bluuebunny/crossref_metadata_2025_split huggingface dataset:
Validation of blade-resolved computational fluid dynamics for a MW-scale turbine rotor in atmospheric flow
Authors: Grinderslev Christian , Vijayakumar Ganesh , Ananthan Shreyas , Sørensen Niels N. , Zahle Frederik , Sprague Michael A. 
Published: September 2020

Abstract
In this study, simulation results of two different computational fluid dynamics codes, Nalu-Wind and EllipSys3D, are presented for a wind turbine rotor in complex yawed and sheared inflow. The results are compared to measurements from the DanAero experiments, to validate computed pressures and azimuthal trends. Despite different code methodologies and grid setups, the codes agree well in computed pressures and integrated forces along the blade for all blade azimuthal positions, however with some discrepancy in the very yawed case. Additionally, both codes capture well the azimuthal trends and force levels seen in measurements. Investigation into discrepancies shows that expanding grids before the rotor, lead to smearing of the wind profiles, which is likely the main cause of the differences in the results between the codes. Additionally, omission of the ground constraint cause discrepancies in relative velocity seen by the passing blade, due to an over speeding beneath the rotor.
The influence of leading edge roughness, rotor control and wind climate on the loss in energy production
Authors: Bak Christian , Forsting Alexander M. , Sorensen Niels N. 
Published: September 2020

Abstract
This study investigates how losses in energy production from wind turbines are influenced by leading edge roughness, rotor control and wind climates using computations. The performance of a NACA633-418 airfoil with five different damage types was predicted using Computational Fluid Dynamics (CFD) with bumps at the leading edge and grooves into the leading edge. Also, one type corresponding to a repair of a leading edge with an “overbite” was investigated. These airfoil characteristics were used in rotor computations where three different wind climates and five different maximum tip speeds were investigated. The rotor computations reflected that the Annual Energy Production (AEP) increased significantly with the average wind speed on the site. They also reflected that the relative AEP losses due to leading edge damages reduced with increasing average wind speed on sites. For the low wind speed site the losses were between 1% and 4% depending on the extent and the type of the blade damage. For the high wind speed site the losses were between 0.5% and 3%. Furthermore, the bigger the extent of the damages were the bigger the losses were. Finally, it was shown that increasing the maximum tip speed increased AEP and decreased the losses.
An experimental and numerical analysis of the dynamic variation of the angle of attack in a vertical-axis wind turbine
Authors: Melani P F , Balduzzi F , Brandetti L , Ferreira CJ Simão , Bianchini A 
Published: September 2020

Abstract
Simulation methods ensuring a level of fidelity higher than that of the ubiquitous Blade Element Momentum theory are increasingly applied to VAWTs, ranging from Lifting-Line methods, to Actuator Line or Computational Fluid Dynamics (CFD). The inherent complexity of these machines, characterised by a continuous variation of the angle of attack during the cycloidal motion of the airfoils and the onset of many related unsteady phenomena, makes nonetheless a correct estimation of the actual aerodynamics extremely difficult. In particular, a better understanding of the actual angle of attack during the motion of a VAWT is pivotal to select the correct airfoil and functioning design conditions. Moving from this background, a high-fidelity unsteady CFD model of a 2-blade H-Darrieus rotor was developed and validated against unique experimental data collected using Particle Image Velocimetry (PIV). In order to reconstruct the AoA variation during one rotor revolution, three different methods-detailed in the study-were then applied to the computed CFD flow fields. The resulting AoA trends were combined with available blade forces data to assess the corresponding lift and drag coefficients over one rotor revolution and correlate them with the most evident flow macro-structures and with the onset of dynamic stall.
Evaluating planetary boundary-layer schemes and large-eddy simulations with measurements from a 250-m meteorological mast
Authors: Peña Alfredo , Hahmann Andrea N. 
Published: September 2020

