Publications

2023

• Development of a macro-element of foundations under dynamic load : Application in the case of soils reinforced by rigid inclusions
  
  • Shen Yuxiang
  , 2023. The dynamic response of a rigid inclusion-reinforced foundation represents a complex Soil-Structure Interaction (SSI) problem. Considering the limited existing studies, there is a clear necessity to explore the SSI phenomena involved in the response of such foundations under seismic conditions and to enhance the corresponding design methodologies.Building upon insights gained from a limited number of dynamic experimental and numerical studies, this research focuses on the dynamic soil-structure interaction phenomena of foundations reinforced by rigid inclusions. The study aims to provide a better understanding of the seismic behaviour of such foundations using several complementary approaches, including various numerical models, resolution strategies, and analytical analyses. The effects of inertial and kinematic interaction phenomena on the response of both the overall foundation and individual elements within the system (e.g., rigid inclusions, load transfer platform, etc.) are examined in detail.The seismic bearing capacity of foundations reinforced by rigid inclusions is further investigated, using the kinematic exterior approach within the framework of yield design theory. A multi-subsystem analytical approach based on the kinematic exterior approach is introduced and validated through FEM analyses. The evolution of the reduction factors associated with load eccentricity, load inclination, and soil inertia is also explored for several configurations of the reinforcement in terms of coverage area ratio.A novel macro-element for rigid inclusion-reinforced foundations under seismic loading is developed and numerically validated. It allows the modelling of both the linear and non-linear response of the foundation, including uplift, sliding and loss of bearing capacity mechanisms. The validated macro-element model is used to perform a parametric study using a lumped mass model and the Incremental Dynamic Analysis (gls{IDA}) of a 22-storey building, demonstrating the effectiveness and usefulness of the proposed approach in a performance-based design approach.This research is conducted within the framework of the French National project ASIRI+ and French National Research (ANR) project ASIRIplus_SDS.
• Vidange tourbillonnaire : propriétés de l'écoulement et de l'entrainement gazeux
  
  • Caquas Aurore
  , 2023. Un jour, notre regard d’enfant s’est arrêté sur le vortex créé par notre baignoire. D’une apparente simplicité, car il nous semble commun, l’écoulement se caractérise pourtant par une étonnante complexité. La vidange tourbillonnaire fait en effet l’objet de nombreux articles dans la littérature, notamment sur la modélisation du champ de vitesses et du profil caractéristique de l’interface. Pourtant, de nombreuses questions restent ouvertes. Ces études sont souvent menées en régimes stationnaires lorsque le niveau de l’eau est gardé constant par un système de réinjection de l’eau. Le cas instationnaire pour lequel l'eau s'écoule simplement sous l'effet de la gravité est rarement exploré. Nous proposons d’étudier et de comparer ces deux régimes. Les questions abordées portent sur l'influence du vortex sur la loi de Torricelli, les conditions de formation de bulles à la pointe de la déformation de l’interface, ou encore la vitesse de vidange d'une bouteille d'eau idéale mise en rotation.Ces questions qui touchent à notre quotidien ont de forts enjeux industriels : estimation du temps de vidange d’un récipient ou prévention du phénomène d’entrainement de bulles. Ces bulles sont en effet à l’origine de problèmes de sécurité dans les centrales nucléaires et hydrauliques, mais aussi dans bien d'autres systèmes industriels.Notre étude s’intéresse, dans un premier temps, à la modification de l’écoulement de vidange par la présence du vortex et notamment à l’élaboration d’un nouveau modèle pour la vitesse de vidange du récipient. À cet effet, un dispositif à taille humaine a été conçu sur une plateforme-tournante avec un système de mesures embarqué. Le modèle obtenu s'appuie sur la loi classique de Torricelli qu’il est possible de généraliser en prenant en compte l’effet de la déformation de l’interface induite par le vortex. La structure de l’écoulement est aussi fortement impactée par la présence du tourbillon et nous proposons ici d’étudier comparativement les cas de vidanges stationnaire et instationnaire.La forme de l’interface est un problème complexe à modéliser qui dépend des effets de tensions de surface. Sous l’effet d’une vorticité de plus en plus grande et concentrée, cette déformation s’allonge. Le cœur gazeux ainsi formé peut se déstabiliser, osciller et générer des bulles d’air qui seront entraînées dans l’écoulement. Cette thèse propose d’étudier expérimentalement les conditions d’apparitions de cette instabilité.Dans un deuxième temps, notre étude s’intéresse au cas particulier de la vidange d’une bouteille d’eau idéale, i.e. d’une cuve cylindrique hermétiquement fermée, mise en rotation. Nous avons aussi étudié les conditions d’apparition d’un optimum, pour lequel la vidange est réalisée plus rapidement et ainsi tenté de mieux comprendre l’expérience très populaire qui consiste à concevoir un tourbillon dans une bouteille d’eau pour la vider plus vite. En particulier, nous décrivons les différents régimes d’écoulement lors de ce type de vidange, ainsi que les transitions entre ces régimes.Enfin, des simulations numériques basées sur la résolution des équations de Navier-Stokes sont réalisées avec les codes TrioCFD, qui utilise la méthode Front-traking, et OpenFoam, qui utilise la méthode Volume of Fluid et permettent de reproduire certaines expériences de vidange tourbillonnaire. Cependant, le phénomène d’arrachement de bulles par sa finesse reste un défi numérique dont nous aborderons la problématique après une étude comparative des performances des codes utilisés sur différents cas tests de référence.
• Propagation de fissures dans des milieux élastiques avec énergie de surface anisotrope : expériences, simulations de champ de phase et mécanique de la rupture élastique linéaire
  
