Publications

2018

• A discrete forcing method dedicated to moving bodies in two‐phase flow
  
  • Benguigui William
  • Doradoux Antoine
  • Laviéville Jérôme
  • Mimouni Stephane
  • Longatte Elisabeth
  International Journal for Numerical Methods in Fluids, Wiley, 2018, 88 (7), pp.315-333. The numerical simulation of interaction between structures and two‐phase flows is a major concern for many industrial applications. To address this challenge, the motion of structures has to be tracked accurately. In this work, a discrete forcing method based on a porous medium approach is proposed to follow a nondeformable rigid body with an imposed velocity by using a finite‐volume Navier‐Stokes solver code dedicated to multiphase flows and based on a two‐fluid approach. To deal with the action reaction principle at the solid wall interfaces in a conservative way, a porosity is introduced allowing to locate the solid and insuring no diffusion of the fluid‐structure interface. The volumetric fraction equilibrium is adapted to this novelty. Mass and momentum balance equations are formulated on a fixed Cartesian grid. Interface tracking is addressed in detail going from the definition of the porosity to the changes in the discretization of the momentum balance equation. This so‐called time‐ and space‐dependent porosity method is then validated by using analytical and elementary test cases. (10.1002/fld.4670)
  DOI : 10.1002/fld.4670
• A theoretical model of fluidelastic instability in tube arrays
  
  • Shinde Vilas
  • Longatte Elisabeth
  • Baj F.
  • Braza Marianna
  Nuclear Engineering and Design, Elsevier, 2018, 337, pp.406-418. A theoretical model of the fluidelastic instability in tube arrays is presented in this article. It is developed for a normal-square cylinder array and then extended to other types of array patterns. The model is based on transient interactions between a single cylinder and the adjacent flow streams of single phase fluid. The central cylinder is assumed to oscillate as a one-degree-of-freedom mass on a spring system in the lift direction only. A small displacement of cylinder is assumed to perturb the surrounding interstitial flow, while as for higher displacements the cylinder causes flow distortions in regular intervals. These disturbances are convected downstream along with the interstitial flow. The waveforms of these flow distortions are assumed to interact with the array pattern, thence modifying the fluid force acting on the cylinder. The critical flow velocity is obtained as a function of mass ratio and damping parameter. The proportionality constant of the mathematical model is derived in terms of the pitch ratio and Euler number. The mathematical development results in an implicit model for the critical flow velocity. The model predictions are in a good agreement with experimental results. (10.1016/j.nucengdes.2018.07.011)
  DOI : 10.1016/j.nucengdes.2018.07.011
• Coupling of an aeroacoustic model and a parabolic equation code for long range wind turbine noise propagation
  
  • Cotté Benjamin
  Journal of Sound and Vibration, Elsevier, 2018, 422, pp.343-357. This study proposes to couple a source model based on Amiet's theory and a parabolic equation code in order to model wind turbine noise emission and propagation in an inhomogeneous atmosphere. Two broadband noise generation mechanisms are considered, namely trailing edge noise and turbulent inflow noise. The effects of wind shear and atmospheric turbulence are taken into account using the Monin-Obukhov similarity theory. The coupling approach, based on the backpropagation method to preserve the directivity of the aeroa-coustic sources, is validated by comparison with an analytical solution for the propagation over a finite impedance ground in a homogeneous atmosphere. The influence of refraction effects is then analyzed for different directions of propagation. The spectrum modification related to the ground effect and the presence of a shadow zone for upwind receivers are emphasized. The validity of the point source approximation that is often used in wind turbine noise propagation models is finally assessed. This approximation exaggerates the interference dips in the spectra, and is not able to correctly predict the amplitude modulation. (10.1016/j.jsv.2018.02.026)
  DOI : 10.1016/j.jsv.2018.02.026
• Lagged effects of the Mistral wind on heavy precipitation through ocean-atmosphere coupling in the region of Valencia (Spain)
  
