bluuebunny/crossref_metadata_2025_split huggingface dataset:
Overcoming Blade Interference: A Gappy-POD Data Reconstruction Method for Nacelle-Mounted Lidar Measurements
Authors: Kidambi Sekar A. P. , van Dooren M. F. , Kühn M. 
Published: June 2022

Abstract
Nacelle-mounted lidar systems suffer data loss due to unfavourable atmospheric conditions such as rain or fog and most importantly the rotation of the blades that obstruct the laser beam from measuring upstream of the turbine. In this paper, we apply Gappy Proper Orthogonal Decomposition (Gappy-POD) to reconstruct incomplete flow fields from nacelle-mounted lidar measurements. For this purpose, two scanning nacelle-based SpinnerLidar simulations are performed inside a Large Eddy Simulation, one measuring the undisturbed wind inflow and the other in the wake of a reference turbine. Data loss of up to 90 % is simulated by artificially removing measurement points. The performance of Gappy-POD in reconstructing the wind fields is evaluated by comparing metrics such as effective wind speeds, vertical shear, yaw misalignment, wake deficit, wake meandering and the turbulent spectra in fixed and rotating frames of reference. We see that Gappy-POD is capable of accurately reconstructing missing data in comparison to normally used spatial interpolation techniques even in cases where 90 % of the data was missing. As a result, the dynamics of the reconstructed wind fields can be investigated based on highly accurate lidar-based wind field retrievals. The methodology can be used as a tool to develop effective wind field reconstruction techniques from sparse data.
Design and evaluation of rotor blades for fluid structure interaction studies in wind tunnel conditions
Authors: Langidis A , Nietiedt S , Berger F , Kröger L , Petrović V , Wester T T B , Gülker G , Göring M , Rofallski R , Luhmann T , Kühn M 
Published: June 2022

Abstract
Wind tunnel experiments with wind turbine models are a promising method for investigating fluid structure interaction (FSI) phenomena. However, the lack of suitable models that feature properly scaled blades and the complexity of aeroelastic and fluid dynamic measurements during turbine operation is challenging. In this paper, the design methodology for aeroelastically scaled blades which are intended for Model Wind Turbine Oldenburg (MoWiTO) 1.8 is presented. The scaling relations are formulated, initiating from the existing turbines’ design. Next, the manufactured blades are equipped on MoWiTO and are subsequently evaluated, during operation under gusty wind fields produced by an active grid. The tip deflection is recorded using an innovative photogrammetry setup. Simulations of an OpenFAST model, which has properties extracted from the scaling formulation, are used as reference. The recorded loads and blade deformations show similar dynamics, compared to the reference. These results prove the design successful, and the capability of measuring FSI phenomena in wind tunnel environment is showcased.
WindsPT e-Science platform for wind measurement campaigns
Authors: Gomes D F , Lopes J C , Palma J M L M , Senra F , Dias S , Coimbra I L 
Published: June 2022

Abstract
Experimental field campaigns for collecting wind data, essential for academic research and the wind energy industry, are non-trivial due to the complex equipment and infrastructure required. This paper reports the latest developments of the WindsPT e-Science platform for planning, executing, and disseminating wind measurement campaign data. Existing e-Science platforms have been developed for more generic domains, preventing them from capturing the details and requirements of the field. Additionally, we propose a protocol for transferring large volumes of data from the in-site devices to our platform, ensuring data replication. With an easy-to-use Web interface, WindsPT promotes collaboration between participants, disseminates results among the stakeholders, publishes metadata, uses DOI, and includes metadata that enables machine-to-machine communication. The platform has multiple sections, with maps, images, and documents, where there is information about the location of the stations, positioning of the sensors, operating dates, photos, technical sheets, calibration documents, among others. The WindsPT platform has been used to host the Perdigão 2017 experimental campaign and proved to be a valuable tool during all the phases of this large field experiment. A new version of WindsPT, designed to be FAIR, host multiple campaigns, and include multiple cross-campaign shared features, as full-text search capabilities, is now developed and tested.
Wind Tunnel Experiment to Study Aerodynamics and Control of H-Rotor Vertical Axis Wind Turbine
Authors: Jafari M , Sakib M S , Griffith D T , Brownstein I , Strom B , Cooney J 
Published: June 2022