  • Zhai Xinyuan
  , 2023. La fabrication additive attire une attention croissante en raison de ses avantages en termes de flexibilité de modélisation et de facilité de conception de microstructures complexes. Nous avons constaté qu'en manipulant la stratégie d'impression, les échantillons imprimés par dépôt de fusion de polycarbonate peuvent présenter un comportement fortement anisotrope en termes de résistance à la rupture, tout en conservant des propriétés isotropes en termes d'élasticité.Le focus de cette thèse est d'explorer le comportement en matière de rupture dans des milieux élastiques isotropes présentant une ténacité de rupture anisotrope, en utilisant une combinaison d'investigations expérimentales et de simulations numériques. Dans la partie expérimentale, nous examinons la propagation des fissures dans diverses conditions de chargement en utilisant des géométries d'échantillons variées, englobant à la fois le Mode I et le Mode I+II. Dans la partie numérique, nous adoptons la modélisation de la fissuration fragile par champ de phase basée sur l'approche variationnelle, en utilisant des données expérimentales pour l'étalonnage et l'identification des paramètres numériques. À travers ces méthodologies complètes, notre objectif est de favoriser une compréhension plus profonde de l'interaction entre les motifs d'impression et la sélection des trajectoires de fissures. Cette compréhension a des implications significatives pour guider et gérer la propagation des fissures dans les composants fabriqués par fabrication additive. De plus, nous adoptons les critères classiques basés sur le taux de restitution d'énergie maximale généralisé pour améliorer notre compréhension de la sélection des trajectoires de fissures et de la force critique correspondante.Dans la dernière partie de cette thèse, nous présentons quelques investigations préliminaires concernant l'éventuelle émergence d'un motif de fissure en Zig-Zag dans des spécimens imprimés en 3D. De plus, nous plongeons en profondeur dans le comportement de rupture des spécimens imprimés sous chargement cyclique, offrant une comparaison exhaustive entre les observations expérimentales et les prévisions numériques.
• Identification expérimentale des sources acoustiques à l'origine du bruit de décrochage d'un profil de pale d'éolienne
  
