Publications

2018

• Constraint regularization of a non-smooth damage model.
  
  • Valoroso Nunziante
  • Stolz Claude
  , 2018.
• Analysis of stability and bifurcation in non-linear mechanics with dissipation
  
  • Stolz Claude
  , 2018.
• Improvements in the accuracy of the theta-method for the computation of the stress intensity factor in 3d.
  
  • Le Cren Mathieu
  • Martin Alexandre
  • Stolz Claude
  • Moes Nicolas
  • Massin Patrick
  , 2018.
• Wiedemann-Steiner syndrome as a major cause of syndromic intellectual disability: A study of 33 French cases
  
  • Baer S.
  • Afenjar A.
  • Smol T.
  • Piton A.
  • Gérard B.
  • Alembik Y.
  • Bienvenu T.
  • Boursier G.
  • Boute O.
  • Colson Cindy
  • Cordier M.-P.
  • Cormier-Daire V.
  • Delobel B.
  • Doco-Fenzy M.
  • Duban-Bedu B.
  • Fradin M.
  • Geneviève D.
  • Goldenberg A.
  • Grelet M.
  • Haye D.
  • Heron D.
  • Isidor B.
  • Keren B.
  • Lacombe D.
  • Lèbre A.-S.
  • Lesca G.
  • Masurel A.
  • Mathieu-Dramard M.
  • Nava C.
  • Pasquier L.
  • Petit A.
  • Philip N.
  • Piard J.
  • Rondeau S.
  • Saugier-Veber P.
  • Sukno S.
  • Thevenon J.
  • Van-Gils J.
  • Vincent-Delorme C.
  • Willems M.
  • Schaefer E.
  • Morin G.
  Clinical Genetics, Wiley, 2018, 94 (1), pp.141-152. Wiedemann-Steiner syndrome (WSS) is a rare syndromic condition in which intellectual disability (ID) is associated with hypertrichosis cubiti, short stature, and characteristic facies. Following the identification of the causative gene (KMT2A) in 2012, only 31 cases of WSS have been described precisely in the literature. We report on 33 French individuals with a KMT2A mutation confirmed by targeted gene sequencing, high-throughput sequencing or exome sequencing. Patients' molecular and clinical features were recorded and compared with the literature data. On the molecular level, we found 29 novel mutations. We observed autosomal dominant transmission of WSS in 3 families and mosaicism in one family. Clinically, we observed a broad phenotypic spectrum with regard to ID (mild to severe), the facies (typical or not of WSS) and associated malformations (bone, cerebral, renal, cardiac and ophthalmological anomalies). Hypertrichosis cubiti that was supposed to be pathognomonic in the literature was found only in 61% of our cases. This is the largest series of WSS cases yet described to date. A majority of patients exhibited suggestive features, but others were less characteristic, only identified by molecular diagnosis. The prevalence of WSS was higher than expected in patients with ID, suggesting than KMT2A is a major gene in ID. (10.1111/cge.13254)
  DOI : 10.1111/cge.13254
• Low cycle fatigue of shape memory alloys
  
  • Zhang Yahui
  , 2018. The thesis proposes a multi-scale comprehensive analysis of low cycle fatigue of shape memory alloys (SMAs). First, low cycle fatigue of SMAs is experimentally investigated; comprehensive tensile-tensile fatigue tests under both stress and strain controlled loadings at different frequencies are carried out and results are discussed. Second, a new strain energy-based fatigue criterion is developed; it is shown that the use of total strain energy is a relevant parameter to predict fatigue lifetime of SMAs for different thermomechanical conditions and under different types (strain-control or stress-control) loadings. A physical interpretation of the mechanism related to the low-cycle fatigue of SMAs is then provided based on the conversion of hysteresis work into dissipation and stored energy. Third, fatigue crack initiation during cyclic stress-induced phase transformation is modeled based on transformation induced plasticity (TRIP); it is shown that the maximum temperature during the cyclic loading is a relevant indicator of the fatigue of SMA. Furthermore, the effect of the macroscopic mechanical load on the the fatigue lifetime is addressed as well as the spatial location of crack initiation. Finally, a mechanical training process that allows enhancing resistance to low cycle fatigue of SMAs is proposed. (10.70675/56af35ffzed6bz4431za408z798a351ee69a)
  DOI : 10.70675/56af35ffzed6bz4431za408z798a351ee69a
• Optimized non-parametric fragility curve estimation based on intensity measure data clustering and parametric model averaging
  
