norbert , de Tavernier Delphine 
Published: June 2024

Abstract
Mitigating the effects of wind turbine wakes is a central part of wind farm design. This paper proposes a spectral solver for the axisymmetrical Ainslie wake model based on modified Laguerre basis functions over the semi-infinite radial domain and a marching scheme in the downstream direction. This orthogonal basis promises fast convergence and a low number of DOFs for discretizing the continuity and axial momentum equation, promising a computationally efficient method. The numerical implementation of the model could not be finished in time; preliminary results are presented but still show non-negligible conservation errors. The focus of this work lies, therefore, on a detailed derivation of the method and a discussion of the sources of numerical errors in the nonlinear terms, and due to the truncation of the spectral basis, a comparison of the solver outputs to other methods remains part of the ongoing work.
Aeroelastic simulations of the DTU 10 MW turbine using tight coupling integration techniques
Authors: Ntrelia Konstantina , Vandewalle Stefan , Meyers Johan 
Published: June 2024

Abstract
The present study aims to investigate a newly developed multirate time integration technique on aeroelastic simulations of the DTU 10 MW reference wind turbine inside a turbulent atmospheric boundary layer. The turbine is modelled using an actuator line model and a multibody structural solver is employed for the dynamic response. The turbine is studied under cases of laminar flow and a pressure driven boundary layer. Results show that the scheme exhibits high accuracy and matches the theoretical order of the Runge–Kutta scheme. During unsteady operations, substantial deformations were observed that are influenced mainly by the turbine’s rotation and the effect of turbulence in fatigue loading is highlighted.
Impact of rotor blade aerodynamics on tower vortex induced vibration of modern wind turbines
Authors: Ludlam David Vicente , Jacobs Pim , Ahmed Aqeel 
Published: June 2024

Abstract
Modern wind turbines in standstill or idling could experience vortex induced vibrations (VIV); the origin of these vibrations is either shedding from the wind turbine blade referred to as blade VIV or shedding from tower termed as tower (or turbine) VIV. When the whole structure of the wind turbine is considered and the blades are pitched out, the dominant 1st order mode for blade deformation in edgewise direction leads to negligible motion of the tower top, while when the whole turbine vibrates with first tower mode, blades also undergo significant periodic translations and deformations. In this study, forced motion is used to study the impact of aerodynamic damping due to rotor moving with 1st tower mode. In the literature no comprehensive work is available to characterize the impact of blades aerodynamics in the turbine mode either using systematic tests or high-fidelity computational fluid dynamics (CFD). In this article high-fidelity numerical simulations are performed to compute the power injections from the rotor blades when the turbine moves in 1st tower mode. Depending on the inflow angle and the azimuthal position, blades can inject significant power. Thus, the estimated damping from tower-only empirical models could severely underestimate the total aerodynamic power if the power injection from the rotor is neglected.
Investigating 3-D Flow Characteristics of Wind Turbine Airfoils using Delayed Detached Eddy Simulations at High Reynolds Numbers
Authors: Akcengiz Ezgi Orbay , Uzol Nilay Sezer 
Published: June 2024

Abstract
This numerical study investigates the 3-D flow field and aerodynamic characteristics of DU 00-W-212 wind turbine airfoil at high Reynolds numbers. The Computational Fluid Dynamics (CFD) simulations are performed at Reynolds number of 3 million at three different angles of attack for the pre-stall, stall, and post-stall conditions, by using an open source CFD solver SU2. The Delayed Detached Eddy Simulations (DDES) with the Spalart-Allmaras (SA) turbulence model and Langtry-Menter (LM) transition model are performed to address the challenge of predicting unsteady flow characteristics with transition, particularly on the suction side of the airfoil. The 3-D DDES with SA results with and without LM transition model are compared with the 2-D RANS with SA simulations and available experimental data.
Impact of rotor size on the aeroelastic behavior of large turbines: a LES study using flexible actuator lines
Authors: Trigaux François , Chatelain Philippe , Winckelmans Grégoire 
Published: June 2024

