bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of free-stream turbulence on the boundary layer stability of a wind turbine airfoil and near wake
Authors: Fava T C L , Lobo B A , Nogueira P A S , Schaffarczyk A P , Breuer M , Henningson D S , Hanifi A 
Published: May 2023

Abstract
Free-stream turbulence (FST) alters the boundary layer of wind turbine blades, changing the hydrodynamic stability and near wake. Large-eddy simulations (LES) of a blade section with a laminar separation bubble for several turbulence intensities (TI) and a Reynolds number of 105 are performed. The effects of boundary-layer streaks generated by FST on Tollmien-Schlichting (TS) and Kelvin-Helmholtz (KH) instabilities are analyzed with a model based on the parabolized stability equations (PSE). Two competing effects on flow stability are identified. The spanwise-averaged mean-flow distortion stabilizes primary TS/KH modes for increasing TI. However, this contribution seems dominant only for TI ≥ 8.6%. For lower TI, the spanwise-oscillating distortion caused by streaks destabilizes the flow, and the growth rates of secondary modal instabilities increase with the streak amplitude. The destabilization occurs mainly at spanwise locations with negative streaks since the inflection point shifts away from the wall, enhancing inviscid instabilities. Inflection points in the spanwise direction formed by the streaks also contribute to the destabilization. The modal structures from PSE and LES agree. Finally, the trailing-edge near-wake coherent structures are more energetic for TI ≥ 8.6% due to the partial stabilization of modal instabilities, delaying the turbulent breakdown.
On the performance of the helix wind farm control approach in the conventionally neutral atmospheric boundary layer
Authors: Taschner E , van Vondelen AAW , Verzijlbergh R , van Wingerden JW 
Published: May 2023

Abstract
The performance of wind farms can substantially increase when their individual turbines deviate from their own greedy control strategy and instead also take into account downstream turbines operating in the wake. The helix approach is a recently introduced dynamic wind farm control strategy that tackles this issue by leveraging individual pitch control to accelerate wake recovery. Its effective implementation requires detailed knowledge about the scaling between control input and the resulting power gain and turbine loading across the farm. In the present work this scaling is explored by means of large-eddy simulation of a two-turbine farm in the conventionally neutral atmospheric boundary layer. A parameter sweep for the amplitude of the helix is performed showing monotonous increase of the farm’s power output with increasing pitch amplitude within the considered range of zero to six degrees. The scaling of the power gain suggests that a threshold amplitude should be exceeded for effective speed-up of the wake recovery, whereas the damage equivalent loads computed for the turbines indicate an upper limit for the amplitude despite increasing power gains.
Study on the yaw-based wake steering control considering dynamic flow characteristics for wind farm power improvement
Authors: Yu Xin , Liu Yongqian , Chen Tao , Meng Hang , Li Li 
Published: May 2023

Abstract
Wake steering is one of the wind farm control strategies that can effectively reduce wake losses and increase power generation. Upstream wind turbines are set with yaw misalignment angles to deflect their wake away from downstream wind turbines, which will alleviate the wake effect. Currently, the yaw misalignment angles of the wind turbines are optimized through CFD or analytical wake models with a fixed inflow wind direction. However, wind turbines operate in rapidly changing wind directions where they cannot immediately track the optimized yaw misalignment angles owing to the slow yaw mechanism as expected. Therefore, a dynamic yaw control method is proposed in this study with the aim of balancing the energy gain and the number of yaw movements. Firstly, in order to improve efficiency, the yaw misalignment set points of wind turbines are optimized with different wind conditions based on the steady wake model. Then, we illustrate the procedure for determining the yaw misalignment angles for dynamic wind conditions. Finally, the performance of the yaw controller under the measured inflow condition is analyzed for the case of two-turbine array. It was found that the optimized yaw misalignment angles based on the steady model are applied to the dynamic control under changing wind direction, where the energy gain does not reach the estimated value using the static optimized control.
A RANS-based surrogate model for simulating wind turbine interaction
Authors: Criado Risco J. , van der Laan M. P. , Pedersen M. M. , Meyer Forsting A. , Réthoré P.-E. 
Published: May 2023