  • Trevlopoulos K.
  • Feau C.
  • Zentner I.
  , 2018. In the context of seismic risk analysis, the mean annual rate of failure of a structure is computed by integrating the seismic fragility curve with respect to the seismic hazard curve. Seismic fragility curves are used to describe the seismic vulnerability of structures and give the failure probability conditioned on ground motion intensity. Lognormal fragility curves are commonly used, while differences between lognormal and non-parametric fragility curves have been observed. Usually, the number of available real records is insufficient for estimating fragility curves with small uncertainty and synthetic ground motions are used. Here, a database of real ground motions is enriched with spectrally equivalent synthetic ground motions. Time-history analyses of a single degree of freedom structure are used to compute engineering demand parameter observations as a function of the ground motion intensity measure. Clustering of the intensity measure observations based on the combined real and synthetic ground motion database is used and an empirical distribution of the engineering demand parameter observations is estimated for every cluster and used to compute the probability of exceeding the damage state threshold. Thus, fragility curves are represented non-parametrically as failure probabilities conditioned on the intensity measure cluster centroids. It is shown that an optimization based on parametric model averaging of the models constituting the aggregate fragility curve may lead to a non-parametric fragility curve which is more precise than the un-optimized curve based on the same number of seismic response analyses.
• On bounding global behaviour for composite with imperfect interface between phases
  
  • Stolz Claude
  , 2018.
• Reduced-order modeling of the fluidic pinball
  
  • Deng Nan
  • Marek Morzyński
  • Pastur Luc
  , 2018, pp.205-214. The fluidic pinball is a geometrically simple flow configuration with three rotating cylinders on the vertex of an equilateral triangle. Yet, it remains physically rich enough to host a range of interacting frequencies and to allow testing of control laws within minutes on a laptop. The system has multiple inputs (the three cylinders can independently rotate around their axis) and multiple outputs (downstream velocity sensors). Investigating the natural flow dynamics, we found that the first unsteady transition undergone by the wake flow, when increasing the Reynolds number, is a Hopf bifurcation leading to the usual time-periodic vortex shedding phenomenon, typical of cylinder wake flows, in which the mean flow field preserves axial symmetry. We extract dynamically consistent modes from the flow data in order to built a reduced-order model (ROM) of this flow regime. We show that the main dynamical features of the primary Hopf bifurcation can be described by a non-trivial lowest-order model made of three degrees of freedom.
• Microstructure and properties of bulk Al 0.5 CoCrFeNi high-entropy alloy by cold rolling and subsequent annealing
  
  • Guo Tong
  • Li Jinshan
  • Wang Jun
  • Wang William Yi
  • Li Yi
  • Luo Ximing
  • Kou Hongchao
  • Beaugnon Eric
  Materials Science and Engineering: A, Elsevier, 2018, 729, pp.141-148. (10.1016/j.msea.2018.05.054)
  DOI : 10.1016/j.msea.2018.05.054
• A Finite-Volume approach for compressible single- and two-phase flows in flexible pipelines with fluid-structure interaction
  
  • Daude Frédéric
  • Galon Pascal
  Journal of Computational Physics, Elsevier, 2018. A Finite-Volume scheme for the numerical computations of compressible single- and two-phase flows in flexible pipelines is proposed based on an approximate Godunov-type approach. The spatial discretization is here obtained using the HLLC scheme. In addition, the numerical treatment of abrupt changes in area and network including several pipelines connected at junctions is also considered. The proposed approach is based on the integral form of the governing equations making it possible to tackle general equations of state. A coupled approach for the resolution of fluid-structure interaction of compressible fluid flowing in flexible pipes is considered. The structural problem is solved using Euler–Bernoulli beam finite elements. The present Finite-Volume method is applied to ideal gas and two-phase steam-water based on the Homogeneous Equilibrium Model (HEM) in conjunction with a tabulated equation of state in order to demonstrate its ability to tackle general equations of state. The extensive application of the scheme for both shock tube and other transient flow problems demonstrates its capability to resolve such problems accurately and robustly. Finally, the proposed 1-D fluid-structure interaction model appears to be computationally efficient. (10.1016/j.jcp.2018.01.055)
  DOI : 10.1016/j.jcp.2018.01.055
• Nonsmooth contact dynamics for the numerical simulation of collisions in musical string instruments
  