Abstract
This study focuses on wind tunnel testing of a 3-bladed H-rotor vertical axis wind turbine (VAWT) under various conditions. Different performance metrics such as power coefficient (CP
), thrust load coefficient (CX
), and lateral load coefficient (CY
) are presented at four wind speeds. Parked loads, which are key parameters in designing VAWTs, are reported for the baseline case. Apart from presenting the benchmark results for the baseline model, the impact of two control strategies to boost the energy production of the VAWT are investigated. First, the effect of installing the plasma actuators on all blades is tested at four plasma input voltages. The results indicate that plasma actuators are an efficient approach to enhance the aerodynamic efficiency of VAWTs through modification of drag and lift loads acting on the blades. The second control strategy evaluated is intracycle RPM control. In this control method, the rotational speed of the turbine is varied with the azimuthal location of blades at each cycle so that the power production is increased. The results observed for this control strategy encourage further research development to expand the limited knowledge on its application for VAWTs.
POD analysis of the wake dynamics of an offshore floating wind turbine model
Authors: Raibaudo C. , Piquet T. , Schliffke B. , Conan B. , Perret L. 
Published: June 2022

Abstract
The wake dynamics of a floating wind turbine model experiencing realistic surge motion and immersed within a properly scaled atmospheric boundary layer is studied through wind tunnel experiments. The turbine is modelled by a porous disk representing the floating 2MW wind turbine located at the offshore test site in Le Croisic (France). Experiments were conducted in the LHEEA’s atmospheric wind tunnel. A surge motion is imposed on the model, using a linear actuator, to replicate realistic behaviors under wave swell. Realistic frequencies of actuation are considered to study their effects on the wake properties. The wake is characterized using Stereoscopic Particle Image Velocimetry (SPIV) measurements in a y - z plane normal to the flow, at two different streamwise locations x = 4.6D and 8.1D. In addition to the documentation of the main wake statistics, the velocity fields are analyzed using Proper Orthogonal Decomposition (POD). The velocity field is decomposed into a set of spatial and temporal modes. The eigenvalues convergence is shown to be relatively slow, due to the high Reynolds number turbulent boundary layer within which the model is immersed. When varying the surge motion frequency, the spatial modes do not show any significant change in shape and amplitude. However, the spectral analysis performed on the temporal modes shows the emergence of peaks at the surge motion frequency and the overall increase of the low-frequency energy content in the Power Spectral Density, in particular for the highest frequencies of motion tested.
An experimental system to acquire aeroacoustic properties on wind turbine blades
Authors: Deparday J , Müller H , Polonelli T , Barber S 
Published: June 2022

AbstractWind turbine noise is a key issue preventing the successful exploitation of the full potential of wind energy throughout the world, especially in urban areas. To better assess and predict wind turbine noise, several aeroacoustic simulations and models have been developed over the past. Many semi-empirical models for noise emission and propagation rely on aeroacoustic properties at the blade level, including the pressure gradient, the spectrum of the pressure fluctuations, the convection velocity and the coherence lengths. Field measurements of these local quantities on operating wind turbines are valuable to improve the accuracy of the models. In the Aerosense project, a cost-effective smart measurement system is being developed that is thin, easy to install without damaging the blade, low power, self-sustaining and wirelessly transmitting. This measurement system uses MEMS sensors, which require some calibrations and corrections to obtain sufficiently accurate data. This paper describes the experimental system and its workflow, which has been developed within the Aerosense project to obtain sufficiently accurate measurements for semi-empirical noise emission and propagation models. The experimental system and its workflow are then validated in an anechoic wind tunnel on a NACA63-418 airfoil. The results show that this experimental system is able to acquire relevant aeroacoustic properties on operating wind turbines.
A comprehensive procedure to process scanning lidar data for engineering wake model validation
Authors: Hung Lin-Ya , Santos Pedro , Gottschall Julia 
Published: June 2022

Abstract
We propose a comprehensive methodology to incorporate filtering, interpolation and uncertainties estimation in the processing of scanning wind lidar data. A full-scale wake measurement campaign has been carried out at an 8-MW prototype wind turbine in Bremerhaven, Germany, to apply and demonstrate the procedure. The filtering and interpolation of the scanning lidar data results in an average scan that fully covers the turbine rotor swept area. Once the filtered scans are processed, all observations are clustered in a capture matrix, where each bin can be ensemble-averaged according to wind direction, atmospheric stability and turbulence intensity. The final bin-averaged results were compared to an engineering wake model projected onto the lidar’s beam directions, along with an uncertainty model which combines the contributions both from observations and simulation inputs. The results reveal the overall wake characteristics and the ability of the selected model to predict the wake under neutral conditions, with RMSE = 0.532 ms−1. Under stable conditions the model overestimates the wake deficit with greater RMSE = 1.108 ms−1. Nevertheless, we show that this post-processing methodology is effective and can be further applied in other long-range scanning lidar datasets, e.g., for offshore cluster wakes or blockage effect studies.
Contrast enhancement in thermographic flow visualization on wind turbines in operation
Authors: Gleichauf Daniel , Sorg Michael , Fischer Andreas 
Published: June 2022