  • Berthou Ségolène
  • Mailler Sylvain
  • Drobinski Philippe
  • Arsouze Thomas
  • Bastin Sophie
  • Béranger Karine
  • Lebeaupin-Brossier Cindy
  Climate Dynamics, Springer Verlag, 2018, 51 (3), pp.969-983. The region of Valencia in Spain has historically been affected by heavy precipitation events (HPEs). These HPEs are known to be modulated by the sea surface temperature (SST) of the Balearic Sea. Using an atmosphere-ocean regional climate model, we show that more than 70 % of the HPEs in the region of Valencia present a SST cooling larger than the monthly trend in the Northwestern Mediterranean before the HPEs. This is linked to the breaking of a Rossby wave preceding the HPEs: a ridge-trough pattern at mid-levels centered over western France associated with a low-level depression in the Gulf of Genoa precedes the generation of a cut-off low over southern Spain with a surface depression over the Alboran Sea in the lee of the Atlas. This latter situation is favourable to the advection of warm and moist air towards the Mediterranean Spanish coast, possibly leading to HPEs. The depression in the Gulf of Genoa generates intense northerly (Mistral) to north-westerly (Tramontane/Cierzo) winds. In most cases, these intense winds trigger entrainment at the bottom of the oce-anic mixed layer which is a mechanism explaining part of the SST cooling in most cases. Our study suggests that the SST cooling due to this strong wind regime then persists until the HPEs and reduces the precipitation intensity. (10.1007/s00382-016-3153-0)
  DOI : 10.1007/s00382-016-3153-0
• Forcing symmetry exchanges and flow reversals in turbulent wakes
  
  • Barros Diogo
  • Borée Jacques
  • Cadot Olivier
  • Spohn Andreas
  • Noack Bernd R.
  Journal of Fluid Mechanics, Cambridge University Press (CUP), 2018, 829, pp.R1-10. Turbulent wakes past bluff bodies commonly present asymmetric flow states reminiscent of bifurcations in the laminar regime. Understanding the sensitivity of these states to flow forcing is crucial to the modelling and control of flow symmetry properties. In this study, the near wake of a rectangular bluff body in proximity to a wall is disturbed by the use of passive devices located between the model and the wall, upstream of the massive flow separation occurring at the blunt trailing edges. Due to the proximity to the boundary, the wake initially presents wall-normal asymmetry and a negative wall-normal pressure gradient along the base. The application of disturbances with variable size, however, sets flow symmetry along the wall-normal plane, leading to the intermittent spanwise wake reversals reported recently in the literature. A further increase in the size of perturbation suppresses wake switching, and wall-normal asymmetry is recovered, but with a positive wall-normal pressure gradient. The dynamical features of this bifurcation scenario can be retrieved using two coupled symmetry-breaking models for spanwise and wall-normal pressure gradients. This confirms the high sensitivity of the separated flow to external perturbations. More importantly, the results unify observations of the bluff-body wake topologies covered in previous investigations. (10.1017/jfm.2017.590)
  DOI : 10.1017/jfm.2017.590
• Numerical Study of Callovo-Oxfordian Argillite Expansion due to Gas Injection
  
  • Mahjoub Mohamed
  • Rouabhi Ahmed
  • Tijani Michel
  • Granet Sylvie
  • M’jahad Sofia
  • Talandier Jean
  International Journal of Geomechanics, American Society of Civil Engineers, 2018, 18 (1). (10.1061/(ASCE)GM.1943-5622.0001050)
  DOI : 10.1061/(ASCE)GM.1943-5622.0001050
• Equilibrated stress tensor reconstruction and a posteriori error estimation for nonlinear elasticity
  
  • Botti Michele
  • Riedlbeck Rita
  Computational Methods in Applied Mathematics, De Gruyter, 2018. We consider hyperelastic problems and their numerical solution using a conforming nite element discretization and iterative linearization algorithms. For these problems, we present equilibrated, weakly symmetric, Hpdivq-conforming stress tensor reconstructions, obtained from local problems on patches around vertices using the ArnoldFalkWinther nite element spaces. We distinguish two stress reconstructions, one for the discrete stress and one representing the linearization error. The reconstructions are independent of the mechanical behavior law. Based on these stress tensor reconstructions, we derive an a posteriori error estimate distinguishing the discretization, linearization, and quadrature error estimates, and propose an adaptive algorithm balancing these dierent error sources. We prove the eciency of the estimate, and conrm it on a numerical test with analytical solution for the linear elasticity problem. We then apply the adaptive algorithm to a more application-oriented test, considering the HenckyMises and an isotropic damage models. (10.1515/cmam-2018-0012)
  DOI : 10.1515/cmam-2018-0012
• Liquefaction analysis and damage evaluation of embankment-type structures
  