  • Issanchou Clara
  • Acary Vincent
  • Pérignon Franck
  • Touzé Cyril
  • Le Carrou Jean-Loic
  Journal of the Acoustical Society of America, Acoustical Society of America, 2018, 143 (5), pp.1-13. Collisions in musical string instruments play a fundamental role in explaining the sound production in various instruments such as sitars, tanpuras and electric basses. Contacts occuring during the vibration provide a nonlinear effect which shapes a specific tone due to energy transfers and enriches the hearing experience. As such, they must be carefully simulated for the purpose of physically-based sound synthesis. Most of the numerical methods presented in the literature rely on a compliant modeling of the contact force between the string and the obstacle. In this contribution, numerical methods from nonsmooth contact dynamics are used to integrate the problem in time. A Moreau-Jean time-stepping scheme is combined with an exact scheme for phases with no contact, thus controlling the numerical dispersion. Results for a two-point bridge mimicking a tanpura and an electric bass are presented, showing the ability of the method to deal efficiently with such problems while invoking, as compared to a compliant approach, less modelling parameters and a reduced computational burden. (10.1121/1.5039740)
  DOI : 10.1121/1.5039740
• Modelling and numerical simulation of metastable two-phase flows
  
  • de Lorenzo Marco
  , 2018. This Ph.D. thesis deals with the metastable two-phase flows typical of accidental transients that could occur in nuclear power plants. Those phenomena are of difficult treatment due to the topological difficulty of the flow, the interphase transfers and the strong coupling between thermodynamic features and mathematical aspects.The methods today in use in industry do not fully describe the complexity of these flows because based on too simple models. In fact, they do not take into account the thermo-chemical disequilibrium between liquid and vapor water. On the other hand, the hyperbolic methods recently proposed in the literature for the simulation of metastable flows can not be used in the industry because based on simple equations of state that are not adequate for industrial calculations.The purpose of this Ph.D. thesis is to develop a new approach that couples the modern hyperbolic methods to accurate equations of state. The final product of this work is a new model for the industrial analysis of metastable two-phase flows that incorporates novel techniques for the calculation of interfacial transfers and of steam-water properties. Moreover, it is computationally affordable for its use in industrial configurations.The methods developed in this thesis have been sistematically verified against exact solutions and validated using experimental data of the literature. (10.70675/42d9fdcfz3725z41cfzba0azc8232843b751)
  DOI : 10.70675/42d9fdcfz3725z41cfzba0azc8232843b751
• Pwr effect on crack initiation under equi-biaxial loading
  
  • Gourdin C.
  • Dhahri H.
  • Perez G.
  • Courtin S.
  • Le Roux Jc.
  • Maitournam H.
  , 2018. The lifetime extension of the nuclear power stations is considered as an energy challenge worldwide. That is why, the risk analysis and the study of various effects of different factors that could potentially represent a hazard to a safe long term operation are necessary. These structures, often of great dimensions, are subjected during their life to complex loading combining varying mechanical loads, multiaxial, with non-zero mean values associated with temperature fluctuations and also PWR environment. Historically, the methodology for fatigue design of the Pressurized Water Reactor components (PWR) (ASME BPV III, RCC-M, JSME, EN-13445-3, Chopra O.K. and Shack W.J. (2007)) is based on the use of design curves established from tests carried out in air at 20°C on smooth specimens by integrating safety coefficients that cover, among other parameters, the dispersion of tests associated with the effects of structures. Based on more recent fatigue data (including tests at 300°C in air and PWR environment, etc…), some international codes (RCC-M, ASME and others) have introduced a modification of the austenitic stainless steels fatigue curve combined with a calculation of an environmental penalty factor, namely Fen, which has to be multiplied by the usual fatigue usage factor. The 304L and the 316L stainless steel are used for the manufacturing of the pressurized water reactors (PWR). Many components of this type of reactors are subjected to a multiaxial thermo-mechanical cycling. Therefore, the multiaxial fatigue assisted by environment may be considered as one of the main possible degradation mechanisms affecting the life of the PWR components. Unfortunately, experimental data on this issue are rare. In order to obtain fatigue strength data under structural loading, biaxial test means with and without PWR environment were developed at LISN in collaboration with EDF and AREVA. Two kinds of fatigue device have been developed. Within the same specimen geometry, structural loads can be applied in varying only the PWR environment. The first device (FABIME2) is devoted to study the effect of biaxiality and mean strain/stress on the fatigue life. A second and new device based on FABIME2 is for the study of the impact of the environmental effect. With these new experimental results, the possible PWR environment effect on the fatigue life of stainless austenitic steels will be discussed. These tests allow quantifying accurately the effect of PWR environment on semi-structure specimen. This device combines the structural effect like equi-biaxiality and mean strain and the environmental penalty effect with the use of PWR environment during the fatigue tests.
• Modélisation numérique tridimensionnelle de l'interaction sol-structure avec prise en compte des effets de site
  
