bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wind-tunnel experimental study on identification of modal aerodynamic damping matrix for operating wind turbines
Authors: Wang Zhaowei , Chen Chao , Hua Xugang 
Published: June 2024

Abstract
This study aimed to design a scaled wind turbine model, with a geometric scaling factor of 1/75 and based on the NREL-5MW wind turbine prototype, in order to conduct an experimental study on the aerodynamic damping identification under the operating condition. First, the dynamic characteristics of the scaled model such as natural frequency and damping ratio were tested under the parked condition. Then, wind tunnel force measurements were conducted to verify the similarity between the rotor thrust coefficients of the scaled model and prototype, ensuring a reasonable rotor design. Subsequently, identification of the modal aerodynamic damping matrix of the operating scaled wind turbine model was performed using the identification method based on artificial harmonic excitations and frequency response functions. Experimental results show that both the identified diagonal and off-diagonal terms in the modal damping matrix agree well with the theoretical values when the rotor rotation speed is 150 rpm. However, apparent differences between the identified values and theoretical values can be observed when the rotor rotation speed and wind speed change. Generally, the wind tunnel test confirms the availability of the theoretical modal damping matrix expression in capturing the damping characteristics and the feasibility of the identification method for operating wind turbines.
Multivariate prediction on wake-affected wind turbines using graph neural networks
Authors: Santos Francisco de N , Duthé Gregory , Abdallah Imad , Réthoré Pierre-Élouan , Weijtjens Wout , Chatzi Eleni , Devriendt Christof 
Published: June 2024

Abstract
Modern wind turbines are large and slender dynamical structures with a fatigue loading profile of complex nature. The guarantee of their structural integrity is paramount for materializing cost efficient and more reliable wind energy. The measurement of the global dynamic response and loads of wind turbines is fundamental for achieving this goal. However, an industry-wide, cost-effective direct sensing framework is yet to arise. Moreover, deploying physical sensors and measurement systems on every structural component of interest of a wind turbine induces prohibitive costs in deployment, maintenance and data management. Considering that direct fluid-structure interaction simulations on a farm level are not computationally feasible, the preferred path for structural response estimation on wind farms has been surrogate modelling. Within this landscape, new model architectures have risen in recent years which are able to take into account graph structured data (i.e. non-euclidean data). Wind turbines positioned in a farm, where there is a layout- and topology-dependant interplay of aerodynamic wake affecting the loading profile and power production, lend themselves perfectly to this paradigm. Thus, in this contribution, we introduce the use of graph neural networks (GNN) for layout agnostic saptio-temporal joint modelling of fatigue loads effects, rotor-averaged wind speed and power production on individual turbines of wind farms. To this end, we generate stochastic dependent samples of inflow conditions for wind speed, wind direction, wind shear and nacelle yaw angles. Additionally, wind farm layouts are randomly generated based on different geometric shapes (rectangle, triangle, ellipse and sparse circles) with random parametrization (varying orientations, length/width ratio) for different numbers of turbines and minimal distance (based on the rotor diameter). Both the arbitrary layouts and the random inflow conditions are used as inputs for PyWake, a wind farm simulation tool capable of calculating wind farm flow fields, power and fatigue loads. In our analysis, we develop and compare the performance of the GENeralized Aggregation Networks (GEN), the Graph Attention Networks (GAT) and the Graph Isomorphism Network with Edges (GINE) in their accuracy and ability to generalize their joint predictions for unseen layouts, uncertain inflow conditions and fatigue load estimation on the blade root, tower top and tower base of any wind turbine in the farm. Our results indicate that the GEN layer yields the best performance, followed by GINE, while the GAT layer under-performs and is unable to differentiate between different wake conditions. We further observe that the GAT layer causes a latent space collapse, due to the coupled effect of the manner in which we initialise node features and the way in which its messages are computed.
An Autonomous Data Acquisition and System Identification Framework for In-Service Wind Turbine Using p-LSCF Method
Authors: Ozturkoglu Onur , Ozcelik Ozgur , Gunel Serkan , Yurtseven Veysel , Taner Yasar 
Published: June 2024

