bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Canonical Perturbations in the Inflow on Wind Turbine Loads
Authors: McGhee Jaylon , Wagh Divya , Farnsworth John , Vijayakumar Ganesh 
Published: June 2022

Abstract
The turbulent velocity field in the atmospheric boundary layer creates inflow fluctuations at a wide range of spatial and temporal scales that must be considered for resilient turbine design. This study is focused on separately characterizing the wind turbine’s response to canonical spatial or temporal oscillations in the inflow with only one wavelength or frequency. Temporal fluctuations in the inflow produce a response that is up to an order of magnitude greater than that of purely spatial fluctuations. The response to spatial oscillations in the inflow is also highly dependent on the alignment of the spatial waveform in the inflow to the rotor hub (i.e. phase angle). Different phase angles produced up to a factor of 30 difference in load variations. The integrated wind turbine loads show the largest response to spatial oscillations at wavelengths around 100-140m which is approximately four times the response at the chord scales. Structural deformations largely dampen the response to spatial oscillations in the inflow while increasing the response to temporal fluctuations near the blade rotation frequency. The wind turbine control system also amplifies the load response to temporal oscillations near the blade rotation frequency.
A fast, heuristic method for generating offshore wind farm turbine layouts
Authors: Bech K. H. 
Published: June 2022

Abstract
This paper describes a heuristic method for generating turbine layouts for offshore wind farms, applying a physical analogy between particle motion in a potential field and turbine placement in a wind kinetic energy field. The method is fast, and relies on industry-standard wake models to account for internal and external wake. The method is heuristic in several senses; it is based on physical analogy, it does not solve the wake model explicitly during the iterative process, and it does not necessarily provide an optimal solution at the end of iteration. The current method does not aim to outperform a full optimization with an objective function, explicit wake model solution and an heuristic optimizer algorithm, but the computational speed and simplicity makes it well suited for screening purposes and as initial solutions for more time-consuming methods.
Surrogate modelling of wind fields from point-wise atmospheric turbulence measurements
Authors: Friedrich Jan , Moreno Daniela , Sinhuber Michael , Wächter Matthias , Peinke Joachim 
Published: June 2022

Abstract
We present an advanced model for the generation of synthetic wind fields that can be understood as an extension of the well-known Mann model. In contrast to such Gaussian random field models which control second-order statistics (i.e., velocity correlation tensors or spectra), we demonstrate that our extended model incorporates the effects of higherorder statistics as well. In particular, the empirically observed phenomenon of small-scale intermittency, a key feature of atmospheric turbulent flows, can be reproduced with high accuracy and at considerably low computational cost. Our method is based on a recently developed multipoint statistical description of a turbulent velocity field [J. Friedrich et al., J. Phys. Complex. 2 045006 (2021)] and consists of a superposition of multivariate Gaussian statistics with fluctuating covariances. Furthermore, we explicitly show how such superstatistical Mann fields can be constraint on a certain number of point-wise measurement data. We give an outlook on the relevance of such surrogate wind fields in the context of fatigue loads on wind turbines.
Enhanced resource assessment and atmospheric monitoring of the research wind farm WiValdi
Authors: Wildmann Norman , Hagen Martin , Gerz Thomas 
Published: June 2022

Abstract
Prior to the installation of wind turbines at the Krummendeich research wind farm (referred to as WiValdi) which is developed by the German Aerospace Center (DLR), we conducted measurements with a Doppler wind lidar (DWL) and a microwave radiometer (MWR) for 16 months, starting in November 2020. The remote sensing data was validated against radiosonde measurements in a short-term campaign in September 2021. We present a statistical analysis of wind speed, direction, shear and veer as derived from the DWL as well as static stability from temperature retrievals of the MWR in comparison to model results of the New European Wind Atlas (NEWA). The observational data from 2021 shows a higher occurence rate of winds from northwest in comparison to the longer-term statistics of NEWA (2011-2018). From the overall statistics, cases with the occurence of low-level jets (LLJ) are detected and separated. The LLJs appear in 49% of the observed nights and predominantly in conditions with seaward wind direction. The LLJ increases shear and veer in the rotor swept area and thus the potential loads significantly. Future research at WiValdi will allow to analyse the effects of such load cases on the wind turbines in detail.
Evaluation of two mesoscale wind farm parametrisations with offshore tall masts
Authors: Garcia-Santiago Oscar M. , Badger Jake , Hahmann Andrea N. , Lucia da Costa Graziela 
Published: June 2022