  • Adnani Zouhair
  , 2018. L'un des enjeux de l'analyse du risque sismique est de déterminer les marges de sûreté des structures. Dans cette optique, la modélisation numérique des effets de site est importante. En effet, la géométrie du site et ses propriétés lithologiques peuvent induire des amplifications ou atténuations du mouvement sismique. Les effets de site étant souvent découplés des calcul d'interaction sol-structure, à cause de la taille des domaines à considérer et de la complexité des modèles, l'objectif de cette thèse est de développer une stratégie de calcul numérique d'interaction sol-structure permettant de prendre en compte les effets de site dans un contexte industriel. Pour ce faire, un couplage entre la méthode des éléments finis (FEM) et la méthode des éléments de frontière accélérée par la méthode multipôle rapide (FM-BEM) est développé dans ce travail. La BEM permet de modéliser des problèmes dans des domaines de très grande taille ou infinis mais est gourmande en temps de calculs. Avec la méthode accélérée, il est possible de considérer des géologies plus complexes et d'accéder à des gammes de fréquences plus élevées par rapport à des approches classiques (purement FEM ou couplage BEM-FEM), grâce à l'accélération du produit matrice-vecteur dans la résolution par un solveur itératif. La mise en place de cette approche s'appuie sur le code FEM industriel Code_Aster (EDF R&D) et le code FM-BEM Coffee (CNRS) développé par S. Chaillat.La FM-BEM est d'abord utilisée pour la modélisation de cas de sols réalistes afin de valider ses paramètres pour une utilisation dans un cadre industriel. Une stratégie de couplage FM-BEM/FEM est ensuite développée à l'aide d'une technique de sous-structuration dynamique où la structure (et éventuellement le sol proche) est modélisée par la FEM, alors que le sol infini est représenté par un opérateur d'impédance et des forces sismiques, construits avec la méthode FM-BEM. L'opérateur d'impédance et les forces sismiques, qui sont calculés sur une base réduite afin d'en réduire le coût de calcul, sont validés sur des cas canoniques (demi-espace homogène, bassin à géométrie variable...). L'influence sur la réponse de la structure de la forme du bassin, de l'angle d'incidence des ondes ainsi que du rapport de célérité des ondes entre les couches est alors étudiée et la réponse de la structure comparée aux cas où les effets de site seraient absents. Enfin, la méthodologie de couplage mise en place est utilisée pour effectuer des calculs d'interaction sol-structure sur des structures dans le bassin de Grenoble. (10.70675/ef9897f3z9a02z4bbdzb7a0z0b6dc93253fb)
  DOI : 10.70675/ef9897f3z9a02z4bbdzb7a0z0b6dc93253fb
• A parallel non-invasive multiscale strategy for a mixed domain decomposition method with frictional contact
  
  • Oumaziz Paul
  • Gosselet Pierre
  • Boucard Pierre-Alain
  • Abbas Mickaël
  International Journal for Numerical Methods in Engineering, Wiley, 2018, 115 (8), pp.893-912. A parallel multiscale strategy for a non-invasive mixed domain decomposition method is presented. After briefly exposing our non-invasive implementation of the Latin method, we present how the scalability of the algorithm is obtained by the addition of a global verification of the constitutive law of the interfaces. We propose a new interpretation of the classical macro strategy that impose a global equilibrium of interface's forces. We also propose a new study of a macro strategy that permits to enforce a global continuity of displacement at the interface. (10.1002/nme.5830)
  DOI : 10.1002/nme.5830
• Caractérisation de la fatigue des assemblages soudés soumis à des chargements à amplitude variable
  