  • Rapti Ioanna
  • Lopez-Caballero Fernando
  • Modaressi-Farahmand Razavi Arézou
  • Foucault Alexandre
  • Voldoire François
  Acta Geotechnica, Springer Verlag, 2018, 13 (5), pp.1041-1059. The increasing importance of performance-based earthquake engineering analysis points out the necessity to assess quantitatively the risk of liquefaction of embankment-type structures. In this extreme scenario of soil liquefaction, devastating consequences are observed, e.g., excessive settlements, lateral spreading and slope instability. The present work discusses the global dynamic response and interaction of an earth structure-foundation system, so as to determine quantitatively the collapse mechanism due to foundation’s soil liquefaction. A levee-foundation system is simulated, and the influence of characteristics of input ground motion, as well as of the position of liquefied layer on the liquefaction-induced failure, is evaluated. For the current levee model, its induced damage level (i.e., induced crest settlements) is strongly related to both liquefaction apparition and dissipation of excess pore water pressure on the foundation. The respective role of input ground motion characteristics is a key component for soil liquefaction apparition, as long duration of mainshock can lead to important nonlinearity and extended soil liquefaction. A circular collapse surface is generated inside the liquefied region and extends toward the crest in both sides of the levee. Even so, when the liquefied layer is situated in depth, no significant effect on the levee response is found. This research work provides a reference case study for seismic assessment of embankment-type structures subjected to earthquake and proposes a high-performance computational framework accessible to engineers. (10.1007/s11440-018-0631-z)
  DOI : 10.1007/s11440-018-0631-z
• Toward a model for wall-slab junctions in nuclear reinforced concrete structures: first steps
  
  • Hervé-Secourgeon Estelle
  • Gatuingt Fabrice
  • Guilloux Adrien
  • Oliver-Leblond Cécile Oliver
  • Voldoire François
  , 2018. As part of the periodic reassessments of the safety of existing nuclear structures and the design of new ones, the contribution of wall-slab junctions to both behaviour and resistance of nuclear buildings subjected to seismic loadings is investigated. An experimental program has been defined jointly with the CEA [REF], in order to improve our knowledge of the junctions' behaviour. In parallel, work is underway in order to propose a model of the junctions, starting first from literature experimental observations and numerical detailed 3D computations results. Unlike previous global models for RC junctions in the literature, whose validity domain is generally limited either to out-of-plane or to in-plane stresses, our aim is to define a model fit to be integrated in a structural FE plate or shell model of a nuclear building. The purpose of this model is to represent the contribution of the junction to both stiffness and resistance when the building is subjected to seismic loads, that can include both in-plane and out-of-plane components. The purpose of this paper is to present the first steps achieved in the definition of this model, starting from the representation of the junctions in their elastic behaviour domain. Starting from the 3D kinematics in the joint area, a model of behaviour able to represent accurately the deformation modes of the elastic joint subjected to diverse loads has been selected. It is connected to plates elements which represent the behaviour of thin structural elements (walls, floors) in order to transmit the displacements and rotations at its interfaces. The boundary between the junction element and the plate elements representing walls and floors is set at the limit of the respective structural elements, thus increasing the representativeness of these FE models. The capacity of this model to effectively represent the joint stiffness is assessed in the elastic range, first considering a homogeneous material and then taking into account the presence of both concrete and reinforcement in the structure. A parametric study is carried out, in order to validate the model within the variation range of thicknesses, reinforcement ratio, etc. representative of nuclear buildings. The results are presented herein. In a second time, the framework of the non-linear model proposed to describe the junctions' behaviour beyond their elastic range is exposed.
• Highly porous layers of silica nanospheres sintered by drying: scaling up of the elastic properties of the beads to the macroscopic mechanical properties
  
