Dissertations / Theses on the topic 'Ondes de détonation – Interaction fluide-structure'
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Barras, Guillaume. "Interaction fluide-structure : application aux explosions sous-marines en champ proche." Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10003/document.
Full textIn military shipbuilding, ships are designed to withstand conventional threats such as mines or torpedoes. These designs are based on calculations of structural response to underwater explosions in far field, what is relatively well controlled today. The thematic of underwater explosions has indeed benefited from extensive research since the Second World War. This has resulted in robust numerical methods to simulate the main phenomena that characterize such events. These methods used in engineering are based on assumptions that limit their scope. These restrictions are discriminatory when we attempt to simulate underwater explosions in near field which are mainly nonlinear phenomena. In this context, the Multi-Material Arbitrary Lagrangian-Eulerian method with Euler-Lagrange coupling is chosen to simulate these problems. To make the method more easily applicable in engineering, its adaptation is based on two points. (1) Firstly the method is developed for two-dimensional cases in order to solve 2D axisymmetric problems with higher speed and accuracy compared to 3D simulations. (2) Then the projection of results from two-dimensional analysis on 2D or 3D grids is implemented. The projection from one grid to the other allows solving the whole problem through successive phases for physics on very different time scales and space scales, what necessitates adapted meshes. The developments are implemented in LS-DYNA code for the revised version 5.1.1 and validated for the different phases of the problem from theoretical and experimental results
Chinnayya, Ashwin. "Construction de modèles et de méthodes numériques pour les écoulements multiphasiques à phases compressibles : application à la simulation des ondes de détonation dans les matériaux hautement énergétiques." Aix-Marseille 1, 2002. http://www.theses.fr/2002AIX11066.
Full textMahmadi, Kamal. "Modélisation des phénomènes d'ondes explosives." Lille 1, 2006. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2006/50376-2006-Mahmadi.pdf.
Full textTartière, Jérémie. "Prediction of deformation and residual stress in the high explosive hydroforming process using numerical simulation." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2022. http://www.theses.fr/2022ENTA0008.
Full textBefore the COVID-19 pandemic, Airbus was receiving more and more orders from aircraft, and was hoping, through high explosive hydroforming, to be able to meet more demands. To avoid additional costs for the development of a new technique, numerical simulation is used. However, the time required for calculation and engineering is too long and the accuracy is sometimes insufficient to allow easy integration into the various projects concerned. In addition, the viability of the process for industrialisation must be considered. To meet this need, the various steps related to High Explosive HydroForming are first identified. Firstly, the detonation is studied to allow a better understanding of the energy source acting during explosive forming. Next, the propagation of the shock wave from the underwater explosion is evaluated as well as the fluid-structure interaction in the case of explosive forming as defined within Airbus. Based on these considerations, a «FSILoad» tool, based on a semi-analytical approach, allowing the application of a pressure equivalent to the detonation of explosive cords is created. To ensure the correct definition of the aluminium alloy of which the part is made, this alloy is characterised by quasi-static uni-axial tensile tests, dynamic tests via Hopkinson bars and laser shock. A digital model is created using this new input data. During high explosive hydroforming, the residual stresses resulting from the simulation are compared to the experiment and an analytical model is defined to allow the identification of influential parameters. Finally, the parameters likely to affect the final deformation in simulation are identified, the viability of the FSILoad tool quantified and the repeatability of the process to meet an evaluated industrial need
Gout, d'Henin Emmanuelle. "Ondes de Stoneley en interaction fluide-structure." Poitiers, 2002. http://www.theses.fr/2002POIT2263.
Full textAlia, Ahlem Souli Mhamed. "Simulation numérique en vibroacoustique et en interaction fluide structure." Villeneuve d'Ascq : Université des sciences et technologies de Lille, 2007. https://iris.univ-lille1.fr/dspace/handle/1908/1022.