Abstract
We use offshore tall mast measurements in the North and Baltic Sea to evaluate wind farm parametrisations in the Weather Research and Forecasting (WRF) model. We identify periods before and after the construction of neighbouring wind farms around the tall mast for evaluation purposes. We test multiple WRF model set-ups for the pre-construction period to obtain the best configuration representing the region’s wind climate. Our best set-up is then used with the wind farm parametrisations to investigate wind farm wake effects in the post-construction phase. We use two wind farm parametrisation schemes implemented in the WRF model: the Fitch scheme and the Explicit Wake Parametrisation. We select and prioritise cases of low variability in wind speed and direction to isolate the wake effects. Our results indicate an improvement in the wind speed, as a function of height, using both schemes, with the Fitch scheme creating deeper wakes than EWP. Both parametrisations perform well in cases when the mast is aligned far-downwind of the turbines, with mean wind speed differences of less than 0.2 ms−1. In near-wind cases, the performance of the scheme varies with the site. Finally, our research provides a possible baseline for testing the improvements in the wind farms parametrisations schemes in these offshore regions.
Comparison of time averaged wake flow fields between LiDAR measurements and DWM
Authors: Da Costa Louis , Bernard Valentin , Zamanbin Arezoo 
Published: June 2022

AbstractThe Dynamic Wake Meandering model (DWM) promises an accurate way of assessing wake effect through time-resolved simulation of wake flow fields. This study aims to validate the DWM model by comparing 10-minute time averaged wake flow fields to measurements from a LiDAR campaign carried out on the Lillgrund offshore wind farm. An implementation of the DWM model following the parametrization proposed in the IEC61400 standard is used. Two superposition assumptions are tested. Results show a good visual match and relative convergence of a quantitative error metric for downstream distances of 3 to 3.5 turbine diameters. Results in the immediate near wake show a clear mismatch, as expected considering model assumptions. Linear superposition of all wakes performs best, provided that local conditions at the wake emitting turbines are estimated. The present study uses a limited dataset of only one week of LiDAR data, making the results susceptible to measurement uncertainties.
A data-informed analytic model for turbine power prediction with anisotropic local blockage effects
Authors: Juniper Marcus C R , Nishino Takafumi 
Published: June 2022

Abstract
This paper presents a new analytic approach for estimating the local power coefficient of a turbine experiencing anisotropic local blockage effects. Data-driven methods are employed first to approximately obtain a known analytic expression for isotropic local blockage effects, and then deployed to find candidate expressions for anisotropic local blockage effects. The dataset for the analysis of anisotropic local blockage is collected from 3D Reynolds-averaged Navier-Stokes (RANS) simulations of an infinitely wide array of actuator disks for nearly 2,000 different blockage configurations. This study builds upon previous work in array optimisation of both tidal and wind turbines, where the local power coefficient may increase substantially for optimal array configuration. A brief discussion on the relationship between the local blockage and wind farm blockage is also provided. Other theoretical approaches and possible refinements to the presented analytic model are also discussed.
Wake impact of constructing a new offshore wind farm zone on an existing downwind cluster: a case study of the Belgian Princess Elisabeth zone using FLORIS
Authors: Munters Wim , Adiloglu Baris , Buckingham Sophia , Beeck Jeroen van 
Published: June 2022