Abstract
A new wake surrogate model based on Reynolds-averaged Navier-Stokes (RANS) single rotor simulations is presented. The model relies on a series of three-dimensional pre-calculated deficit and added turbulence intensity flow fields, stored in a look-up table (LUT) as a function of the thrust coefficient and the ambient turbulence intensity. For any combination of these parameters, the flow around a wind turbine can be predicted by linearly interpolating within the look-up table. Furthermore, the resulting three-dimensional flow fields from different turbine sources can be superposed linearly to calculate the total wind farm flow. The model is implemented in PyWake and benchmarked against other, commonly employed engineering wake models, namely the Gaussian-Bastankhah, the N. O. Jensen and the Zong models, where RANS wind farm simulations are used as reference. In both full and partial wake cases, the surrogate model achieves a higher accuracy than any other model. Besides providing an accuracy comparable to a full RANS solution, the model can compute a flow case in the order of 1 s on a single processor. The main disadvantage is that the generation of the look-up table is time consuming, computationally expensive and can be memory demanding (especially if more inputs, such as the yaw misalignment angle, stability, etc. are added). Nevertheless, generating the LUT only has to be done once per wind turbine type.
Experimental and numerical study of the wake deflections of scaled vertical axis wind turbine models
Authors: Huang Ming , Sciacchitano Andrea , Ferreira Carlos 
Published: May 2023

Abstract
Wake steering of vertical axis wind turbines (VAWTs) is investigated experimentally and numerically via stereoscopic particle image velocimetry and Reynolds averaged Navier-Stokes simulations. Three different blade pitch angles (-10°, 0°, 10°) of straight H-type VAWTs are adopted to deflect and deform the wake. The experimental results confirm the efficacy of blade pitching on the wake steering, and validate the simulation for both moderate and significant wake deflections. The simulation is then extended to full-scale VAWTs, exploring the wake deflection effects on the power performance of VAWT arrays. The effects of inter-turbine distances and pitching configurations are considered. With the upwind VAWT deflecting the wake, the overall power coefficient is increased by 41%.
RANS simulation of a wind turbine wake in the neutral atmospheric pressure-driven boundary layer
Authors: Baungaard M , van der Laan M P , Wallin S , Abkar M 
Published: May 2023

Abstract
Reynolds-averaged Navier-Stokes (RANS) simulations of a single wind turbine wake in the neutral atmospheric pressure-driven boundary layer (PDBL) are conducted and compared to RANS simulations with inflow based on the more traditional log-law. The latter is valid in the neutral atmospheric surface layer (ASL), while the PDBL is a better representation of the whole atmospheric boundary layer (ABL). It is found that the wake results of the two types of simulations become more similar for increasing ABL height to rotor diameter ratio. In fact, the ASL is shown to be a special asymptotic case of the PDBL. The RANS simulations are also compared to a large-eddy simulation (LES) PDBL case, where it is found that both the ASL and PDBL RANS simulations compare well with the reference LES data in the wake region, while the RANS PDBL compares better with the data in the upper region of the domain.
The effect of the tower’s modeling on the aero-elastic response of the NREL 5 MW wind turbine
Authors: Bernardi Claudio , Della Posta Giacomo , De Palma Pietro , Leonardi Stefano , Bernardoni Federico , Bernardini Matteo , Cherubini Stefania 
Published: May 2023