Full textN° d'ordre (Lille 1) : 3849. Résumé en français. Titre provenant de la page de titre du document numérisé. Bibliogr. p. 151-159.
Alia, Ahlem. "Simulation numérique en vibroacoustique et en interaction fluide structure." Lille 1, 2006. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2006/50376-2006-Alia.pdf.
Full textElhabre, Bou Obeid Marie Louise. "Modélisation de l'intéraction sismique sol-fluide-parois moulées suivant une approche périodique." Châtenay-Malabry, Ecole centrale de Paris, 2000. http://www.theses.fr/2000ECAP0651.
Full textTakahashi, Takéo. "Analyse théorique, analyse numérique et contrôle de systèmes d'interaction fluide-structure et de systèmes de type ondes." Habilitation à diriger des recherches, Université Henri Poincaré - Nancy I, 2008. http://tel.archives-ouvertes.fr/tel-00590675.
Full textFacchinetti, Matteo Luca. "Un modèle phénoménologique des vibrations induites par détachement tourbillonnaire." Palaiseau, Ecole polytechnique, 2003. http://www.theses.fr/2003EPXX0003.
Full textOuld, Abdallahi Mohamed. "Contribution à la mise en place d'une méthode d'intensimétrie à quatre capteurs." Lille 1, 2001. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2001/50376-2001-117.pdf.
Full textRendu, Quentin. "Modélisation des écoulements transsoniques décollés pour l'étude des interactions fluide-structure." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1328/document.
Full textTransonic flows, which are common in aeronautical and spatial propulsion systems, produce shock-waves over solid boundaries. When a shock-wave impacts the boundary layer, an adverse pressure gradient is generated and a thickening or even a separation of the boundary layer is induced. If the solid boundary vibrates, the shock-wave oscillates, interacts with the boundary layer and produce a fluctuation of the static pressure at the wall. This induces an exchange of energy between the fluid and the structure which can be stabilising or lead to an aeroelastic instability (flutter).The main objective of this PhD thesis is the modelling of the unsteady behaviour the simulation of the shock-wave/boundary layer interaction for fluid-structure interaction studies. To this end, simulations have been carried out to solve Reynolds-Averaged Navier-Stokes equations using two equations turbulence model. The method is validated thanks to experimental data obtained on a transonic nozzle dedicated to aeroelastic studies. This method is then use to increase the predictability of flutter events in turbomachinery.A time linearised frequency-domain method is applied to RANS equations. It is shown that the unsteady behaviour of the turbulent boundary-layer contributes to the fluctuating static pressure when the shock-wave boundary layer interaction is strong. Hence, the frozen turbulence assumption is not valid and the turbulence model must be derivated. Thus, the regularisation of the non derivable operators is proposed and applied on k-? Wilcox (2006) turbulence model.The unsteady behaviour of the shock-wave/boundary-layer interaction in a transonic nozzle is evaluated thanks to 2D numerical simulations and shows good agreement with experimental data. When varying the reduced frequency an aeroelastic instability is found, known as transonic flutter. An active control device generating backward travelling pressure waves is then designed and numerically validated.Finally, a methodology is proposed to understand the aerodynamic onsets of transonic flutter. To this end, a preliminary design of a high bypass ratio transonic fan has been carried out. This fan, named ECL5, is dedicated to experimental aerodynamic and aeroelastic studies. The methodology relies on 2D simulations of a tip blade passage and uses linearisation to analyse the contribution of local sources as a function of reduced frequency, nodal diameter and mode shape
Valibouse, Pierre. "Mesure des caractéristiques intrinsèques des matériaux dans l'eau, avec un tube à impédance en incidence normale." Compiègne, 1990. http://www.theses.fr/1990COMPD317.
Full textTerrana, Sébastien. "Méthodes Galerkin discontinues hybridables pour la propagation des ondes élastiques et acoustiques dans des milieux géophysiques complexes." Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC081.