  • Lesaine Arnaud
  • Bonamy Daniel
  • Gauthier Georges
  • Rountree Cindy Lynn
  • Lazarus Veronique
  Soft Matter, Royal Society of Chemistry, 2018, 14 (19), pp.3987-3997. Layers obtained by drying a colloidal dispersion of silica spheres are found to be a good benchmark to test the elastic behaviour of porous media, in the challenging case of high porosities and nanosized microstructures. Classically used for these systems, Kendall’s approach explicitely considers the effect of surface adhesive forces onto the contact area between the particles. This approach provides the Young’s modulus using a single adjustable parameter (the adhesion energy) but provides no further information on the tensorial nature and possible anisotropy of elasticity. On the other hand, homogenization approaches (e.g. rule of mixtures, Eshelby, Mori-Tanaka and self-consistent schemes), based on continuum mechanics and asymptotic analysis, provide the stiffness tensor from the knowledge of the porosity and the elastic constants of the beads. Herein, the self-consistent scheme accurately predicts both bulk and shear moduli, with no adjustable parameter, provided the porosity is less than 35%, for layers composed of particles as small as 15 nm in diameter. Conversely, Kendall’s approach is found to predict the Young’s modulus over the full porosity range. Moreover, the adhesion energy in Kendall’s model has to be adjusted to a value of the order of the fracture energy of the particle material. This suggests that sintering during drying leads to the formation of covalent siloxane bonds between the particles. (10.1039/C7SM02443F)
  DOI : 10.1039/C7SM02443F
• Using a discrete element/finite element approach to model impact of a rigid projectile on concrete and reinforced concrete targets
  
  • Antoniou A.
  • Daudeville L.
  • Marin Philippe Maurice
  • Potapov S.
  , 2018, 180, pp.3-14. (10.2495/SUSI180011)
  DOI : 10.2495/SUSI180011
• Similarities between mode III crack growth patterns and strike-slip faults
  
  • Cambonie T.
  • Klinger Y.
  • Lazarus Veronique
  Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Royal Society, The, 2018, 377 (2136), pp.20170392. Why are strike slip faults not perfectly linear but made of successive segments? Are they reminiscences of the fracture of an initially sound crust by the bottom-up propagation of a crack subjected to mode III loading? The plausibility of this newly proposed scenario will be investigated here through model experiments and some theoretical explanations in the framework of brittle fracture. (10.1098/rsta.2017.0392)
  DOI : 10.1098/rsta.2017.0392
• Automotive cylinder heads: recent advances on Thermal-Mechanical Fatigue design and upcoming challenges
  
  • Szmytka Fabien
  • Osmond Pierre
  • Rémy Luc
  • Masson Pierre-Damien
  • Forre Agathe
  MATEC Web of Conferences, EDP sciences, 2018, 165, pp.17003, 6 p.. Through the peculiar case of an automotive cylinder head, actual and forthcoming challenges for low-cycle and thermal-mechanical fatigue design in an industrial context are presented. A special focus is applied on variable loadings, constitutive models and their interaction with the environment, fatigue criteria and structure validations. (10.1051/matecconf/201816517003)
  DOI : 10.1051/matecconf/201816517003
• Crack nucleation in variational phase-field models of brittle fracture
  
  • Tanné E.
  • Li T.
  • Bourdin B.
  • Marigo J.-J.
  • Maurini C.
  Journal of the Mechanics and Physics of Solids, Elsevier, 2018, 110, pp.80 - 99. Phase-field models, sometimes refered to as gradient damage or smeared crack models, are widely used methods for the numerical simulation of crack propagation in brittle materials. Theoretical results and numerical evidences show that they can predict the propagation of a pre-existing crack according to Grith' criterion. For a one-dimensional problem, it has been shown that they can predict nucleation upon a critical stress, provided that regularization parameter be identified with the material's internal or characteristic length. In this article, we draw on numerical simulations to study crack nucleation in commonly encountered geometries for which closed-form solutions are not available. We use U-and V-notches to show that the nucleation load varies smoothly from that predicted by a strength criterion to that of a toughness criterion, when the strength of the stress concentration or singularity varies. We present validation and verifications numerical simulations for both types of geometries. We consider the problem of an elliptic cavity in an infinite or elongated domain to show that variational phase field models properly account for structural and material size e↵ects. We conclude that variational phase-field models can accurately predict crack nucleation through energy minimization in a nonlinear damage model instead of introducing ad-hoc criteria. (10.1016/j.jmps.2017.09.006)
  DOI : 10.1016/j.jmps.2017.09.006
• North-western Mediterranean sea-breeze circulation in a regional climate system model
  