Abstract
In this work, we aim at evaluating the aeroelastic response of the blades of a standalone NREL 5MW wind turbine by means of a high-fidelity fluid-structure interaction solver based on large-eddy simulation, and compare the results with those of engineering-fidelity methods based on the Blade Element Momentum (BEM) theory. For the latter, we use the software OpenFAST [1], which couples an aerodynamic solver based on the BEM theory with a solver of the blades’ structural dynamics. Concerning the computational fluid dynamics (CFD) solver, the tower and nacelle are modeled by means of an immersed boundary method, whereas the aeroelastic rotor is modeled by an actuator line model coupled with a Computational Structural Dynamics (CSD) solver representing the blades as rotating cantilever beams. A comparison of the CFD-CSD results with the corresponding ones obtained by OpenFAST shows that the predicted displacements at the blade tip remarkably differ between the two approaches in correspondence of the passages of the blades in front of the tower. Indeed, the interaction between the blades and the tower introduces a significant perturbation in the local aerodynamics that leads to a drop of the displacement at the tip of the blade and of the root reaction magnitude, which appear to be not accurately described by OpenFAST.
Large-Eddy Simulations of wind turbine wakes in sheared inflows
Authors: Parinam Anand , Benard Pierre , Terzi Dominic von , Viré Axelle 
Published: May 2023

Abstract
Modern-day wind turbines are growing continuously in size and reach diameters of more than 200m in an effort to meet the fast growing demand for wind energy. As a consequence, the rotors are exposed to larger velocity variations in the approach flow due to the presence of shear, veer and turbulence. The shear of the ambient flow is an important effect that can impact the wake of a turbine twofold: one way is how the wake evolves in the sheared flow; the other way is by impacting the performance and loading of the turbine and, hence, the wake it produces. Both ways can affect the size, shape, spreading and recovery of the turbine wake and, consequently, impact on loads and power output of turbines located downstream. In this study, we analyzed the influence of different inflow wind shear configurations on the evolution of the wake behind the IEA 15MW reference wind turbine by means of high-resolution Large-Eddy Simulations. In order to isolate the shear effects, the mean and hub height wind speed of the inflow was kept constant by prescribing linear shear profiles without turbulence. The influence of Coriolis forces and thermal stratification are neglected. In addition, the effect of the imposed shear on the turbine’s power and thrust, and the effect of including the nacelle in the simulation, were monitored.
Towards the multi-scale Kalman filtering of dynamic wake models: observing turbulent fluctuations and wake meandering
Authors: Braunbehrens R. , Tamaro S. , Bottasso C. L. 
Published: May 2023

Abstract
When dynamic wake models are augmented with a Kalman filter, they can provide dynamic estimates of the turbine inflows. Such estimators –especially when implemented through readily available operational data– can support a variety of practical applications in wind farm operation and monitoring, power forecasting, and others. The present work represents a first step towards a multi-scale approach for the filtering of dynamic wake models, aimed at estimating both small-fast and large-slow scales in the flow. The small-fast scales are caused by flow turbulence, which in turn also causes wake meandering, whereas the large-slow ones represent the propagation of macroscopic changes of ambient conditions (e.g., the passing of a wind direction change front throughout a farm). It is argued that the small-fast-scale problem is more difficult to address, because of the lack of measurements between turbines, and it is therefore the focus of this paper. An ensemble Kalman filter is developed that, based exclusively on power measurements from the turbines, estimates small-fast changes in wind speed and wake position. CFD simulations are used to characterize the performance of the proposed approach. Results indicate that – notwithstanding the lack of measurements of the flow as it travels from one turbine to the other– the filter is still able to provide for reasonable estimates of the inflow at the downstream machine. Additionally, it is shown that the filter typically distinguishes between effects caused by ambient flow changes from those due to wake meandering.
Holistic scan optimization of nacelle-mounted lidars for inflow and wake characterization at the RAAW and AWAKEN field campaigns
Authors: Letizia Stefano , Bodini Nicola , Brugger Peter , Scholbrock Andrew , Hamilton Nicholas , Porté-Agel Fernando , Doubrawa Paula , Moriarty Patrick 
Published: May 2023