  • Sicard Lisa
  , 2023. Sous l'impulsion de la stratégie nationale bas carbone, le nombre d'implantations d'éoliennes terrestres en France ne cesse d'augmenter depuis 2010. Une des répercussions contrariantes pour l'humain de cette multiplication des éoliennes terrestres est le bruit induit par le fonctionnement des éoliennes. En effet, le bruit éolien représente une gêne sonore se révélant plus incommodante pour les riverains que la pollution acoustique urbaine habituelle telle que le trafic routier ou aérien. Le bruit éolien est communément décrit comme un chuintement facilement détectable et gênant à des niveaux sonores pourtant relativement faibles. Cette caractéristique a été expliquée par la nature particulière de son signal acoustique qui présente des fluctuations temporelles d'intensité. Deux mécanismes aérodynamiques sont à l'origine de cette modulation d'amplitude de bruit : l'interaction des structures turbulentes dans la couche limite des pales avec le bord de fuite de chaque section, générant un bruit appelé bruit de bord de fuite, et le décollement de la couche limite des pales produisant le bruit de décrochage dynamique. Bien que ces phénomènes aient été identifiés, la compréhension du mécanisme à l'origine de la génération de bruit par le décollement de la couche limite reste encore imprécise. Ainsi, dans le cadre du projet ANR PIBE (Prévoir l'Impact du Bruit des Éoliennes) visant à améliorer les méthodes de prévision de l'impact sonore des éoliennes, cette thèse propose d'identifier les structures aérodynamiques à l'origine du bruit de décrochage à la fois en condition statique et dynamique pour un profil aérodynamique de géométrie similaire aux pales d'éoliennes. Dans ce but, deux expériences ont été réalisées au sein de la soufflerie anéchoïque de l'école centrale de Lyon pour un profil NACA633418. Une première expérience de mesures synchronisées de pression pariétales bidimensionnelles à mi-envergure et de microphone en champ lointain a permis de révéler les conditions d'apparition et les caractéristiques spectrales du bruit généré lors du décrochage en condition statique et en condition dynamique lorsque le profil est soumis à un mouvement de tangage sinusoïdal. L'influence de la fréquence et de l'amplitude d'oscillation a également été identifiée. Trois régimes de bruit ont alors été identifiés lors du décrochage statique et quasi-statique : le bruit de séparation, le bruit de décrochage léger et le bruit de décrochage profond. Une seconde expérience de vélocimétrie par imagerie de particules résolue en temps synchronisée avec des mesures acoustiques a ensuite été réalisée afin d'identifier les structures aérodynamiques cohérentes à l'origine de ces bruits. Par le développement d'un protocole d'analyse comprenant l'application d'une méthode de décomposition modale spectrale (SPOD) et le calcul de corrélations croisées entre les mesures aérodynamiques et acoustiques, il a été identifié que le bruit de décrochage profond est induit par la génération et la convection d'un tourbillon de von Kármán de grande échelle. L'analyse en condition dynamique a mis en évidence que le protocole d'analyse présentait des défis supplémentaires nécessitant une investigation approfondie. Néanmoins, les différences entre les caractéristiques aérodynamiques et acoustiques des régimes quasi-statique et dynamique du profil en mouvement de tangage ont tout de même pu être identifiées.
• Nonlinear model order reduction of resonant piezoelectric micro-actuators: An invariant manifold approach
  
  • Opreni Andrea
  • Gobat Giorgio
  • Touzé Cyril
  • Frangi Attilio
  Computers & Structures, Elsevier, 2023, 289, pp.107154. This paper presents a novel derivation of the direct parametrisation method for invariant manifolds able to build simulation-free reduced-order models for nonlinear piezoelectric structures, with a particular emphasis on applications to Micro-Electro-Mechanical-Systems. The constitutive model adopted accounts for the hysteretic and electrostrictive response of the piezoelectric material by resorting to the Landau-Devonshire theory of ferroelectrics. Results are validated with full-order simulations operated with a harmonic balance finite element method to highlight the reliability of the proposed reduction procedure. Numerical results show a remarkable gain in terms of computing time as a result of the dimensionality reduction process over low dimensional invariant sets. Results are also compared with experimental data to highlight the remarkable benefits of the proposed model order reduction technique. (10.1016/j.compstruc.2023.107154)
  DOI : 10.1016/j.compstruc.2023.107154
• Evaluation des efforts d'origine inertielle dans les inclusions rigides
  
  • Shen Yuxiang
  • Pérez-Herreros Jesús
  • Cuira Fahd
  • Semblat Jean-François
  • Burlon Sébastien
  , 2023.
• Etude de la capacité portante des fondations sur inclusions rigides
  
  • Shen Yuxiang
  • Pérez-Herreros Jesús
  • Cuira Fahd
  • Semblat Jean-François
  • Burlon Sébastien
  , 2023.
• On the modeling and numerical simulation of fretting wear
  