Abstract
Wind energy has increased its importance among renewable energy sources in recent years due to its high energy production capacity and the return of investment cost in a short time and has become a better alternative to conventional energy sources. The share of relatively large wind turbines in the renewable energy market, which can produce more energy in a short time, is increasing rapidly. Being able to accurately and consistently define the dynamic characteristics of turbines is crucial to ensure that these structures remain operational throughout their economic life and even serve more than their planned lifespan. In this study a novel autonomous data acquisition and system identification framework is developed. The subject of the work is an in-service 2.5 MW horizontal axis wind turbine with three rotor blades in Izmir/Turkey. Vibration, temperature, and relative humidity data is recorded through data acquisition system designed distributed along the turbine tower height (80 m.). Data acquisition system contain three types of sensors at different levels: One tri-axial, three uniaxial accelerometers, temperature, and relative humidity sensors at foundation level; two uniaxial accelerometers at 20-meter level; two uniaxial accelerometers and temperature sensor at 40meter level; two uniaxial accelerometers at 60-meter level; two uniaxial accelerometers, temperature, and relative humidity sensors at 80-meter level. Preprocessed vibration data is transmitted from wind farm to the university campus with operational and environmental data (e.g., wind speed, wind direction, temperature, humidity, rotor speed, nacelle direction, and pitch angle) collecting from turbine SCADA system synchronously. Modal parameters are estimated using p-LSCF method providing more clear stabilization chart than other operational modal analysis methods. A clear stabilization chart makes more easier to choose stable system poles that is significant to automate system identification. Whole data acquisition and system identification process is done without any user interference. A preliminary correlation work is done between the dynamic characteristics of the turbine and operational/environmental factors.
Substructure optimization of a 10MW floating wind turbine for installations in the Mediterranean Sea
Authors: Ferri Giulio , Borri Claudio , Marino Enzo 
Published: June 2024

Abstract
In this contribution, a multi-objective, site-specific optimization procedure aimed at finding the optimal substructure configuration for a 10MW FOWT is presented. An in-house developed Frequency Domain (FD) model is adopted for the simulation of the coupled system. An installation site near to the Italian coastline is selected. The probability distributions of wind speed, significant wave height and peak spectral period are calculated based on a metocean 20-year database of wind and wave records. The multi-objective optimization concerns the joint minimization of the tower structural response under an extreme event and the manufacturing cost of the substructure. Constraints on the admissible platform displacements, cables geometry, and anchor loads are considered. Results show that the optimized solutions significantly reduce the cost of the system with a moderate increase of stresses, opening interesting perspectives for the reduction of the Levelised Cost of Energy (LCOE) in sites characterized by mild sea states and low wind resource.
Validation of an engineering model for vortex generators in a viscous-inviscid interaction method for airfoil analysis
Authors: Sahoo Abhratej , Ferreira Carlos Simao , Ravishankara Akshay Koodly , Schepers Gerard , Yu Wei 
Published: June 2024