Abstract
We evaluate the performance of six planetary boundary layer (PBL) schemes and a large-eddy simulation (LES) for the characterization of the neutral PBL through idealized simulations using the Weather Research and Forecasting model. The evaluation is performed by comparison with sonic anemometer measurements from a 250-m tall meteorological tower that observes close-to-homogeneous winds under the predominant westerlies. All simulations show similar behavior for the vertical temperature profile except for one that uses a non-local PBL scheme, which is known to produce excessive vertical mixing. Within the range of measurements of the tower and except for a PBL scheme that produces a too low jet, the simulations using PBL schemes, which were developed to simulate the nighttime atmosphere, generally show the largest deviations from the observed wind speeds. As expected within the surface layer, the LES shows excessive vertical shear. More importantly, we find that two PBL schemes that use their own surface-layer scheme are effectively reducing the surface roughness. When looking at the vertical profile of momentum exchange coefficient, we find very good agreement between a local and a non-local PBL scheme within the bulk of the PBL, the highest values for the simulation with the PBL scheme showing excessive vertical mixing and the lowest values for that most suitable for nighttime conditions. The comparison with the observed turbulent kinetic energy reveals a good match between the LES and a simulation using a local PBL scheme and a general underestimation (overestimation) of turbulence within the range of measurements by the PBL schemes (LES).
Calibration of a super-Gaussian wake model with a focus on near-wake characteristics
Authors: Cathelain M. , Blondel F. , Joulin P.A. , Bozonnet P. 
Published: September 2020

Abstract
Offshore wind turbine near wakes can extend downstream up to 5D due to low atmospheric turbulence intensities. They are characterised by strong velocity deficits, a transitioning Gaussian shape, and strong added turbulence intensities. Classical analytical wake models are still used due to their low computational costs, but they mainly focus on far-wake characteristics. A super-Gaussian wake model valid in near-and far-wake regions has recently been developed at IFP Energies nouvelles. This wake model requires calibration and validation. To this end, large-eddy simulations of the large DTU-10MW reference wind turbine under different neutrally stratified atmospheric flows are carried out with the LES Meso-NH model. A database is generated based on these results and used to calibrate and validate the super-Gaussian model.
Analysing momentum balance over a large wind farm using a numerical weather prediction model
Authors: Lun Ma. , Dunstan Thomas D. , Nishino Takafumi 
Published: September 2020

AbstractThis study attempts to better understand the mechanisms of wind farm blockage effect by analysing momentum balance in realistic atmospheric flow over an idealised large offshore wind farm. The analysis is performed following the two-scale momentum theory, which predicts the importance of three different terms in the farm-scale momentum balance, namely the streamwise pressure gradient, Coriolis force and acceleration/deceleration terms. A numerical weather prediction (NWP) model is used as a realistic farm-scale flow model in this study to investigate how these three terms tend to change in time. Initial results suggest that the streamwise pressure gradient may be enhanced substantially by the resistance caused by the wind farm, whereas its influence on the other two terms appears to be relatively minor. These results suggest the importance of modelling the farm-induced pressure gradient accurately for various weather conditions in future studies of wind farm blockage.
Microscale CFD Simulations of a Wind Energy Test Site in the Swabian Alps with Mesoscale Based Inflow Data
Authors: Letzgus Patrick , Bahlouli Asmae El , Leukauf Daniel , Hofsäß Martin , Lutz Thorsten , Krämer Ewald 
Published: September 2020