  • Drobinski Philippe
  • Bastin Sophie
  • Arsouze Thomas
  • Beranger Karine
  • Flaounas Emmanouil
  • Stefanon Marc
  Climate Dynamics, Springer Verlag, 2018, 51 (3), pp.1077-1093. In the Mediterranean basin, moisture transport can occur over large distance from remote regions by the synoptic circulation or more locally by sea breezes, driven by land-sea thermal contrast. Sea breezes play an important role in inland transport of moisture especially between late spring and early fall. In order to explicitly represent the two-way interactions at the atmosphere-ocean interface in the Mediterranean region and quantify the role of air-sea feedbacks on regional meteorology and climate, simulations at 20 km resolution performed with WRF regional climate model (RCM) and MORCE atmosphere-ocean regional climate model (AORCM) coupling WRF and NEMO-MED12 in the frame of HyMeX/MED-CORDEX are compared. One result of this study is that these simulations reproduce remarkably well the intensity, direction and inland penetration of the sea breeze and even the existence of the shallow sea breeze despite the overestimate of temperature over land in both simulations. The coupled simulation provides a more realistic representation of the evolution of the SST field at fine scale than the atmosphere-only one. Temperature and moisture anomalies are created in direct response to the SST anomaly and are advected by the sea breeze over land. However, the SST anomalies are not of sufficient magnitude to affect the large-scale sea-breeze circulation. The temperature anomalies are quickly damped by strong surface heating over land, whereas the water vapor mixing ratio anomalies are transported further inland. The inland limit of significance is imposed by the vertical dilution in a deeper continental boundary-layer. (10.1007/s00382-017-3595-z)
  DOI : 10.1007/s00382-017-3595-z
• String/frets contacts in the electric bass sound: Simulations and experiments
  
  • Issanchou Clara
  • Le Carrou Jean-Loic
  • Touzé Cyril
  • Fabre Benoît
  • Doaré Olivier
  Applied Acoustics, Elsevier, 2018, 129, pp.217-228. For particular playing techniques such as "pop" or "slap" in the electric bass guitar, the string collides with frets, producing a percussive sound used in dierent music styles. The string/frets contacts introduce a non-linearity which is investigated both numerically and experimentally in this paper. A physical model, based on a modal description of the string, is implemented with an unconditionally stable scheme. Simulations including a string/structure coupling and the two polarisations of the string are confronted to controlled experiments, showing a good agreement for increasing amplitudes of initial conditions. A parametric study is then conducted numerically in order to highlight the inuence of physical parameters on the transient behaviour and raises questions related to tuning and playing issues. (10.1016/j.apacoust.2017.07.021)
  DOI : 10.1016/j.apacoust.2017.07.021
• Wavefield characteristics and spatial incoherency - a comparative study from Argostoli rock- and soil-site dense seismic arrays
  
  • Imtiaz Afifa
  • Perron Vincent
  • Hollender Fabrice
  • Bard Pierre-Yves
  • Cornou Cécile
  • Svay Angkeara
  • Theodoulidis Nikos
  Bulletin of the Seismological Society of America, Seismological Society of America, 2018, 108 (5A), pp.2839-2853. The current article presents the results from the analysis of the seismic events recorded from a dense array located on a rock site at Argostoli, Cephalonia Island, Greece. The objective of the study is to explore to what extent the non-direct, diffracted surface waves influence the seismic wavefield at a rock site, to investigate the loss of coherency of ground motions and to compare the results with those from a previously studied similar array located at an adjacent small, shallow sedimentary valley. The array consists of 21 velocimeters encompassing a central station in four concentric circles with diameters 20, 60, 180 and 360 m. The analyzed seismic dataset includes 40 events with magnitudes ranging from 2 to 5 and epicentral distance up to 200 km. MUSIQUE algorithm has been used to analyze the seismic wavefield by extracting the backazimuth and slowness of the dominant incoming waves and identifying the Love and Rayleigh waves. Lagged coherency has been estimated for all the available station pairs in the array and the results from the entire dataset have been averaged at four separation distance intervals, 10-20, 20-30, 30-40, 80-90 m. The results were also compared with those from a similar array located on an adjacent small, shallow sedimentary valley. The analysis suggests that about 20percent energy of the wavefield could be characterized as diffracted Love and Rayleigh waves, primarily arriving from the north-east and north-south directions, respectively. The spatial coherency estimations at the rock site are, generally, observed to be larger than those from the sedimentary array, especially at frequencies below 5 Hz. The directionality of coherency estimates observed from the soil array is absent in case of the rock array data. Comparison with the widely-quoted parametric models reveals that there is little correlation between the decay of coherency observed at the rock site and the models. The significant difference observed between the results of the rock and soil array indicate that the spatial incoherency is largely site dependent and could be potentially associated with the formation of locally generated wavefield (10.1785/0120180025)
  DOI : 10.1785/0120180025