Abstract
As the demand for renewable energy increases, wind turbine rotors will become larger with slender blades. Vortex Generators (VGs) are used for passive flow control to avoid flow separation and reduce unsteady loading on the thick root section of slender blades due to their simplicity, inexpensiveness, and the ability to retrofit them to blades. Aerodynamic load calculations for VGs involve long experimental campaigns or resource intensive CFD calculations. Due to their inherent time-intensive nature aeroelastic optimisation and design tools prefer to use simplified but accurate analysis tools for aerodynamic load calculations of clean airfoils. One such class of tools are viscous-inviscid interaction solvers that use Integral Boundary Layer (IBL) methods for viscous calculations in the boundary layer coupled with an inviscid solver for the rest of the domain. The most popular example of this tool is XFOIL. An engineering model for VGs in IBL methods has previously been developed and implemented in XFOIL. In this research, the model parameters are tuned for implementation in another tool RFOIL based on XFOIL. RFOIL has been developed for accurate and robust analysis of wind turbine airfoils with improvements for thick airfoils and rotational corrections. The aerodynamic performance predicted the VG model in both XFOIL and RFOIL is then validated with an extensive database of airfoil data consisting of airfoils between 21% to 60% thickness, as well as Reynolds numbers between 1 million to 14 million, equipped with and without VGs. Finally, the computation time for the VG model is compared with that for a clean airfoil analysis in the same viscous-inviscid interaction solvers RFOIL and XFOIL. The investigation provides an overview of the usability of the engineering model in airfoil design methodologies in the wind turbine industry.
Unsteady aerodynamic modeling of whirl flutter on a bending wing
Authors: Gaudemaris Vincent de , Schotté Jean-Sébastien , Placzek Antoine , Blanc Laurent , Thouverez Fabrice 
Published: June 2024

Abstract
With the new generation of propeller engines, aircrafts become more prone to whirl flutter, an aeroelastic instability possibly causing irreversible structural failures. The prediction of the motion induced aerodynamic loads on the propeller is essential to catch such kind of instability. Classical theory uses a quasi-steady aerodynamic model to obtain analytically the dependence of the forces and moments on the movement. This paper proposes to use an unsteady aerodynamic theory and to take into account the inflow disturbance, to obtain a more realistic model. This leads to a complex dependency of the aerodynamic loads on the vibratory frequency, which is bypassed by the use of a rational matrix approximation (RMA) of the aerodynamic transfer function to obtain a linearized stability problem. Aeroelastic stability studies are performed on a classical two degrees of freedom (dof) structural model, and on another one including one more degree of freedom to represent the wing bending. Results demonstrate a strong dependence of the stability boundaries on the aerodynamic model used, and highlight the precision and convenience of the method involving a RMA of the aerodynamic transfer function. Wing flexibility is of importance, as some unconventional stability boundaries are obtained in comparison to the classical 2-dof model.
A general approach to model human-structure interaction in the case of slender structures
Authors: Vanali M. , Manzoni S. , Berardengo M. , Lucà F. 
Published: June 2024

Abstract
The paper deals with a general approach for modeling human-structure interaction in slender structures. Vertical vibrations are addressed in the paper. The proposed approach relies on the model of the complete system and on a solution procedure capable to account for the most complex dynamic conditions. The effects of changes in pedestrians positions along the structure and of changes in pedestrians postures during motion are combined, therefore taking into account different and time varying mechanical impedances.Moreover, the developed model describes the coupled system (i.e., structure plus people on the structure) through the definition of two different actions of pedestrians: passive and active forces. This approach was used to evaluate the dynamic interactions between a light slender structure and pedestrians. The proposed approach was validated by carrying out experimental tests on a staircase and results show a good match between the predicted vibrations and the experimentally found ones.
Field-testing and serviceability assessment of a lively footbridge
Authors: Mulas Maria Gabriella , Fortis Cristina , Lastrico Giulia 
Published: June 2024