Abstract
In this article, we provide a methodological framework for designing the scanning strategies of nacelle-mounted scanning lidars for wind energy field experiments, and apply it at two major experimental field campaigns. For the Rotor Aerodynamics, Aeroelastics, and Wake project (RAAW), we leverage two scanning lidars on one turbine to characterize the incoming turbulence and the turbine wake. For the American WAKE experimeNt (AWAKEN), we use four scanning lidars on top of four turbines in a large wind power plant to investigate both individual wakes and wind-plant-scale flow features.
Stochastic wind farm flow generation using a reduced order model of LES
Authors: Andersen S. J. , Murcia Leon J. P. 
Published: May 2023

Abstract
Large eddy simulations are computationally expensive, which typically limits the simulation time and hence the statistics useful for validation. Here, a reduced order model with a stochastic engine is used to generate stochastic inflow to 48 wind turbines in the Lillgrund wind farm. The stochastic flow realization captures the power production and more importantly the correct cross-correlations in power and blade root flapwise bending moments over the large spatiotemporal region, which the wind farm covers. The analysis show how the cross-correlation increase further into the wind farm, where the highly turbulent flow becomes increasingly self-organized and how the dynamic interaction across the entire wind farm is captured by the first eight modes. Overall, the reduced order model captures the correct dynamics at a fraction of the computational cost, effectively generalizing the LES results beyond a relatively short simulation period.
Implications of complex terrain topography on the performance of a real wind farm
Authors: Bernardoni Federico , Guzman Miguel , Leonardi Stefano 
Published: May 2023

Abstract
Terrain topography affects the atmospheric boundary layer over a vertical region where wind turbines are usually located. It is commonly believed that placing wind turbines on the top of a ridge is beneficial because of the more energetic flow impinging on the turbines. However, the presence of topography with even modest altitude upstream of the wind farm may generate turbulent structures that significantly increase fluctuations in blade loads and power production.
Application of Green’s function in frequency solution for wind turbine blade modelled as box beam
Authors: Wang Jian , Chang Lin , Liu Tingrui 
Published: May 2023

Abstract
In order to study the vibration of composite wind turbine blades, a Green’s function method for frequency calculation is proposed. Based on the variational asymptotic method and Hamilton principle, the mechanical model of wind turbine blade, modelled as box beam with composite laminated structure, is established by using circumferential asymmetric stiffness design. The Green function method is used to analyze the frequency of wind turbine blades from the aspect of ply angle, and the numerical examples are compared with other calculation methods. The results show that the Green function method has good accuracy.
Research on algorithms of system vibration in yaw process of large wind turbine
Authors: Wang Zhiyuan , Wang Jian , Zhao Kang , Ji Zhongwei , Liu Tingrui 
Published: May 2023

Abstract
Aiming at the problem of system vibration during yawing of large wind turbines, the mathematical model is obtained by simulating the structure model of the yawing system, which is then represented by a general free vibration equation. The system vibration equation is modeled and simulated by MATLAB/Simulink. The model is controlled by PID, Fuzzy PID and Optimal Fuzzy PID intelligent algorithm, and the control result is obtained. By comparing the control results between different algorithms, it can be shown that although the PID algorithm and the Fuzzy PID algorithm can obviously and effectively control the vibration model of the yaw system, and the control effect of the Fuzzy PID algorithm is better than that of the PID algorithm, the PID parameters obtained by the “trial and compact method” are not the optimal parameters, which will affect the control effect of the Fuzzy PID. The Optimal Fuzzy PID algorithm can automatically optimize by MATLAB program to obtain the optimal PID parameters and achieve the optimal control effect.
Research on Online Diagnosis of Ship Main Engine with Unbalanced Sample
Authors: Wang Longde , Cao Hui , Wei Lai 
Published: May 2023