  • Pierron Quentin
  , 2018. Dans le monde de l'automobile, les ingénieurs conçoivent des pièces de plus en plus légères pour répondre aux nouvelles normes de dépollution. En particulier, les pièces soudées à l’arc de la Liaison Au Sol (LAS) qui soutiennent une part du poids des véhicules doivent tenir à la fatigue malgré des épaisseurs de tôle relativement fines. Pour dimensionner les assemblages soudés, des chargements à amplitude constante sont utilisés : à la fois pour la caractérisation à la fatigue des matériaux et des assemblages mais aussi dans les calculs de champs mécaniques. Toutefois, les chargements réels vus par les pièces en service leurs sont différents. Les cahots sur la route, les virages et les freinages induisent des efforts dont l’évolution temporelle est complexe. Plusieurs modèles prédisent la durée de vie sous un chargement complexe à partir de chargement à amplitude constante. Parmi ces modèles, le modèle de cumul linéaire considère que l’endommagement créé par un cycle de chargement est indépendant du chargement qui le précède. Les résultats de la littérature contredisent cette hypothèse. Cette dernière peut induire des erreurs de dimensionnement importantes. Des modèles de cumul d’endommagement alternatifs de la littérature sont alors évalués. De plus, des essais sur structures soudées minces sont mis en œuvre pour compléter les résultats expérimentaux disponibles et ainsi contribuer à la compréhension du cumul d’endommagement sous chargements à amplitude variable. Un soin particulier a été pris pour concevoir, instrumenter, modéliser et comprendre ces essais. Les effets de déformée due au soudage et de maintien des éprouvettes sont analysés et pris en compte. Des mesures de champ de température sont utilisées pour identifier la dissipation qui permet un suivi indirect de l’endommagement. C’est une extension de la méthode de caractérisation de la limite d’endurance par auto-échauffement à l’endurance limitée des structures soudées sous chargement à amplitude variable. Les essais révèlent deux phénomènes de cumul d’endommagement non linéaire à effets contraires. D’une part, les surcharges créent des contraintes résiduelles de compression qui augmentent la durée de vie des assemblages soudés. D’autre part, la répétition des surcharges empêche l’adaptation locale. À la lumière de ces essais, des préconisations sont finalement données pour les chargements de fatigue et les modèles de cumul d’endommagement adaptés aux structures soudées. (10.70675/f193f3bbz330ez431bz9084zcc88892ea9e0)
  DOI : 10.70675/f193f3bbz330ez431bz9084zcc88892ea9e0
• A Mach-Sensitive Splitting Approach for Euler-like Systems
  
  • Iampietro David
  • Daude Frédéric
  • Galon Pascal
  • Hérard Jean-Marc
  ESAIM: Mathematical Modelling and Numerical Analysis, Société de Mathématiques Appliquées et Industrielles (SMAI) / EDP, 2018, 52 (1), pp.207-253. Herein, a Mach-sensitive fractional step approach is proposed for Euler-like systems. The key idea is to introduce a time-dependent splitting which dynamically decouples convection from acoustic phenomenon following the fluctuations of the flow Mach number. By doing so, one seeks to maintain the accuracy of the computed solution for all Mach number regimes. Indeed, when the Mach number takes high values, a time-explicit resolution of the overall Euler-like system is entirely performed in one of the present splitting step. On the contrary, in the low-Mach number case, convection is totally separated from the acoustic waves production. Then, by performing an appropriate low-Mach correction on the acoustic step of the splitting, the numerical diffusion can be significantly reduced. A study made on both convective and acoustic subsystems of the present approach has revealed some key properties as hyperbolicity and positivity of the density and internal energy in the case of an ideal gas thermodynamics. The one-dimensional results made on a wide range of Mach numbers using an ideal and a stiffened gas thermodynamics show that the present approach is as accurate and CPU-consuming as a state of the art Lagrange-Projection-type method. (10.1051/m2an/2017063)
  DOI : 10.1051/m2an/2017063
• Analysis of the failure at notches and cavities in quasi-brittle media using the Thick Level Set damage model and comparison with the coupled criterion
  