Full textNew seismological monitoring networks combine broadband seismic receivers, hydrophones and micro-barometers antenna. Exploiting these observations requires accurate and multi-physics — elastic, hydro-acoustic, infrasound - wave simulation methods which are able to model the complex energy exchanges at material interfaces. In this thesis, we develop a new Hybridizable Discontinuous Galerkin (HDG) method for solving elastic and acoustic wave propagation, with an arbitrary high order of accuracy in space. In order to introduce this method, we first derive the transmission conditions between heterogeneous elastic, acoustic, and elasto-acoustic media using the Rankine-Hugoniot relations. These conditions are then used to design the inter-element numerical traces in an HDG framework, which make this method able to model both elastic and acoustic waves in the same simulation. We subsequently perform a space discretization using a spectral approach, and we propose a time-scheme able to enforce properly the algebraic transmission equation. The spectral convergence of the method is assessed on both elastic and elasto-acoustic benchmarks, and some validation benchmarks for the PML are performed. Finally we present a more realistic case of coupling between seismic waves and infrasounds
Girault, Gregory. "Réponse d'une plaque couplée à un liquide et soumise à une pression mobile. Aspects théoriques et expérimentaux en détonique." Phd thesis, Université d'Orléans, 2006. http://tel.archives-ouvertes.fr/tel-00091961.
Full textMahmadi, Kamal Souli Mhamed. "Modélisation des phénomènes d'ondes explosives." Villeneuve d'Ascq : Université des sciences et technologies de Lille, 2008. https://iris.univ-lille1.fr/dspace/handle/1908/1160.
Full textN° d'ordre (Lille 1) : 3829. Publications en anglais reproduites en annexe. Résumé en français et en anglais. Titre provenant de la page de titre du document numérisé. Bibliogr. p. 134-144.
Messahel, Ramzi. "ALE and SPH formulations for Fluid Structure Interaction : shock waves impact." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10022/document.
Full textThis thesis focuses on the numerical study of the propagation of shock waves in compressible multiphase flows and fluid structure interaction. Two approaches are being studied for the numerical solution of the fluid part: the ALE approach (Arbitrary Lagrangian Eulerian) and the Lagrangian SPH (Smoothed Particle Hydrodynamics) approach; while the structure part is solved by a conventional FE (Finite Element). The numerical investigation of the ALE and SPH methods are the two main areas of research.Water Hammers phenomena occuring in nuclear industries are investigated in this thesis. During a Water Hammer, the shock waves reflections in nuclear piping may drop locally the water pressure below its saturation pressure and generate cavitation. The three equations HEM (Homogeneous Equilibrium Model) phase change model proposed by Saurel et al. (1999) is studied and applied to solve water hammers. The obtained results are compared with experimental data. Despite the use of renormalization techniques in SPH, instabilities (numerical oscillations) are developed at the interface between particles from different materials. These instabilities restrict the use of traditional SPH schemes to problems with low density ratio. In order to solve the shock problems in the compressible regime, the scheme originally proposed by Hu and Adams (2006) is adapted to fully compressible regime (FC-SPH) by considering the coupling between the density and the smoothing length. The different SPH schemes are compared for 1-D and 2-D multiphase shock problems. Validation is performed in comparison with exact solutions for 1-D problems and ALE solution for 2-D problems
Bhuddi, Ajit. "Approche ondulatoire pour la description numérique du comportement vibroacoustique large bande des conduites avec fluide interne." Thesis, Tours, 2015. http://www.theses.fr/2015TOUR4046/document.