  • Caradec Quentin
  , 2023. When two contacting bodies are subjected to fretting motion, namely a cyclic tangential displacement with a very small displacement amplitude, they may experience different forms of degradation. Wear, which is defined as a progressive surface material removal, generally prevails under gross slip conditions. Wear of materials is a very complex phenomenon: it is the long-term, macroscopic result of various microscopic physical and chemical processes. This multi-physical and multi-scale nature makes its modeling difficult, such that there exists no widely adopted unified wear model. The most widespread wear models are empirical, and they sometimes fail to accurately predict wear evolution. As a result, studies on the subject are generally conducted through experimental approaches.The work presented here proposes to tackle the problem through the angle of modeling and numerical simulation. In a first part, an original modeling approach is proposed based on a thermodynamic framework. In this model, wear is accounted for by means of a damage-like variable whose role is to quantify the progressive accumulation of degradation ultimately leading to material detachment. This model uses the thick level set approach to govern the evolution of the surface geometry following wear. A numerical simulation strategy using the finite element method is defined to compute wear evolution using this model.In a second part, focus is on numerical aspects. The numerical simulation of wear problems is especially challenging, on the one hand because it involves several non-linearities (frictional contact, surface geometry evolution, material behavior), and on the other hand because it requires to simulate high amounts of time steps. In order to keep reasonable computational costs, an implicit cycle jump method is implemented. It proves to be more stable and efficient than the usually used explicit method. In addition, a simulation strategy is proposed to integrate the use of elastoplastic material behavior models within the wear simulation frameworks defined.
• Influence of Heat-treatment on Fatigue Properties of Super Duplex 2507 Stainless Steel produced by Directed Energy Deposition Process
  
  • Ballésio Sébastien
  • Szmytka Fabien
  • Dhondt Matthieu
  • Doudard Cédric
  , 2023. Super duplex 2507 (2507 SDSS) is a two-phase austeno-ferritic stainless steel known for its good mechanical properties, especially for fatigue as well as corrosion resistance, due to its mixed microstructure. Metal additive manufacturing, and in particular the Directed Energy Deposition (DED) process, allows the construction or repair of structures for more complex geometries than conventional processes. DED process uses powder that is projected by an argon flow and melted by a laser in the printing area to form the material. This manufacturing protocol however results in different microstructures (grain sizes and orientation, phases repartition) from those observed in conventional processes and particularly forging. The objectives of the study are first to carefully analyse the microstructure of DED-manufactured 2507 SDSS and the effect of different heat treatments on it. Effects on the ratio between austenite and ferrite is particularly discussed. Then, the fatigue limit of this new "material-process" combination is investigated both with Staircase protocols and self-heating tests campaigns. A same grade forged steel is used as reference material. Fatigue limit modelling of DED-manufactured 2507 SDSS is finally performed on the basis of self-heating tests and a dedicated plastic constitutive model.
• Laser powder bed fusion processing of AD730® alloy
  
  • Thomas Marc
  • Hubert Olivier
  • Telmen Baris
  • Szmytka Fabien
  • Solas Denis
  • Locq Didier
  • Morel Ariel
  • Muller Nicolas
  • Tournier Christophe
  , 2023. The Additive Manufacturing (AM) ability of AD730® alloy by laser powder bed fusion (PBF-LB) is investigated for comparison with the cast & wrought AD730® alloy developed by Aubert & Duval for gas turbine applications. Several designs of experiments were needed to identify stable manufacturing conditions and build-up strategy in terms of low defect rate and microstructure soundness. In particular, the laser power, the scan speed, the layers' thickness, the hatching distance, and the scanning strategy were determined to successfully produce crack-free samples. The PBF-LB AD730® alloy exhibits columnar grains along the build direction. The resultant texture is close to a singlecrystalline-like cube texture. Upon annealing (solution annealing + single aging treatment), such a strong texture is preserved despite the formation of a network of fine transgranular secondary g' precipitates. Room temperature tensile properties are encouraging with yield stress lying between the coarse and fine grain microstructures of cast & wrought AD730®, for both orientations. An anisotropic mechanical behavior is obtained with higher properties for specimens printed along X and Y orientations than along Z. Finally, no evidence of premature failure due to micro-cracks has been detected in the overall test specimens.
• A probabilistic study on seismic induced accumulated plastic strain
  