Abstract
Following a previous work, the paper describes the serviceability assessment of a footbridge over the Lambro River near Milano (Italy), based on the comparative analysis of on-field tests and of the outcome of the Hyvoss guidelines. The 3-span footbridge, for a bicycle-pedestrian mixed use, is 107 m long, 4.4 m wide and roughly symmetric about both mid-span and the longitudinal axis. A reinforced concrete (RC) deck is supported by a steel structure: two longitudinal welded I-profiles, braced in their lower part, support the transverse beams that, in turn, support the RC deck. Ambient vibration tests identified the footbridge modal properties, detecting the fundamental bending mode, with the maximum amplitude recorded at mid-span, at 1.75 Hz, well within the critical range of excitation from walking pedestrians. Hence, a series of forced vibration tests was subsequently performed, involving single pedestrians or groups of up to 12 people. Sensors, located as in AVTs, recorded footbridge acceleration, both horizontal and vertical. In all the tests, pedestrians walked in resonance conditions with the first mode frequency along straight trajectories. To excite further the first mode, their spatial configurations were symmetric about the longitudinal axis of the bridge. Difference among tests concerns not only the number of test subjects (TSs), but also their spatial configuration and/or the TSs involved in each test. The comparison among tests sharing similar spatial configurations, with TSs either in a row or in a column, allows a serviceability assessment directly from the experimental footbridge response. The numerical analyses are based on a FE model previously developed, showing an excellent reproduction of the first bending mode, but a poor simulation of the second torsional mode. The outcome of the analyses performed according to HiVoSS guideline is in good agreement with the experimental results, in spite of the very low crowd density of the on-field tests and the unsatisfactory reproduction of the torsional mode within the FE model.
A first step towards the development of load models for the vibration serviceability assessment of footbridges under running actions
Authors: Strobbe Senne , Lottefier Jasper , Broeck Peter Van den , Nimmen Katrien Van 
Published: June 2024

Abstract
The state of the art involving dynamic running actions is limited to single-person load models valid for running on a rigid laboratory floor. Little to no expertise is available on running excitation as a load scenario for civil engineering structures. The development of realistic load scenarios requires input on (1) intra-person variabilities, (2) inter-person variabilities and (3) human-structure interaction phenomena, and their impact on the resulting structural response. This contribution uses vibration measurements on the lower back of running persons to identify and characterize intra- and inter-person variabilities of the dynamic running load. Based on these results, the impact of these variabilities on the resulting structural response is investigated numerically. The results show that as the impact of intra-person variability is negligible, it can be disregarded in design calculations. However, the impact of inter-person variability is shown to be considerable, reducing the resulting structural response with 64% and more. Realistic ranges of inter-person variability should therefore be considered in design calculations.
Extended vibration serviceability assessment of a footbridge that considers the modal coupling
Authors: Bastin T , de Ville de Goyet V , Duchêne Y 
Published: June 2024

Abstract
The evolution of pedestrian bridge design is tending towards increasingly slender and flexible structures which are more sensitive to vibrations caused by pedestrians. The accelerations induced by the dynamic response are checked to fulfil the comfort criteria. The loads proposed in the guides are sinusoidal and harmonic. Since only stationary vibrations are of interest, the system is solved in the frequency domain. The calculation is done in the modal base and the phasing of pedestrian load is associated with each mode to maximise the modal load. Traditionally, engineers calculate for each mode the dynamic peak response with a static analysis using an equivalent resonant loading. Hence, implementing equivalent resonant load could be time-consuming for complex models. Furthermore, this methodology does not consider the cross correlation between the modes that can be enhanced by the presence of Tuned Mass Dampers (TMDs). An automatic load procedure is implemented in our FEM software FinelG which adapts the phasing and surface size of pedestrian loading to obtain the load cases that maximise each modal loading. The dynamic response of the structure for a range of pedestrian walking frequency and phasing corresponding to each eigenmode is solved through an appropriate transfer function matrix. Both methods are compared to the “L’enjambée” footbridge located in Namur, Belgium.
Codifiable probability-based model for footbridges response to random walkers
Authors: Picozzi V , Avossa A M , Ricciardelli F 
Published: June 2024