Full textIn this work, a wave finite element (WFE) method is proposed to predict the sound radiation of finite axisymmetric fluid-filled pipes immersed in an external acoustic fluid of infinite extent, The Sommerfeld radiation condition is taken into account by means of a perfectly matched layer (PML) around the external fluid. Within the WFE framework, the fluid-filled pipe, the surrounding fluid and the PML constitute a multiphysics waveguide that is discretized by means of a periodic finite element mesh, and is treated as an assembly of identical subsystems of small length. Wave modes are computed from the FE model of a multi-physics subsystem and used as a representation basis to assess the vibroacoustic behavior of the finite waveguide at a low computational cost. Numerical experiments are carried out in the cases of axisymmetric pipes of either homogeneous or multi-layered crosssections, The accuracy and efficiency of the proposed approach are dearly highlighted in comparison with the conventional FE method
Bénéfice, Guillaume. "Développement d'une méthode de couplage partitionné fort en vue d'une application aux turbomachines." Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0050/document.
Full textTo increase turbomachinery design, manufacturers have to comprehend complex aeroelastic phenomena involving compressors like fluid-structure interaction limit cycles of fans. The understanding and the modeling of these phenomena involve developing complex solvers coupling techniques and validating these techniques with bench tests. The bench test of the CREATE compressor is instrumented to study the coupling between aerodynamic instabilities and structure vibration, in particular on the first stage rotor, and allows to validate numerical techniques. The flow modeling upstream to the first stage with the Turb’Flow flow solver (targeting turbomachinery applications) shows that, to have accurate results, inlet limit conditions must take into account. The ingestion of non-homogeneous flow upstream to the inlet guide vane is accurately modeled. This phenomenon can appear upstream to fans and interact with structure Eigen-modes. Explicit partitioned strong coupling considered in time domain was implemented in a Turb’Flow flow solver. As there is a risk of time shift at the fluid-structure interface, careful attention should be paid to energy conservation at the interface. This conservation is crucial when displacements are large and when strong non-linear behaviors occur in both fluid and structure domains, namely shock waves, flow separations and non-linear structural damping. In parallel with coupling technique development, the three-order implicit Runge-Kutta scheme (RKI-3) was implemented and validated on a structure dynamic case (transonic turbine blade vibration) and on a case of shock waves propagation. The RKI-3 scheme allows increasing the time step of one order of magnitude with the same accuracy. There is a CPU time gain for structure dynamics simulations, but no for URANS simulations. However, the RKI-3 scheme can be to use for fluid-structure coupling simulations. The coupling technique was validated on a test case involving tube in which the shock wave impinges on a cross flow flexible panel, initially at rest. This case allows modeling an interaction between sonic flow and a panel movement with a tip clearance. Some numerical simulations were carried out with different temporal schemes. The RKI-3 scheme has no influence on results (compared with Gear and/or Newmark scheme) on the energy conservation at the fluid-structure interface. Compared to experimental results, pressure is in fairly good ix Liste des publications agreement. The analysis of numerical results highlighted that a vertical shock tube with up and down waves creates pressure fluctuation. Frequency is under predicted and amplitude is not in fairly good agreement. The panel root modeling might be questionable
Fritsch, Jean-François. "Propagation des ondes dans les guides partiellement enfouis : résolution du problème direct et imagerie par méthode de type échantillonnage." Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAE001.
Full textThis work is about the non destructive testing of partially buried or immersed slendered structures such as a steel cable partially buried in concrete or a steel plate partially immersed in liquid sodium. Such structures can be seen as the junction of two closed waveguides. In order to perform computing, the open part of the structure is truncated in the transverse direction with PMLs. As a result, a partially buried waveguide can be treated as the junction of two closed waveguides, in one of which the propagation of waves is governed by an equation involving complex coefficients due to the presence of the PMLs. This observation has lead us to tackle first the simpler case of the junction of two closed acoustic waveguides. For this simple case, we have proposed a strategy to solve the inverse problems based on the one hand on the introduction of the so-called reference fields, which are the total field response of the structure without defects to an incident field coming frome both half-guides, and on the other hand on the use of the reciprocity of the Green function of the structure without defect. Following this strategy, we have obtained an efficient modal formulation of the LSM which has enabled us to retrieve defects. In this simple case, we have taken advantage of the completeness of the modes to analyze the forward and inverse problems. The loss of the completeness of the modes in the half-guide truncated in the transverse direction with PMLs has led us to study the forward problem with Kondratiev theory. The tools introduced for the junction of two closed waveguides have been adapted to solve the inverse problem. Finally, we have tackled the more complex, but more realsitic case of an elastic waveguide partially immersed in a fluid. For this difficult case, we have developped adapted computing tools adapted and extended the tools introduced before solving the inverse problem
Philit, Mickaël. "Modélisation, simulation et analyse des instationnarités en écoulement transsonique décollé en vue d'application à l'aéroélasticité des turbomachines." Thesis, Ecully, Ecole centrale de Lyon, 2013. http://www.theses.fr/2013ECDL0033/document.