  • Méric Axel
  • Labbé Pierre
  • Boussaa Djaffar
  • Semblat Jean-François
  • Nazé Pierre-Alain
  , 2023, pp.Division 4. A linearization method based on the work of Nguyen [Analyse systématique du concept de comportement linéaire équivalent en ingénierie sismique, PhD., université Paris-Est; EDF; ESTP, Cachan (2017)] is extended in this paper. The method is based on the fitting of the relative acceleration transfer function of a linear SDOF oscillator on non-linear relative acceleration transfer functions to obtain the equivalent dynamic parameters in terms of frequency and viscous damping ratio. This paper proposes formulas for the fitting and introduces an additional parameter in the non-linear transfer function numerical calculation. Elastic perfectly plastic, linear kinematic hardening and non-linear kinematic hardening materials behaviors are considered. The cases of wide and narrow band input motions are explored. The linearization method results are compared to formulas from the literature and evaluated according to goodness of fit criteria. The method gives good results regarding relative speed and acceleration values and less accurate results regarding the maximum displacement prediction. This method should be considered in the case of the determination of transferred motions and fatigue analysis.
• Optimization of plasmonic metasurfaces: a homogenization-based design
  
  • Lebbe Nicolas
  • Pham Kim
  • Maurel Agnes
  Journal of Computational Physics, Elsevier, 2023, 495, pp.112553. This article deals with the optimization of resonant plasmonic metasurfaces through their surface-homogenized counterpart. The derivation of effective transition conditions that takes into account the spatially varying geometries is done using locally periodic surface homogenization. The resulting model reduces the numerical cost of simulating these metasurfaces, thus allowing to find their design using adjoint-based optimization methods. This new algorithm is presented in details, together with various numerical examples to asses its validity and compare its performance with the classical design based on local phase matching. (10.1016/j.jcp.2023.112553)
  DOI : 10.1016/j.jcp.2023.112553
• A ROS-based kinematic calibration tool for serial robots
  
  • Pascal Caroline
  • Chapoutot Alexandre
  • Doaré Olivier
  , 2023. The use of serial robots for industrial and research purposes is often limited by a flawed positioning accuracy, caused by the differences between the robot nominal model, and the real one. Such an issue can be solved by means of kinematic calibration, which are usually tedious and intricate tasks. In this paper, we propose a complete kinematic calibration procedure relying on established geometric modeling, measurements design and parameters identification methods, as well as multiple integration tools, to provide a high adaptability as well as a simplified handling. The overall process was bundled up in a ROS-based modular and user-friendly kinematic calibration package for serial robots, whose main objective is to offer a smooth and fully integrated framework. Our solution was successfully tested using a motion tracking device, and allowed to increase the overall positioning accuracy of two different serial robots by 75% in a matter of hours. (10.1109/IROS55552.2023.10341692)
  DOI : 10.1109/IROS55552.2023.10341692
• Effect of scanning speed on fatigue behavior of 316L stainless steel fabricated by laser powder bed fusion
  
  • Cao Yinfeng
  • Moumni Ziad
  • Zhu Jihong
  • Gu Xiaojun
  • Zhang Yahui
  • Zhai Xingyue
  • Zhang Weihong
  Journal of Materials Processing Technology, Elsevier, 2023, 319, pp.118043. (10.1016/j.jmatprotec.2023.118043)
  DOI : 10.1016/j.jmatprotec.2023.118043
• Size effects in the toughening of brittle materials by heterogeneities: A non-linear analysis of front deformations
  