  • Zghal Jihed
  • Moreau Kevin
  • Moës Nicolas
  • Leguillon Dominique
  • Stolz Claude
  International Journal of Fracture, Springer Verlag, 2018, 211 (1-2), pp.253-280. The failure of quasi-brittle specimen weakened by sharp or blunted notches and cavities is analyzed under quasi-static loading. The load at failure is obtained with the Thick Level Set (TLS) damage modeling. In this model, the damage gradient is bounded implying that the minimal distance between a point where damage 0 (sound material) to 1 (fully damaged) is an imposed characteristic length in the model. This length plays an important role on the damage evolution and on the failure load. The paper shows that the TLS predictions are relevant. A comparison with the coupled criterion (CC) of Leguillon (2002) is given. A good agreement is obtained for cavities and V-notches provided that the characteristic length of Irwin is small compared to the notch depth (condition for the applicability of the CC criterion). A comparison with failure loads obtained experimentally is also given. In the numerical simulations, uniform stresses are imposed at infinity using a new finite element mapping technique (Cloirec 2005). (10.1007/s10704-018-0287-6)
  DOI : 10.1007/s10704-018-0287-6
• Optimal control approach to simulating wear under cyclic loading
  
  • Stolz Claude
  , 2018.
• Effect of Solidification on Microstructure and Properties of FeCoNi(AlSi)0.2 High-Entropy Alloy Under Strong Static Magnetic Field
  
  • Wang Jiaxiang
  • Li Jinshan
  • Wang Jun
  • Bu Fan
  • Kou Hongchao
  • Li Chao
  • Zhang Pingxiang
  • Beaugnon Eric
  Entropy, MDPI, 2018, 20 (4), pp.275. (10.3390/e20040275)
  DOI : 10.3390/e20040275
• Modeling the impacts of atmospheric deposition of nitrogen and desert dust-derived phosphorus on nutrients and biological budgets of the Mediterranean Sea
  
  • Richon Camille
  • Dutay Jean-Claude
  • Dulac François
  • Wang Rong
  • Balkanski Yves
  • Nabat Pierre
  • Aumont Olivier
  • Desboeufs Karine
  • Laurent Benoît
  • Guieu Cécile
  • Raimbault Patrick
  • Beuvier Jonathan
  Progress in Oceanography, Elsevier, 2018, 163, pp.21 - 39. Atmospheric deposition represents a significant source of nutrients at the Mediterranean basin scale. We apply aerosol deposition fields simulated from atmospheric models into the high resolution oceanic biogeochemical model NEMOMED12/PISCES with nutrient ratios used for plankton growth set to Redfield ratio. We perform 3 simulations to determine the impact of nutrients on productivity over the period 1997–2012: (i) without atmospheric deposition, (ii) with nitrogen deposition from anthropogenic and natural sources, and (iii) with deposition of both nitrogen (from anthropogenic and natural sources) and phosphate from desert dust. Time series of modeled deposition fluxes are compared to available measurements. This comparison with measurements shows that both variability and intensity ranges are realistic enough for our main purpose of estimating the atmospheric deposition impact on Mediterranean biogeochemical tracers such as surface nutrient concentrations, chlorophyll a and plankton concentrations. Our results show that atmospheric deposition is one of the major sources of nitrogen and phosphorus for some regions of the oligotrophic Mediterranean Sea. More than 18 · 10⁹gN month⁻¹ are deposited to the whole Mediterranean Sea. This deposition is responsible for an average increase of 30–50% in primary production over vast regions. Natural dust-derived deposition of phosphorus is sparser in space and time (0.5 · 10⁹ g month⁻¹ on average over the entire basin). However, dust deposition events can significantly affect biological production. We calculate fertilizing effects of phosphate from dust to be low on average (6–10%) but up to 30% increase in primary productivity can be observed during the months when surface water stratification occurs. Finally, these fertilizing effects are shown to be transmitted along the biological chain (primary production, Chl a, phytoplankton, zooplankton, grazing). We also perform a preliminary study on the maximal biological response of the Mediterranean by simulating extreme deposition events throughout the basin over a full year period. We show that nitrogen deposition effects observed in our long-term simulations (1997–2012) are close to maximal effects (i.e. those produced by high intensity deposition events) whereas dust-derived phosphate effects are substantially weaker than the effect on productivity reached when an extreme deposition event occurs. (10.1016/j.pocean.2017.04.009)
  DOI : 10.1016/j.pocean.2017.04.009
• A transversely isotropic thermo-poroelastic model for claystone: parameter identification and application to a 3D underground structure
  