Full textIn modern turbomachinery design, predicting aerolastic phenomena has become a key point. The development of highly loaded components, while reducing their weight, increases the risk of failure. In this context, good understanding and prediction of various instabilities are a major industrial and scientific challenge. This research work aims to improve the prediction of unsteady phenomena involved in turbomachinery aeroelasticity. This study focuses especially on the simulation of shock wave/boundary layer interaction. To begin with, a transonic nozzle separated flow is investigated. Forced oscillation of the shock wave system is simulated through a small unsteady perturbation method combined with the assumption of variable turbulence. This approach is validated against exprimental measurements. The first harmonic of pressure on the wall of the nozzle is predicted quite satisfactorily. The need to linearize the turbulence model was shown of high importance. Deriving the turbulence model, leads us to investigate the turbulence modeling performed to predict the shockwave/boundary layer interaction. A two equations turbulence model supplemented by a "time-lagged" equation is implemented to capture non-equilibrium effects of turbulence. All achieved results for a nozzle are consistent with theory, but overproduction of turbulent kinetic energy at leading edge makes the model useless for turbomachinery configurations. However, the introduction of an eddy viscosity stress limiter inside a two-equation turbulence model proves to give good results. The derivation method is thus presented on such a model, precisely on Wilcox model proposed in 2008. Finally, the linearization technique is extended to aeroelastic problems. A loose fluid-structure coupling strategy is adopted. The structural oscillation of the blades is considered for eigen-modes but frequency is free to change during coupling resolution. The new approach is based on the building of a meta-model to describe the fluid dynamic behavior in order to solve directly the coupled fluid-structure system. This technique is validated on a standard high subsonic turbine configuration and takes advantage of a reduced computation time
Peronne, Simon. "Modélisation expérimentale et analyse spatio-temporelle de l'hydrodynamique de la zone de déferlement à la zone de swash." Caen, 2010. http://www.theses.fr/2010CAEN2064.
Full textA study on the dynamics of the free surface and flow from the surf zone to the swash zone is proposed, based on results obtained from an experimental model in wave flumes, monitoring Lagrangian of the free surface and Eulerian measurements of the internal flow. After an inventory of results related to this area, a first part is devoted to the description of measuring systems, validation of measurement tools in this area and the presentation of the possible swells scenarios. Secondly, the use of algebraic and analytic tools in data processing is described and justified. A method for extracting the bore velocity from the surf zone from video measurements is also presented. The analytical work is divided into four stages. An analysis of the characteristics of the bore in the surf zone is proposed based on the video measurements. Then, the generation and eventual release of secondary waves (high or low frequencies) from non-linear processes, through different approaches classical and original, is treated. A comparison between the secondary wave generation and the dissipation of the potential energy is proposed and a study on wave pairing is also written. Thus, the internal flow in the transition zone between the inner surf zone and swash zone is studied to describe the interactions between offshore currents generated during the backwash phase and incident bore. Finally, after an analysis of boundary conditions in the inner surf zone, the last part is devoted to the study of the flow in the swash zone and the related bottom shear stress and friction factor
Biamino, Laurent. "Etude expérimentale de l'interaction d'une onde de choc avec une structure mobile autour d'un axe." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10093/document.