Abstract
Thermographic flow visualization is a non-contact, non-invasive approach for assessing the aerodynamic state of wind turbine rotor blades and, as a result, the overall efficiency of the wind turbine. The distinguishability between the laminar and turbulent flow regimes in operating wind turbines cannot be easily increased intentionally and is totally dependent on the energy input from the sun. To deal with low-contrast measurement conditions and improve the distinguishability between flow regimes, advanced image processing using the feature extraction method principal component analysis is used. The image processing is applied to an image series of thermographic flow visualizations of a steady flow situation in a free-field experiment on a wind turbine in operation with a low distinguishability between the laminar and turbulent flow regime. The resulting feature images, based on the temporal intensity fluctuations in the images, are evaluated with regard to the global distinguishability between the laminar and turbulent flow regime. By applying the principal component analysis, the contrast-to-noise ratio was increased by a factor of 2.5. Furthermore, the resulting flow visualizations enable a localization of the laminar-turbulent flow transition, that is not possible in the raw data due to missing features in the intensity profile that allow a clear separation.
Wind tunnel study: is turbulent intensity a good candidate to help in bypassing low Reynolds number effects on 2d blade sections?
Authors: Mishra Rishabh , Neunaber Ingrid , Guilmineau Emmanuel , Braud Caroline 
Published: June 2022

Abstract
Wind turbines operate in the turbulent atmospheric boundary layer and can be additionally exposed to the wakes of upstream wind turbines. Hence the inflow encountered by wind turbine rotor blades is turbulent. One way to gain more knowledge on the impact of the turbulence on the airfoil aerodynamics is by studying a 2d airfoil section of a real wind turbine blade against inflows of various turbulence intensities and Reynolds numbers. Therefore, for the purpose of this paper, experiments were performed and aerodynamic coefficients were calculated for chord based Reynolds numbers between 1.3 × 105 and 3 × 105 and angles of attack between -10° and 24° for inflows of three different averaged turbulence intensities, 0.3%, 3% and 5.5%. Results were compared with the already available result of measurements done at a higher chord based Reynolds number of 4.7×106 for the same airfoil type. The results show that, for a given Reynolds number, an increase in turbulence intensity suppresses the flow separation. It was also found that an increase in the turbulence intensity of the inflow does reduce the dependence of aerodynamic coefficients on the Reynolds number. The Comparison between experimental results for lower chord-based Reynolds numbers and high chord-based Reynolds numbers shows differences which implies that an increase of the turbulence intensity is not enough to bypass the low Reynolds number effect completely.
Wind tunnel benchmark tests of airfoils
Authors: Bak Christian , Olsen Anders S. , Fischer Andreas , Lylloff Oliver , Mikkelsen Robert , Gaunaa Mac , Beckerlee Jimmie , Ildvedsen Sigurd , Vronsky Tomas , Grasso Francesco , Loeven Alex , Broersma Liekele , Akay Busra , Madsen Jesper , Hansen Rolf , Kommer Robert 
Published: June 2022

Abstract
This paper describes a benchmark of four airfoils in the Poul la Cour Tunnel (PLCT). The wind tunnel, the corrections used and the method of making adapters for the airfoils are also described. Very good agreement was in general observed between the measurements in PLCT and in other high quality wind tunnels. Some deviations were seen, but they were mainly attributed to the differences in separation on the airfoil. Apart from the benchmarking, this paper also highlights the challenges in testing airfoils in general such as obtaining 2D flow on thick airfoils that inherently shows separated flow and how to make adapters for airfoils tested in other wind tunnels.
Adaptive measuring trajectory for scanning lidars: proof of concept
Authors: Chen Yiyin , Yu Wei , Guo Feng , Cheng Po Wen 
Published: June 2022