  • Lebihain Mathias
  • Vasoya Manish
  • Lazarus Véronique
  International Journal of Solids and Structures, Elsevier, 2023, 280, pp.112392. Traditional computational approaches in simulating crack propagation in perfectly brittle materials rely on the estimate of stress intensity factors along the rupture front. This proves highly challenging in 3D when the crack geometry departs from very specific cases for which analytical solutions are available, like e.g. the penny-shaped crack geometry. Here, we extend the first-order theory of Gao and Rice (1987), and predict the distribution of the mode I stress intensity factor KI along the front of a tensile coplanar crack that is slightly perturbed from a reference penny-shaped configuration, up to second order in the perturbation amplitude. Our theory is validated against analytical solutions available for embedded elliptical cracks, and its range of validity is further assessed using numerical simulations performed on cosine front perturbations of varying mode and amplitude. It is then used to develop a homogenization framework for the toughness of weakly disordered media. The effective toughness and its fluctuations are bridged quantitatively to the intensity of the toughness fluctuations and their spatial structure. Our theoretical predictions are compared to the results of ~1 million simulations of crack propagation building on our second-order theory and Fast Fourier Transforms. We show that the impact of toughness heterogeneities is size-dependent, as they generally weaken the material when the crack size is lower or comparable to the typical heterogeneity size, but reinforces it otherwise. It results in an apparent R-curve behavior of the brittle composite at the macroscale. (10.1016/j.ijsolstr.2023.112392)
  DOI : 10.1016/j.ijsolstr.2023.112392
• Damage aassessment in a reinforced concrete structure under quasi-static shear loading using OFDR-based fibre-optic distributed strain monitoring
  
  • Hamdi Ismail
  • Magne Sylvain
  • Rougeault Stephane
  • Mongabure Philippe
  • Vasic Sandra
  • Charbonnel Pierre Etienne
  • Wang Fan
  • Hervé-Secourgeon Estelle
  • Voldoire François
  , 2023. EDF and CEA have established an experimental program to improve knowledge of the behavior of wall-slab junctions under both out-of-plane bending and in-plane shear. The program involved reduced-scale mock-ups made of reinforced concrete (RC) that are representative of the structural elements of nuclear plant buildings. In parallel to vast experimental campaigns, numerical models of the junction under study are derived and calibrated in order to improve the computation of building responses under seismic excitations. The analysis of damaging process of these structures is reproduced by nonlinear numerical simulations, realized within the Finite Element framework CAST3M developed at CEA (www-cast3m.cea.fr/) and code Aster (https://code-aster.org), which account for steel plasticity and concrete damage, including crack propagation based on loading conditions and history. Of all the distributed techniques applicable to the Structural Health Monitoring (SHM) of RC structures, Optical Frequency-Domain Reflectometry (OFDR) is well suited because of its high spatial resolution. The OFDR principle relies on swept-wavelength homodyne interferometry. Light from a tunable laser source is split and sent through sensing and reference fibers, both being arms of an interferometer. The backscattered light recombines at an optical detector and an interferogram is recorded as the laser frequency is tuned. The spectral-domain signal is then Fourier-Transformed to yield the backscattering profile along the fiber. Finally, the fiber is segmented into successive centimeter-long gage lengths and a cross-correlation procedure provides the strain profile with respect to a reference state. We implemented the OBR4600 OFDR device from Luna Innovations. The OBR 4600 is a single channel device that provides static distributed strain monitoring over a range of 70 m, with an accuracy in strain of ±5 µm/m, a spatial resolution (gage length) of about 5 mm, and a readout time of typically 10 seconds. On the last mock-up of the experimental program, the jacks applied quasi-static displacements ranging from 0.69 mm to 11.49 mm, yielding progressive structural damage and eventually reaching concrete crack and steel plasticity. Strain profiles and natural frequencies were determined and compared to the modeling. Distributed Fiber Optic Sensing (DFOS) results provide access to continuous strain distributions along the instrumented rebars, localize deficiencies and local deformations around rebar crossings and also the emergence of concrete degradations in the joint. The OFDR technique enables highly reliable in-situ SHM of damage mechanisms within concrete structures, providing effective data for model verification and validation used in safety-related structures assessment. (10.12783/shm2023/37034)
  DOI : 10.12783/shm2023/37034
• Investigating the Impact of Atmospheric Boundary Layer Stratification on Wind Farm Noise Propagation
  