Abstract
The current study describes analyses of the WINSENT wind energy test site located in complex terrain in Southern Germany by highly resolved numerical simulations. The resolved atmospheric turbulence is simulated with Delayed Detached Eddy Simulations by the flow solver FLOWer without consideration of the research wind turbines.
The mean inflow and wind direction of the analysed time period is provided by precursor simulations of project partners. The simulation model chain consists of three codes with different time scales and resolutions. The model chain provides a data transfer from mesoscale WRF simulations to OpenFOAM. As a next step OpenFOAM provides inflow data in the valley of the terrain site for the present FLOWer simulations, the code with the highest resolution in space and time. The mean velocity field provided by OpenFOAM is superimposed with fluctuations that are based on measurements to obtain the small turbulent scales within the FLOWer simulations, which the previous tools of the model chain can not resolve. Comparisons with the two already installed met masts clarify that the current FLOWer simulations provide an adequate agreement with measured data. The results are verified with the application of a second simulation, in which a homogeneous velocity profile is superimposed with turbulence. Thus, comparisons with measured data showed that the benefit of using the inflow data of this model chain is especially evident near the ground.
Non-deterministic wind observation from wind turbine loads
Authors: Bertelè M. , Bottasso C.L. 
Published: September 2020

Abstract
In this work, the wind sensing technology that exploits the turbine rotor as an anemometer is further developed into a non-deterministic formulation. First, an inflow-turbine response map is identified, which relates out and in-plane blade root bending moments to both vertical and horizontal shears and misalignments. Then, this linear model is used with and without a Kalman filter to estimate online the wind field at the rotor disk once blade loads are measured. A comprehensive simulation study, including different wind speeds and turbulence intensity levels, was performed to evaluate the accuracy of the new non-deterministic formulation. The results show that introducing a Kalman filter in the estimation process allows for a significant improvement in the angle estimates with respect to the deterministic formulation, with no considerable additional computational cost.
An adaptation of the super-Gaussian wake model for yawed wind turbines
Authors: Blondel Frèdèric , Cathelain Marie , Joulin Pierre-Antoine , Bozonnet Pauline 
Published: September 2020

Abstract
The wake of a yawed wind turbine tends to be deflected and does not follow the incoming wind direction. This phenomenon, often referred to as “wake deflection”, has recently received a lot of attention from the wind energy research community: it is possible to dynamically optimize a wind farm power production by yawing some turbines to deflect their wakes, thus minimizing wake losses over the whole wind farm. In the present work, an analytical model for estimating the deflection of a yawed wind turbine wake is proposed. This new model is based on a super-Gaussian shape assumption for the velocity profile, enabling the estimation of the wake deflection in both near and far wake regions. First, the super-Gaussian model will be briefly introduced. Then, the new wake deflection model will be presented, as well as an updated version of the well known Jimenez model. This revised model allows a proper comparison with the proposed super-Gaussian model, since it is based on a similar definition of the wake width. Finally, results will be compared with experimental data from the literature.
A Graph Neural Network Surrogate Model for the Prediction of Turbine Interaction Loss
Authors: Bleeg James 
Published: September 2020

Abstract
The current generation of wind farm flow models lacks an option that can efficiently and reliably account for both wake and blockage effects when calculating turbine interaction loss. Traditional wake models are fast but ignore blockage effects. High-fidelity flow models are more complete, but turnaround times can be relatively long. The objective of this study is a model that combines the speed of traditional models with the accuracy of higher-fidelity approaches. To this end, we use a graph neural network (GNN) as a surrogate model for a steady-state Reynolds Averaged Navier-Stokes (RANS) model. Comparisons reveal good agreement between the GNN and RANS results for the atmospheric conditions considered.
Large eddy simulation of wind turbine wakes using adaptative mesh refinement
Authors: Zeoli S. , Balarac G. , Bénard P. , Georis G. , Houtin-Mongrolle F. , Bricteux L. 
Published: September 2020