Abstract
The traditional ship main engine fault diagnosis model is difficult to update in real time. In addition, the main engine also has the problem of more monitoring parameters and less fault samples. In order to eliminate the influence of the above problems, improve the diagnostic accuracy. Firstly, in order to solve the problem that the traditional diagnosis model is difficult to update online in real time, Online Sequence Extreme Learning Machine is adopted as the diagnosis model, which can update the model directly online by using real-time samples. Then, for the problem that the sample set collected in the online update process is much smaller than the normal sample set, BorderlineSMOTE is used to generate fault samples to balance the sample set, and feature extraction and dimension reduction are carried out in combination with KPCA to further improve the training speed and diagnostic accuracy of the model. Taking the main engine fuel system as an example, the experimental results show that the proposed algorithm has high diagnostic accuracy and good stability, and is suitable for the research of ship main engine fault diagnosis.
Research on the Classification of Inherent Risks of Cranes Based on Interval Laminar Analysis Method-Index Method
Authors: Qi Zuoqiu , Li Mo , Zhao Xiaobing , Li Ronghua , Jiang Lili 
Published: May 2023

Abstract
In order to ensure the safe operation of cranes, from the perspective of the definition of inherent risk, the evaluation index of inherent risk of cranes was established. The interval hierarchy analysis method with better fuzziness was used to determine the index weights, determine the index scores of different levels, and use the integrated index method to establish a grading model, which was divided into four inherent risk levels according to the risk critical value. Application of the model to two cranes for example analysis, the results show that the model has good accuracy. The model provided a more scientific method for grading the inherent risk of cranes, which in turn provided a method of reference for grading the inherent risk of other types of special equipment.
Research on Design Principle and Process Design of Printed Circuit Board Type Overcurrent Protection Device for Chang’e-4 Popular Science Load Cable
Authors: Yang Qingjun , Hu Wenting , Cao Chenlei , Zhang Jin , Hu Jiujiu , Qi Fuqiang 
Published: May 2023

Abstract
The science popularization load of chang’e-4 is a high-density pressure resistant container with a diameter of 173 mm, a height of 198 mm and a weight of only 2.608 kg. It is loaded with cotton, rape, potato, Arabidopsis, yeast and Drosophila. With the successful landing of chang’e-4, this load has entered the growth and development mode of biological lunar surface. The data interface unit (DIU) of the lander provides the primary bus for the science popularization load system of Chang’e 4. The data interface unit provides no overcurrent protection measures for the power supply output. The science popularization load is provided with the command power supply by the lander system unit (SMU). The current limiting resistance of the power supply output is small, and there is moisture inside the science popularization load. In order to cope with the short circuit of the power supply bus and the command bus caused by the unexpected short circuit of the science popularization load power supply connector, In order to ensure the normal operation of popular science load equipment, the overcurrent protection design is considered on the power supply cable of popular science load.
Simulation Study of The Jerk System Based on Multisim
Authors: Lv Ensheng 
Published: May 2023

Abstract
Make an equivalent transformation of the equations of state for a class of Jerk systems, its chaotic dynamics behavior was analyzed. According to the equation of state, the schematic diagram of the chaotic circuit of the Jerk system was designed, and the Jerk circuit was simulated and experimented with Multisim software, and the corresponding two-dimensional phase diagram and time domain waveform diagram appeared, which explained the feasibility of simulating the chaotic circuit with Multisim, and was an effective experimental tool for studying and exploring the chaotic circuit.
A Robust Correlation Filtering Tracker Based on Joint Reliability Evaluation of Target Position Changes
Authors: Han Chao , Li Yixuan , Liu Qingyi , Pang Gang , Ma Xuechun , Fu Yingxia , Bai Peirui 
Published: May 2023

Abstract
Visual tracking is an important branch in computer vision. In complex scenarios, there exist various interference factors, e.g. background clutter, similar objects etc., making robust tracking based on correlation filter algorithm still a challenging task. In this paper, a correlation filter algorithm based on a novel adaptive multi-cue fusion strategy was proposed. First, a unified response map evaluation strategy was presented to assess the tracking reliability by combing the average peak correlation energy and the response peak historical information. Second, according to the cue reliability, an adaptive multi-cue fusion strategy was proposed to adaptively fuse two tracking cues, correlation filter and color histogram. The experimental results on OTB-2013 and UAV123 demonstrated that the proposed algorithm achieved competitive performance to the state-of the-art trackers.