Abstract
A first assessment of the potential wake impact of the future Princess Elisabeth wind-farm cluster on the existing Belgian wind farms is performed. We consider 3 different wake models coupled to a blockage model implemented in FLORIS, and study 15 design scenarios for the future cluster. Simulations show that, although intra-cluster wake effects are qualitatively comparable, inter-cluster effects differ strongly among model setups, confirming results in recent literature. With increasing new-zone capacity, a trend of higher existing-zone AEP loss caused by the new zone is observed, as well as an incentive to use turbines with higher individual rating. Quantitatively, AEP loss due to inter-cluster wakes can reach up to 0.8% for the full existing zone as compared to a reference case without the Princess Elisabeth zone. Further, worst-case conditions with west-southwesterly winds show the new zone induces an inter-cluster power loss of 6% for the entire existing zone, with extremes up to 20% for specific turbines.
Physics informed DMD for periodic Dynamic Induction Control of Wind Farms
Authors: Muscari C , Schito P , Viré A , Zasso A , van der Hoek D , van Wingerden JW 
Published: June 2022

Abstract
Dynamic Induction Control (DIC) is a novel, exciting branch of Wind Farm Control. It makes use of time-varying control inputs to increase wake mixing, and consequently improve the velocity recovery rate of the flow and the power production of downstream turbines. The Pulse and the Helix are two promising DIC strategies that rely on sinusoidal excitations of the collective pitch and individual pitch of the blades, respectively. While their beneficial effects are evident in simulations and wind tunnel tests, we do not yet fully understand the physics behind them. We perform a systematic analysis of the dynamics of pulsed and helicoidal wakes by applying a data-driven approach to the analysis of data coming from Large Eddy Simulations (LES). Specifically, Dynamic Mode Decomposition (DMD) is used to extract coherent patterns from high-dimensional flow data. The periodicity of the excitation is exploited by adding a novel physics informed step to the algorithm. We then analyze the power spectral density of the resulting DMD modes as a function of the Strouhal number for different pitch excitation frequencies and amplitudes. Finally, we show the evolution in time and space of the dominant modes and comment on the recognizable patterns. By focusing on the modes that contribute the most to the flow dynamics, we gather insight on what causes the increased wake recovery rate in DIC techniques. This knowledge can then be used for the optimization of the signal parameters in complex layouts and conditions.
Design of the American Wake Experiment (AWAKEN) field campaign
Authors: Debnath Mithu , Scholbrock Andy K. , Zalkind Daniel , Moriarty Patrick , Simley Eric , Hamilton Nicholas , Ivanov Chris , Arthur Robert S. , Barthelmie Rebecca , Bodini Nicola , Brewer Alan , Goldberger Lexie , Herges Thomas , Hirth Brian , Valerio Iungo Giacomo , Jager Dave , Kaul Colleen , Klein Petra , Krishnamurthy Raghu , Letizia Stefano , Lundquist Julie K. , Maniaci David , Newsom Rob , Pekour Mikhail , Pryor Sara C , Ritsche Michael T. , Roadman Jason , Schroeder John , Shaw William J. , Van Dam Jeroen , Wharton Sonia 
Published: June 2022

Abstract
The American WAKE experimeNt (AWAKEN) is a multi-institutional collaborative field campaign, starting in March 2022, that will gather an unprecedented data set including both atmospheric observations and wind plant operational data. This comprehensive data set will be used to characterize the wind plant performance and turbine loading in different operational and atmospheric conditions and validate the use of different wind plant control strategies and simulation frameworks. An extensive field campaign like AWAKEN requires proper coordination and long-term planning to be successful. In this paper, we review the major activities planned during AWAKEN to provide information for current and future project partners. Specifically, we provide information about the project sites, their planned instruments, and how these will relate to the scientific objectives of the overall AWAKEN project.
LIDAR based multivariable H∞ feedforward control for load reduction in wind turbines
Authors: Miquelez-Madariaga I. , Schlipf D. , Elso J. , Guo F. , Díaz de Corcuera A. 
Published: June 2022