Abstract
The development of turbulent vortical wakes released downstream of wind turbines is a key physical phenomenon as it presents many technological implications for windfarm design and exploitation. The numerical prediction of these wakes constitutes a challenging problem as they involve the shedding of fine vortical structures, their instabilities, and interactions with an ambient turbulent flow. The capture of these complex, three dimensional, unsteady flow phenomena calls for a Large Eddy Simulation (LES) approach. Yet, the computational cost of a scale resolved LES can be huge and the mesh generation process is not obvious when the zones of interest are not known a-priori. Adaptive mesh refinement (AMR) allows generating Eulerian elements only in the regions of interest of the flow, where an action takes place. The AMR strategy proposed here uses the MMG3D library coupled with the YALES2 unstructured finite volume solver. The method is successfully demonstrated on two test cases, the NTNU blind test case for which experimental data exist and the reference NREL 5MW under dynamic yaw conditions.
Influence of turbulence anisotropy on RANS predictions of wind-turbine wakes
Authors: Luan Yuyang , Dwight Richard P. 
Published: September 2020

Abstract
Simulating wind-turbines in Reynolds-averaged Navier-Stokes (RANS) codes is highly challenging, at least partly due to the importance of turbulence anisotropy in the evolution of the wake. We present a preliminary investigation into the role of anisotropy in RANS simulations of vertical-axis turbines, by comparison with LES. Firstly an LES data-set serving as our ground-truth is generated, and verified against previously published works. This data-set provides raw turbulence anisotropy fields for several turbine configurations. This anisotropy is injected into RANS simulations of identical configurations to determine the extent to which it influences (i) the production of turbulence kinetic energy, (ii) the turbulence momentum forcing, and finally (iii) the mean-flow. In all these quantities we observe the anisotropy has a surprisingly limited effect, and is certainly not the leading-order error in Boussinesq RANS for these cases. Nevertheless we go on to show that it is feasible to predict anisotropy fields for unseen configurations based only on the mean-flow, by using a tensorized version of random-forest regression.
Dependence of wind turbine loads on inlet flow field
Authors: Hanssen-Bauer Ø. W. , de Vaal J. B. , Tutkun M. , Asmuth H. , Ivanell S. , Stenbro R. 
Published: September 2020

Abstract
In wind farm simulations, the inflow wind field plays a crucial role in the accuracy of both power production, structural load predictions and the turbulent wake development behind wind turbines. Three different inflow wind field generation techniques, namely the Mann model, a reduced order based model described herein and LES data, are used in this study to characterise the relation between the inflow and the structural response of the wind turbine. In addition, the wake development under different inflow conditions are studied. The turbulence statistics of the reduced-order model and the LES data are similar to each other while the Mann turbulence has different turbulence profiles and spectral characteristics. An in-house developed aeroelastic code, 3Dfloat, is used for structural response analysis. The differences between the inflow fields are mainly attributed to the turbulence intensity profiles, and differences in their spectral characteristics.
Modelling cluster wakes and wind farm blockage
Authors: Nygaard Nicolai Gayle , Steen Søren Trads , Poulsen Lina , Pedersen Jesper Grønnegaard 
Published: September 2020

Abstract
We present two new models for wind turbine interaction effects and a recipe for combining them. The first model is an extension of the Park model, which explicitly incorporates turbulence, both the ambient atmospheric turbulence and the turbulence generated in the wake itself. This Turbulence Optimized Park model is better equipped to describe wake recovery over long distances such as between wind farms, where the wake expansion slows down as the turbine-generated turbulence decays. The second model is a first version of a full engineering wind farm blockage model. In the same vein as the wake model it adds blockage contributions from the individual wind turbines to form an aggregated wind farm scale blockage effect that can be incorporated directly into the park power curve and annual energy calculations. The wake model and the blockage model describe downstream and upstream turbine interaction effects, respectively. They are coupled as the outputs of one model are the inputs to the other model and vice versa. We describe how this coupling is achieved through an iterative process. We give early stage examples of the validation of the two models and discuss how they might be further validated and improved in the future.
Participatory mapping of hydro-meteorological hazard-prone locations
Authors: Sumadio W , Hidayat A , Zubair A , Tampi D M , Lisanyoto L , Fitrinitia I S 
Published: September 2020