Abstract
Application of nacelle-mounted long-range scanning lidars is facing the challenge that the nacelle motion causes deviations in the measuring trajectories. Such lidars are very sensitive to even the slightest trajectory deviation due to its long measuring range. Motivated by this need, we propose the concept of adaptive measuring trajectory and explore its use for eliminating the effect of the rotational motion of the lidar on the target measuring trajectory. This work first aims to experimentally test the performance of adaptive measuring trajectory under ideal conditions by installing a scanning lidar on a 6DOF motion platform to model the lidar motion on the turbine nacelle. The real trajectory with and without correction is measured by a camera. The comparison confirms that the adaptive measuring trajectory could stablize the target measuring trajectory given the lidar motion. Then, the possibility of using Kalman filter to estimate lidar motion given noisy motion measurements is investigated. The results show great potential of Kalman filter for lidar motion estimation, which could be very useful for its future application.
Detection and localization of flow separation on wind turbines by means of unsteady thermographic flow visualization
Authors: Oehme Felix , Sorg Michael , Fischer Andreas 
Published: June 2022

Abstract
For the first time, a thermographic detection and localization of turbulent flow separation on an operating wind turbine is presented and verified. Flow separation on wind turbine rotor blades causes power reduction, structural loads and increased noise emissions. In contrast to established methods for stall detection, the presented infrared thermographic measurement approach is non-invasive, in-process capable and provides a high spatial resolution. With respect to the state of the art for thermographic stall detection in wind tunnel experiments, the thermal surface response to unsteady inflow conditions is evaluated for measurements on an operating wind turbine, in order to achieve unambiguous thermographic features for the detection of flow separation. The evaluation of the thermodynamic response behavior shows a clear detection of flow separation by means of temperature fluctuation maxima in the regions of flow transition as well as an increasing temperature fluctuation within the separated flow region. In addition, a geometric assignment is conducted which enables a localization of the separation point with an uncertainty of 0.6% of the chord length. The detection and localization of flow separation is verified by means of tufts visualization.
Cross validation of the aerodynamic and acoustic measurements in two Kevlar-walled wind tunnels
Authors: Fischer Andreas , Bak Christian , Lylloff Oliver , Olsen Anders S. , Mikkelsen Robert F. , Ildvedsen Sigurd B. , Beckerlee Jimmy S. , Borgoltz Aurelien , Kuester Matthew , Intaratep Nanyaporn 
Published: June 2022

Abstract
The wind tunnel with Kevlar walls is becoming more and more popular for aeroacoustic measurements, because the necessary corrections to convert aerodynamic coefficients to free field values are moderate and at the same time the signal to noise ratio of acoustic measurements are in the same order as in an open jet configuration. Yet, the technology is new and the correction methods for aerodynamic and acoustic coefficients are not well established. This paper aims on bench-marking two of the largest Kevlar-walled wind tunnels by cross validation of the measurements performed on a NACA633018 aerofoil model. The measured aerodynamic coefficients showed and excellent agreement in the attached flow regime. Maximum lift was predicted differently in the two facilities. The differences might be due to three-dimensional effects for separated flow and the fact that the aspect ration was different in the two facilities. The difference of the measured overall sound pressure levels was less ± 1 dB for attached flow conditions. However, we observed a difference in the slope of the sound pressure spectra and recommend to further investigate the acoustic correction methods.
Comparison of different fidelity aerodynamic solvers on the IEA 10 MW turbine including novel tip extension geometries
Authors: Behrens de Luna R , Marten D , Barlas T , Horcas S G , Ramos-García N , Li A , Paschereit C O 
Published: June 2022

Abstract
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.
Structural Design of Wind Turbine Blades with an Additively Manufactured Graded Lattice Core using Topology Optimisation
Authors: Moss A , Macquart T , Panesar A , Forrest M , Greaves P , Pirrera A 
Published: June 2022

Abstract
Conventional wind turbine blade manufacture relies on large, expensive moulds. Instead, using additive manufacturing to print the internal structure of blades, upon which it would be possible to lay composite plies, could significantly reduce manufacturing costs and, as one could “3D print” topologically optimal designs, improve structural efficiency. In general, topology optimisation integrates well with additive manufacturing. There are, however, two main challenges associated with the adoption of topology optimisation in wind blade design, i.e. accounting for: (i) the aeroelastic response of blades; and (ii) the variety of different materials that would be employed, in the composite laminates as well as the printed structure. To address these challenges, the present paper proposes a new multi-step design and optimisation framework relying on the combination of three software. First, a conventional aero-servo-elastic model is used to evaluate blade loads and displacements. Next, a topology optimisation software is used to optimise the blade laminates and core structure. Third, a lattice generator is used to convert the topological optimised “grey” design into an equivalent cellular design that can be printed using additive manufacturing. The full methodology of this design framework and an initial proof-of-concept topology optimisation solution are presented in this paper.