Abstract
The performance of LIDAR assisted control is highly affected by the quality of the wind measurement. Consequently, it seems convenient to include some kind of uncertainty model during the design of the LIDAR-based feedforward controllers. Robust control methodologies provide a great tool to deal with uncertain systems. In this paper, three H∞ feedforward controllers have been designed based on linear frequency-domain models of the system. Because the control problem is multivariable and multiobjective, the controllers show different combinations of control actions -pitch and generator torque- and control objectives -generator speed regulation and tower base load reduction-. The controllers have been tested in a nonlinear simulation using the aerolastic code OpenFAST, a turbulent wind field and the onshore NREL 5MW wind turbine model.
Aerosense: Long-Range Bluetooth Wireless Sensor Node for Aerodynamic Monitoring on Wind Turbine Blades
Authors: Polonelli Tommaso , Deparday Julien , Müller Hanna , Fischer Raphael , Benini Luca , Barber Sarah , Magno Michele 
Published: June 2022

AbstractPredictive maintenance and structural health monitoring are challenging and promising research fields today. In particular, cost-effective and long-term monitoring of wind turbines has been proven to be one of the key elements to successfully increase their efficiency. Accurate numerical modeling and real-time control-in-the-loop play an increasingly prominent role in understanding and optimizing blade aerodynamic and acoustic performances. A non-intrusive and modular measurement system is a prerequisite for long-term measurement campaigns in existing and future wind turbines. Current methods of performing aerodynamic and acoustic field measurements are cumbersome and expensive, leading to a shortage of aerodynamic and acoustic datasets on operating wind turbines. This paper demonstrates the ability of the new Aerosense system to operate successfully in the field. Aerosense is a long-lasting battery-operated and flexible wireless sensor node that can directly measure aerodynamic and acoustic effects on wind turbine blades. It consists of an array of state-of-the-art Micro-Electro-Mechanical Systems (MEMS) sensors, including 40 barometers and 10 microphones, combined with an ultra low power system-on-chip with wireless transmission over Bluetooth 5.1. Experimental results demonstrate the possibility of continuously acquiring data for up to four months on a single lithium battery of 8.7 Ah, featuring an absolute accuracy of 10Pa and an audio bandwidth of 6kHz.
Spatially distributed and simultaneous wind measurements with a fleet of small quadrotor UAS
Authors: Wetz Tamino , Wildmann Norman 
Published: June 2022

Abstract
The understanding of micro-scale flow in the atmospheric boundary layer is one major challenge in wind energy research. Besides the broad possibilities of numerical simulations, experimental data are necessary for tests of the flow conditions within a wind farm under real conditions. In wind energy and atmospheric science, a variety of measurement devices exist for measuring the wind speed. We propose a measurement system that enables completely flexible simultaneous wind measurements using a fleet of multirotor unmanned aircraft systems (UAS). This approach is validated through a two-week measurement campaign at the boundary layer field site Falkenberg of the German National Meteorological Service (DWD). The wind speed is calculated from UAS motions in hover state without additional wind sensors. The measurements are calibrated and validated against sonic anemometers mounted at a 99 m mast. The capability of highly accurate spatial distributed wind measurement with an improved wind algorithm is proven by a root mean square error (RMSE) of 0.25 ms−1 for the horizontal wind speed and < 5° for the wind direction. Further, turbulence measurements are presented showing valid results up to a frequency of 2 Hz in high turbulence conditions. Additionally, spatially horizontal distributed measurements with multiple UAS are examined in a case study of a gust front event.
Evaluation of the “fan scan” based on three combined nacelle lidars for advanced wind field characterisation
Authors: Meyer P J , Gottschall J 
Published: June 2022