Abstract
Community concepts and terms often appear in policies and programs related to environmental issues and community participation. During this time, the concept of community uses the location of residence as the basis for its determination. The assumption is that those who live in these locations are the most familiar with their surroundings. The high displacement of urban residents causes some of them do not always know the place of their residence. This condition can affect the success of development programs that involve the community. To help implementing the program successfully, training on community participation-based map development is needed. The objective of this paper is to offers a way to find out people’s perceptions of where they live, so that they have a collective awareness of their environment through map development. Researchers conducted training of 15 residents who were members of the Kancil community. Kancil community located in a settlement on the edge of Ci Liwung, Depok City, West Java. Data of the environment is collected by mapping the location of a settlement area by several methods. The results of the mapping with the theme of hydro-meteorological disaster sensitivity were integrated subsequently into the form collaborative mapping. This participatory mapping produced a map showing the boundaries of flooded areas, areas prone to clean water scarcity, and locations prone to landslides. Community participation-based map development shows the people’s perception of their environment. Individu with high travel pattern shows knowledge and awareness on their environment. The mental map has a positive influence to their knowledge.
Detection of deforestation and analysis land conversion from high resolution satellite imageries in Bintulu District, Serawak, Malaysia
Authors: Aik D H J , Ismail M H 
Published: September 2020

Abstract
Primary forests are continuously threatened day to day by urbanisation and the conversion to agricultural plantation such as palm oil production and other land uses being one of the major reasons. In South-East Asia, the widespread of oil palm has boomed over the last two decades, resulting in the downfall of tropical forest land. This change has been particularly prevalent in Borneo with protected lands increasingly developed for palm oil and already deforested lands are being converted into industrial plantations. The primary concerns relating to this pattern of land use change are the short and long-term impacts of logging on our natural environments and ecosystems and how patterns of deforestation are contributing to global environment issues such as climate change. By detecting and mapping logging activities, forestry departments are better able to predict land cover changes in a particular region as a result of development and deforestation. In this study, land cover assessment based on remote sensing techniques was used to analyse changes in the Bintulu district, Borneo especially oil palm growth and its influence on the decline of forest areas between 2016 and 2018. High resolution satellite imageries (3 m spatial resolution) from PlanetScope were used due to the benefits in helping to differentiate several land cover classes over a higher spatial resolution. Results showed that a decline of primary forests in Bintulu is about 26.5% over the past 2 years. With that decline, comes a rise of oil palm growth by 17.6% just within 2 years. An increased in logged areas (36.1%) for conversion to other land-covers with a steady decline of other land cover classes by at least 20% each year was detected. The accuracy of results proved a reasonable accuracy with 90.0% confidence with satellite imagery. Thus, with the result a necessary step can be considered to monitor and prevent deforestation and various encroachment in the forest. With high-resolution satellite data, monitoring at local scales has become possible to resource managers as a way to create timely and reliable assessments.
The attractiveness of malls for millennial consumer (Case study: Malls in BSD City)
Authors: Tadiarus N D , Setiadi H , Rizqihandari N 
Published: September 2020

Abstract
Property development, especially malls, continues to make shopping malls in BSD City becoming more diverse. The diversity of these malls is tailored to the needs of various millennial consumers as well. However, the variety of needs based on the diversity of ages and socio-economic status are influenced by motivation and intensity of millennial consumer visits to all malls in BSD. This makes the malls must have attraction to bring millennial consumers to visit. This research aimed to analyze the attractiveness of malls in BSD and the pattern of visits of millennial consumers influenced by the attractiveness of the mall. The variables of this study include location characteristics, concept of the mall and community experience as well as millennial consumer characteristics, motivation to visit the mall and sources of information. The method used in this study is descriptive analysis. The results of the study show that different characteristics of Malls in BSD City make each of them has a different attraction. The difference in attractiveness can influence the pattern of millennial consumer visits related to motivational factors, socio-economic status and sources of information owned by each consumer.