Abstract
The response to the transient action of a single pedestrian or a small group of pedestrians is required for the serviceability assessment of human-induced footbridge vibrations. The approach adopted by standards and guidelines is proved to lead to a non-uniform level of reliability. This is in contrast with both the stochastic nature of pedestrian gait parameters and the probabilistic approach adopted by modern structural codes. In this paper, firstly the analysis of peak accelerations is developed according to the Eurocode for a number of simply-supported footbridges, both in vertical and lateral directions. These are shown to correspond to different level of probability of exceedance, that is larger for short-span footbridges and smaller for long-span footbridges. Then, a model for the assessment of the characteristic footbridge acceleration is provided. This is based on the prediction of the basic acceleration, i.e. the response of simply-supported footbridges to single pedestrian crossings, and the application of an acceleration ratio factor for footbridge configurations other than simply-supported.
Coupled Flutter Behavior and Mechanism of Flexible Suspended Footbridge
Authors: Lee S H , Hwang Y , Kim H K 
Published: June 2024

Abstract
Flexible suspended footbridges are more prone to flutter than road bridges due to their lightweight, flexible, and slender structural features. Understanding the flutter generation mechanism and developing effective suppression methods are essential for the safe and reliable design of such footbridges. This study conducted complex eigenvalue analysis and wind tunnel tests to investigate the flutter characteristics of a flexible suspended footbridge with a solid deck. The results revealed that the aeroelastic coupling effect between torsional vibration and torsional-driven vertical vibration lead to torsional flutter. The prototype flexible suspended bridge in this paper was constructed by applying open grating to the entire deck to ensure wind stability.
Structure-to-human interaction during rhythmic jumping
Authors: Abraham Nimmy Mariam , Zivanovic Stana , Williams Genevieve 
Published: June 2024

Abstract
Rhythmic jumping is the largest human-induced load that occurs on assembly structures. It involves a repeated alternation between contact and flight phases at a given frequency. Human loading on the structure takes place during the contact phase while the load is zero during the flight phase. When a structure vibrates, the displacement profile of the structure interacts with human movement during the contact phase. This structure-to-human interaction could result in an alteration in the jump height and the contact duration, and thus the peak ground reaction force (GRF) attained. This paper presents an experimental study that investigates the influence of jump timing relative to the platform position in its vibration cycle on rhythmic jumping. The vertical harmonic vibrations of the platform had a magnitude of 2.0 m/s2 and a frequency of 2.8 Hz. Data were collected from a test subject who was instructed to jump at a frequency of 2.8 Hz in such a way as to land at four different instances of the vibration cycle. These were landing on the platform while at its (i) reference position and on the way down (mid-down), (ii) lowest position (trough), (iii) reference position and on the way up (mid-up), and (iv) highest position (peak) in the vibrating cycle. The timings were presented to the test subject through a metronome beat. The peak toe clearance, impact ratio, contact ratio and frequency of jumping were compared on a cycle-by-cycle basis between the four cases of target landing timing as well as on a non-vibrating platform. The impact ratio and the peak toe clearance were positively correlated with each other and negatively correlated with the contact ratio. Furthermore, the jump height and consequently the peak GRF were higher, and the contact ratio was lower for landing at the trough and the mid-up positions, compared to those on the non-vibrating platform. This is the result of the platform helping the test subject to perform jumps of greater impact in case of landing near the trough and the mid-up positions of the platform.
Experimental insight into human footfall loading for walking on vibrating surfaces
Authors: Zhang Sigong , Lin Bintian , Williams Genevieve , Živanović Stana 
Published: June 2024

Abstract
Current design methods for vibration serviceability assessment of pedestrian structures are generally based on footfall loading models representing walking over rigid level surfaces rather than vibrating surfaces that might modify the loading due to human-structure interaction. A two-year project was carried out to identify vertical vibration conditions under which the human-structure interaction occurs. As part of the testing program, participants were asked to walk over either an outdoor footbridge or a rigid ground surface at various step frequencies. Ground reaction forces were measured by using insole sensors, and the effects of vibration amplitudes and walking to vibration frequency ratios on these forces were examined. It was found that the vibrating surface has no discernible effect on the step-to-step variability. Comparison of dynamic load factors generated on the vibrating footbridge with those on the rigid-level ground revealed that while the vibrating surface increased the first dynamic load factor, it actually reduced it when the step frequency approached the fundamental frequency of the structure.