  • Colas Jules
  • Dragna Didier
  • Emmanuelli Ariane
  • Blanc-Benon Philippe
  • Cotté Benjamin
  • Stevens Richard
  , 2024, pp.4035-4038. <div><p>The expansion of wind farm installations has been hindered by annoyance issues resulting from the noise emitted by wind turbines. Understanding the factors that affect sound propagation is crucial to mitigate the impact of noise. Atmospheric boundary layer (ABL) stratification strongly affects the noise propagation of isolated wind turbines. However, few studies have looked at the influence of atmospheric conditions on wind farm noise propagation. This study aims to investigate this through numerical simulations. Large eddy simulations (LES) are used to predict the mean flow inside and around the wind farm. The noise from each wind turbine is computed from an extended source model that determines the wind turbine sound production based on its geometry, and on the flow characteristics (wind speed and turbulence intensity). A model based on the parabolic equation is employed to compute the sound propagation based on the flow fields obtained from LES. Neutral, stable and unstable stability conditions are considered for an idealized wind farm layout. The results of this study provide insight into the influence of atmospheric conditions on wind farm sound</p></div> (10.61782/fa.2023.0608)
  DOI : 10.61782/fa.2023.0608
• Wind turbine sound propagation: Comparison of a linearized Euler equations model with parabolic equation methods
  
  • Colas Jules
  • Emmanuelli Ariane
  • Dragna Didier
  • Blanc-Benon Philippe
  • Cotté Benjamin
  • J. A. M. Stevens Richard
  Journal of the Acoustical Society of America, Acoustical Society of America, 2023, 154 (3), pp.1413-1426. Noise generated by wind turbines is significantly impacted by its propagation in the atmosphere. Hence, for annoyance issues, an accurate prediction of sound propagation is critical to determine noise levels around wind turbines. This study presents a method to predict wind turbine sound propagation based on linearized Euler equations. We compare this approach to the parabolic equation method, which is widely used since it captures the influence of atmospheric refraction, ground reflection, and sound scattering at a low computational cost. Using the linearized Euler equations is more computationally demanding but can reproduce more physical effects as fewer assumptions are made. An additional benefit of the linearized Euler equations is that they provide a time-domain solution. To compare both approaches, we simulate sound propagation in two distinct scenarios. In the first scenario, a wind turbine is situated on flat terrain; in the second, a turbine is situated on a hilltop. The results show that both methods provide similar noise predictions in the two scenarios. We find that while some differences in the propagation results are observed in the second case, the final predictions for a broadband extended source are similar between the two methods. (10.1121/10.0020834)
  DOI : 10.1121/10.0020834
• Numerical Investigations of a Two-Way Coupled Fluid–Structure Interaction Approach for Fast Transients in Fluid-Filled Flexible Piping Systems
  
  • Daude Frédéric
  • Galon Pascal
  • Shams Afaque
  Arabian Journal for Science and Engineering, King Fahd University of Petroleum and Minerals - Springer, 2023, 285, pp.107083. (10.1007/s13369-023-08045-8)
  DOI : 10.1007/s13369-023-08045-8
• MEALOR II Damage Mechanics and Local Approach to Fracture
  
  • Besson Jacques
  • Bleyer Jérémy
  • Feld-Payet Sylvia
  • Gourgues-Lorenzon Anne-Françoise
  • Hannard Florent
  • Helfer Thomas
  • Hure Jeremy
  • Kondo Djimedo
  • Lazarus Veronique
  • Le Bourlot Christophe
  • Maitournam Habibou
  • Maurini Corrado
  • Moes Nicolas
  • Morgeneyer Thilo
  • Morin Léo
  • Petit Tom
  • Simar Aude
  , 2023, pp.441 p.. The MEALOR II summer school, held in Banyuls, France from August 21st to September 1st, 2023, sought to offer participants a comprehensive understanding of the physics and mechanics of brittle and ductile fracture under monotonic loading. Covering theoretical, numerical, and experimental foundations, as well as the latest applications and research developments of the local approach to fracture, the book compiles lecture materials delivered during the summer school, with a significant focus on fundamental fracture mechanisms. (10.5281/zenodo.10125170)
  DOI : 10.5281/zenodo.10125170
• An acoustic-transport splitting method for the barotropic Baer-Nunziato two-phase flow model
  