  • Giot Richard
  • Granet Sylvie
  • Faivre Maxime
  • Massoussi Nadia
  • Huang Julie
  Geomechanics and Geoengineering, Taylor & Francis: STM, Behavioural Science and Public Health Titles, 2018, 13 (4), pp.246-263. A transversely isotropic thermo-poroelastic constitutive law is developed and implemented in the finite element code Code_Aster (EDF, France). It is then validated using an analytic solution for an inclined borehole in a transversely isotropic medium. A strategy for identifying the parameters of the transversely isotropic thermo-poroelastic model based on an inverse method is proposed on the basis of different laboratory tests. To demonstrate the efficiency and applicability of the model, it is then applied in a three-dimensional numerical model of an underground structure in a parameter sensitivity study. The results of the modelling highlight the importance of accounting for anisotropic phenomena when determining the dimensions of underground facilities. The whole approach is presented in the paper, from model development to application to 3D numerical modelling to an engineering case study. (10.1080/17486025.2018.1445874)
  DOI : 10.1080/17486025.2018.1445874
• Cross flow induced vibration in a single tube of square array using LES
  
  • Shinde Vilas
  • Longatte Elisabeth
  • Baj Franck
  • Hoarau Yannick
  • Braza Marianna
  , 2018, 137, pp.479-489. Large eddy simulations (LES) of a single phase water flow through a square normal tube bundle at Reynolds numbers from 2000 to 6000 is performed to investigate the fluid-elastic instability. A single cylinder of the array is allowed to oscillate in one degree of freedom (1-DOF) in the flow normal direction, similar as in the corresponding experiments. The fluid-structure coupling is simulated using the Arbitrary Lagrangian-Eulerian (ALE) approach. The subgrid scale turbulence is modeled using the standard Smagorinsky’s eddy-viscosity model. The LES results show a good agreement with the experimental results, in terms of the response frequency and damping ratio of the cylinder vibration. The dynamic case simulations are compared with static cases over the range of Reynolds numbers by means of the pressure profiles on the cylinder surface and the probe velocity spectra (10.1007/978-3-319-70031-1_40)
  DOI : 10.1007/978-3-319-70031-1_40
• Modelling resonant arrays of the Helmholtz type in the time domain
  
  • Maurel Agnès
  • Marigo Jean-Jacques
  • Mercier Jean-François
  • Pham Kim
  Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Royal Society, 2018, 474 (2210), pp.20170894. We present a model based on a two-scale asymptotic analysis for resonant arrays of the Helmholtz type, with resonators open at a single extremity (standard resonators) or open at both extremities (double-sided resonators). The effective behaviour of such arrays is that of a homogeneous anisotropic slab replacing the cavity region, associated with transmission, or jump, conditions for the acoustic pressure and for the normal velocity across the region of the necks. The coefficients entering in the effective wave equation are simply related to the fraction of air in the periodic cell of the array. Those entering in the jump conditions are related to near field effects in the vicinity of the necks and they encapsulate the effects of their geometry. The effective problem, which accounts for the coupling of the resonators with the surrounding air, is written in the time domain which allows us to question the equation of energy conservation. This is of practical importance if the numerical implementations of the effective problem in the time domain is sought. (10.1098/rspa.2017.0894)
  DOI : 10.1098/rspa.2017.0894
• Hybrid High-Order methods for finite deformations of hyperelastic materials
  
  • Abbas Mickaël
  • Ern Alexandre
  • Pignet Nicolas
  Computational Mechanics, Springer Verlag, 2018, 62 (4), pp.909-928. We devise and evaluate numerically Hybrid High-Order (HHO) methods for hyperelastic materials undergoing finite deformations. The HHO methods use as discrete unknowns piece-wise polynomials of order k ≥ 1 on the mesh skeleton, together with cell-based polynomials that can be eliminated locally by static condensation. The discrete problem is written as the minimization of the broken nonlinear elastic energy where a local reconstruction of the displacement gradient is used. Two HHO methods are considered: a stabilized method where the gradient is reconstructed as a tensor-valued polynomial of order k and a stabilization is added to the discrete energy functional, and an unstabilized method which reconstructs a stable higher-order gradient and circumvents the need for stabilization. Both methods satisfy the principle of virtual work locally with equilibrated tractions. We present a numerical study of both HHO methods on test cases with known solution and on more challenging three-dimensional test cases including finite deformations with strong shear layers and cavitating voids. We assess the computational efficiency of both methods, and we compare our results to those obtained with an industrial software using conforming finite elements and to results from the literature. Both methods exhibit robust behavior in the quasi-incompressible regime. (10.1007/s00466-018-1538-0)
  DOI : 10.1007/s00466-018-1538-0