Abstract
This paper investigates the impact of rotor size on the structural displacements and loads of large wind turbines during power production. The actuator line method is used in Large Eddy Simulations and is coupled to a structural solver for the blades. The latter consists either of a linear solver based on the Euler-Bernoulli beam theory, or uses BeamDyn to account for the non-linearities. The effects of upscaling are investigated for three reference wind turbines of various sizes: the NREL-5 MW, the DTU-10 MW and the IEA-15 MW. The study reveals that the larger turbines exhibit higher bending relative to the radius and a significant torsion angle. The torsion angle is primarily linked to the structural non-linearities and substantially affects the mean blade loads of the largest turbines. Consequently, the power and thrust coefficients predicted using the linear structural model differ from those obtained using BeamDyn. However, the variations of the root bending moments are predicted similarly using both structural solvers; also suggesting that a linear structural solver is still sufficient for the fatigue analysis. Finally, the fatigue analysis is extended to the shaft loads due to the entire rotor, and empirical scaling trends are derived.
Determination of annual energy production loss due to erosion on wind turbine blades
Authors: Özçakmak Özge Sinem , Bretos David , Méndez Beatriz , Bak Christian 
Published: June 2024

Abstract
Increasing size of the modern wind turbines amplifies the issues of leading-edge erosion, especially on the outboard sections of the blades, impacting both their structural integrity and aerodynamic efficiency. Predicting and detection of the aerodynamic losses which occurs before a noticeable structural degradation on the blade can be crucial for operational predictive maintenance strategies to avoid significant loss production. This paper presents the results from the collaborative study between DTU and CENER in order to investigate the influence of leading-edge erosion on wind turbine aerodynamic performance. For this purpose, three distinct erosion scenarios are analyzed by means of computational fluid dynamics (CFD), both 2D and 3D, blade-element momentum theory (BEM) based solver (OpenFAST) and a Simplified Aerodynamic Loss Tool (SALT). The results from previous studies are used as an input for these tools, with outputs from each tool complementing and reinforcing one another. Furthermore, annual energy production (AEP) reductions due to leading-edge erosion across these tools are compared and validation of the SALT tool is presented. It is observed that the thrust and power losses from both CFD and OpenFAST exhibit comparable results and for a severe erosion case, spanning the last third of the blade, results in a 4.3 % reduction in the annual energy production.
A correction model for the effect of spanwise flow on the viscous force contribution in BEM and Lifting Line methods
Authors: Gaunaa Mac , Sørensen Niels N. , Li Ang 
Published: June 2024

Abstract
Design optimization and aeroelastic load evaluation for wind turbines are still infeasible for CFD due to computational cost. These tasks are carried out using 3D engineering aerodynamic methods, where the local aerodynamic loads are obtained from tabulated 2D aerodynamic polars, which makes the models fast. With recent developments such as highly flexible blades, coned/prebent/swept blades, the relative inflow direction to the “inner” 2D airfoil section systems can have a significant component in the spanwise direction. The Crossflow Principle (CP) is used to treat the effects of this in a physically consistent manner. Cases dominated by pressure forces are described well with the CP method, but it is shown in the paper that CP fails to describe the part of the forces stemming from the friction forces correctly. It is shown in the paper that the power loss due to friction forces will be underestimated with the crossflow principle for rotors with significantly swept blades or other designs with a significant amount of local crossflow on the blades. The present work presents a simple model to correct the baseline crossflow principle method to take into account also the friction force part in a consistent manner. The model is validated with 3D CFD results on a 2D airfoil section. It is shown that the new model successfully corrects for the addition of the viscous forces due to spanwise flow component. The paper includes examples of the effect of using the model on rotor designs with different amounts of blade sweep simulated using a blade element momentum (BEM) and blade element vortex cylinder (BEVC) methods.
Automatically generated state observers – toolchain and validation with real measurements
Authors: Geisler Jens 
Published: June 2024

Abstract
State estimation of wind turbines is the basis for many advanced control strategies and analysis applications such as condition monitoring, fault diagnosis, and much more. It depends on the application and its goals, which states of the real turbine are relevant. Therefore, estimators with different levels of detail and sets of states suitable for the problem at hand are needed. This paper describes a toolchain that generates custom-tailored code for an extended Kalman filter. The aim is to create computationally highly efficient estimators for a wide range of applications. Automatic generation of source code allows for agile experimentation and reduces the risk of time-consuming implementation errors. The new contributions are the selection and combination of all parts of the toolchain, the extension of the integration algorithm to include the Jacobian of the transition function, and the adaptation of an efficient covariance auto-tuning algorithm. Four different models are validated in a three-stage process, including measurement data from a real turbine.