  • Ait-Ameur Katia
  • Kokh Samuel
  • Massot Marc
  • Pelanti Marica
  • Pichard Teddy
  ESAIM: Proceedings and Surveys, EDP Sciences, 2023, 72, pp.93-116. This work focuses on the numerical approximation of the barotropic Baer-Nunziato twophase flow model. The scheme relies on an operator splitting method corresponding to a separate treatment of fast propagation phenomena due to the acoustic waves on the one hand and slow propagation phenomena due to the fluid motion on the other. We propose to extend the implicit-explicit schemes developed in [7]. These methods enable the use of time steps that are no longer constrained by the sound velocity thanks to an implicit treatment of the acoustic waves, and maintain accuracy in the subsonic regime thanks to an explicit treatment of the material waves. In the present setting, a particular attention will be also given to the discretization of the non conservative terms in the Baer-Nunziato model. We prove that the proposed numerical strategy preserve positive values of the volume fractions and densities and we illustrate its behaviour with several relevant test cases. (10.1051/proc/202372093)
  DOI : 10.1051/proc/202372093
• Stability and Bifurcation in non linear mechanics
  
  • Stolz Claude
  , 2023. Analysis of stability and bifurcation is studied in non linear mechanics with mechanisms of dissipation : plasticity, damage, fracture. With introduction of a set of internal variables, this framework allows a systematic description of the material behaviour via two potentials : the free energy and the potential of dissipation. For standard generalized materials internal state evolution is governed by a variational inequality depending on the mechanism of dissipation. This inequality is obtained through energetic considerations in an unified description based upon energy and driving forces associated to internal variable evolution. This formulation provides criterion for existence and uniqueness of the system evolution. Examples are presented for plasticity, fracture and for damaged materials
• In-situ characterization of Soil Structure Interaction through measurement of Impedance Functions
  
  • Clement Julien
  • Lancieri Maria
  • Bouhjiti David
  • Semblat J F
  • Richard Benjamin
  , 2024, 2647 (25), pp.252011. In situ characterization of structural behaviour under seismic hazard provides an opportunity to acquire experimental data that improve our understanding of soil-structure interaction (SSI). Experimental programs such as Lotung and Hualien in Taiwan, EuroProteas in Greece and NUPEC in Japan, are amongst the most known. Such investigations aim at studying a structure with a rigid shallow raft and measuring the seismic impedance functions at soil-foundation interface. Indeed, impedance functions are by far the most widely used tools to study SSI. In this paper, considering feedbacks from these in situ tests, we aim at assessing the feasibility to acquire measurements of the seismic impedance functions for any structure with a rigid shallow foundation. To test the proposed methodology, we carry out a laboratory test with a small-scale device: the soil is represented by a model material (silicon rubber block) and the foundation by a cylindrical shaker inducing monitored harmonic vertical forces on the silicon rubber block. Experimental tests are paired with numerical simulations to identify, by inverse analysis, unknown parameters and to compute the order of magnitude of displacements and forces within the system. This paper presents the laboratory test setup, the experimental design, and the results of the associated simulations. (10.1088/1742-6596/2647/25/252011)
  DOI : 10.1088/1742-6596/2647/25/252011
• A 1-D/3-D coupling approach for compressible non-equilibrium two-phase flows using the Baer-Nunziato model based on the Finite-Volume framework
  
  • Daude Frédéric
  Computer Physics Communications, Elsevier, 2023, 288, pp.108724. (10.1016/j.cpc.2023.108724)
  DOI : 10.1016/j.cpc.2023.108724
• Scalable block preconditioners for saturated thermo-hydro-mechanics problems
  
  • Ordonez Ana C.
  • Tardieu Nicolas
  • Kruse Carola
  • Ruiz Daniel
  • Granet Sylvie
  Advanced Modeling and Simulation in Engineering Sciences, Springer, 2023, 10 (1), pp.1-31. We are interested in the modelling of saturated thermo-hydro-mechanical (THM) problems that describe the behaviour of a soil in which a weakly compressible fluid evolves. It is used for the evaluation of the THM impact of high-level activity radioactive waste exothermicity within a deep geological disposal facility. We shall present the definition of a block preconditioner with nested Krylov solvers for the fully coupled THM equations. Numerical results reflect the good performance of the proposed preconditioners that show to be weakly scalable until more than 2000 cores and more than 1 billion degrees of freedom. Thanks to their performance and robustness, a real waste storage problem on a scale, to our knowledge, unprecedented in the field, can be addressed. (10.1186/s40323-023-00245-z)
  DOI : 10.1186/s40323-023-00245-z