Abstract
Nacelle-mounted lidars are finding more and more applications in the wind industry. Their use cases range from power performance testing to lidar-assisted control. Depending on the application, different wind field parameters are reconstructed from the lidar’s line-of-sight wind measurements. Hereby, the respective scan geometry of the lidar determines the capabilities and limitations for the reconstruction of wind field parameters. In this study, we introduce the fan scan, a scanning pattern made of multiple nacelle-mounted lidars with the aim of an advanced wind field assessment to reconstruct more than three wind field parameters, which has been implemented at the Testfeld BHV site in Bremerhaven, Germany. Analytically derived uncertainties as well as calibration results for both, line-of-sight speeds and reconstructed wind field parameters, are presented indicating a good agreement with reference measurements. Additionally, a method for the reconstruction of the horizontal wind shear is introduced and applied to the fan scan data, highlighting the extended utilization possibilities of nacelle lidars.
Design of a gust generator and comparison of model wind turbine and porous disc wake flows in a transverse gust
Authors: Yigili I. , Andirin M. A. , Akpolat M. T. , Baskan O. , Percin M. , Uzol O. 
Published: June 2022

Abstract
This paper outlines the similarities and differences between the wake characteristics of a porous disc and model wind turbine under transverse gust loading which is generated via a two-vane wind tunnel gust generator. Phase-locked two-dimensional two-component (2D2C) particle image velocimetry (PIV) measurements show that the capability of a porous disc in representing a wind turbine increases under gust loading. Compared to the uniform inflow case, normalized streamwise velocity plots of the porous disc and model turbine are in a better agreement under gusty inflow condition particularly in the near wake region. Comparison of the wake centerlines reveals a similar wavy wake pattern with no significant phase lag suggesting that the gust dynamics is the dominant factor in the determination of the wake dynamics.
Numerical Assessment of a BAY-Type Model for different Vortex Generator Shapes Applied on a Wind Turbine Airfoil
Authors: Seel Ferdinand , Blazejewski Lando , Lutz Thorsten , Krämer Ewald 
Published: June 2022

Abstract
Modern wind turbines are increasingly equipped with vortex generators in the inner part of the rotor blade. On large blades it is usual to install hundreds of these small passive devices to delay flow separation. Therefore, affordable numerical methods to include vortex generators in the design process are required. One very promising method based on the addition of source terms in the flow equations is the BAY model. In this work a BAY-type model is presented and assessed for three different vortex generator shapes (rectangular, delta and cropped-delta) placed on a DU 97-W-300 airfoil and computed with steady-state Reynolds-averaged Navier-Stokes numerical methods. In order to quantify the circulation of the main streamwise vortex, a method to identify the vortex core based on the λ2-criterion is presented and shows good results. The computations reveal very good agreement with the experimental data for attached flow in terms of lift and pressure distribution while drag is inherently underestimated by the BAY model due to the inviscid modelling of the vortex generators. It is displayed that this underestimation is proportional to the vortex generator surface area. Concerning the different shapes, it is shown that the delta shape reveals larger deviations from the fully resolved case than the other geometries and therefore requires higher mesh resolution.
Experimental evaluation of the mesh load factor (Kγ) of a 6MW wind turbine gearbox
Authors: Santiago Unai Gutierrez , Sisón Alfredo Fernández , Polinder Henk , Wingerden Jan-Willem van 
Published: June 2022

Abstract
The significant increase in rotor diameters seen in modern wind turbines has pushed gearbox manufacturers to introduce technological innovations to increase the torque density of current designs. Driven by the need to lower the cost of energy from wind and size limitations imposed by logistic constraints in onshore wind, a trend has emerged to increase the number of planetary stages and the number of planet gears per stage. One of the main challenges of next-generation gearbox designs is sharing the load evenly between a high number of planets. This paper presents an experimental evaluation of the mesh load factor of a modern 6MW wind turbine gearbox with five planets in the first planetary stage. Results from the traditional method, based on tooth root strain gauges, and from strain measurements in the outer surface of the ring gear are described and assessed. Both experimental approaches have yielded lower mesh load factor values than the default values required in the standard “Design requirements for wind turbine gearboxes” IEC 61400-4. Since the mesh load factor is used for gear rating and sizing, a lower value allows a more optimized gearbox design, which leads to a significant improvement in torque density and cost.