Full textThis thesis is based on an experimental study carried out in shock tube; in particular, this is an experimental approach to the study of fluid-structure interaction. Consider a rigid body which is allowed to rotate only around an axis and which closes a confined space. If a shock wave crosses the content of the confined space, the body will accelerate and rotate around its axis. Specifically, the shock wave will increase the physical characteristics, especially its pressure, of the fluid acting on the impacted face of the door. The opposite side of the door is not influenced by the incident shock wave, only one of its faces is subjected to overpressure. Following the first impact, the resulting imbalance imposes a mechanical action on the door that will increase its speed and make it turn around its rotation axis. The difficulty comes when the door begins to open: the volume boundaries in which the fluid is contained are modified. Leaks occur and the gas kept in this closed volume can now flow to the atmosphere. Communication between the gas acting on each side of the door is created modifying their properties and consequently the pressure acting on each side of the door.The mechanical actions that apply to the door are no more the same with time, and therefore the acceleration of the door is changing. As the door moves, the fluid problem continues to be changed and in turn it changes its action on the door. This interaction process continues until either the limits of the problem ceases to be changed, the door cannot move, or when the mechanical actions acting on the door are in equilibrium, fluids on each side of the door are in the same physical state. The presented work is a study of the parameters of the fluid or the solid motion which are main actors in the behavioral law managing this complex system. In this aim, we designed an experimental device involving the physics that we have described and we have adapted it to a shock tube. Testing many experimental configurations, we could determine how the internal flow of a shock tube evolves when the end of this shock tube is more or less open.How a closed door reacts to the impact of a shock wave and what are the implications for the evolution of the involved fluids? What are the consequences of a different position of the door at the instant of the impact with the incident shock wave? What role plays the intensity of the incident shock wave or the inertia of the door on this dynamic?
Coudouel, Guillaume. "Toward a numerical predictive method based on fatigue analysis for droplet impingement erosion." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI101/document.
Full textThe goal of this work is the comprehension and the numerical simulation of erosion caused by repeated droplet impact on Pelton turbine buckets, to predict the lifetime of these components. First, waves propagation phenomenon inside fluid and solid domains are presented, which allows determining the time evolution and spatial distribution of contact pressure, and the birth of lateral microjets by supersonic ejection of the fluid on the contact. Experimental studies of erosion by droplet impact highlight a fatigue cracking-based erosion mechanism. Then, coupled FSI computation are performed. The solid subdomain is discretized by the Finite Element Method (FEM), and the fluid subdomain by the Smoothed Particle Hydrodynamics (SPH), which is a particle method (meshless) effectively recommended for large distortions and free surface tracking. Stress analysis confirms the cyclic nature of the damage mechanism, and erosion simulation is performed using multiaxial fatigue criteria. The first selected criterion is a general one from the American Society of Mechanical Engineers (ASME) using principal values of stress differences over time. The second one is the Dang van 2 criterion, belonging to the family of critical plane criteria. This criterion considers separately the effects due to hydrostatic stress on one hand, and the ones induced by maximum local shear on the other. These two criteria are used to building the equivalent eroded zones of the solid subdomain for a given number of impacts, which allows to qualify this procedure as a predictive predictive. Finally, a parametric study for different droplet sizes and velocites is computed, and the effects of a coating layer are investigated
Jean, Philippe. "Une méthode variationnelle par équations intégrales pour la résolution numérique de problèmes intérieurs et extérieurs de couplage élasto-acoustique." Compiègne, 1985. http://www.theses.fr/1985COMPD012.
Full textOtsuka, Masahiko. "Applications effectives de l'onde de choc hydrodynamique générée par pulsation électrique ou par explosion." Lille 1, 2007. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2007/50376-2007-9.pdf.
Full textA choc wave generated by an underwater explosion or electric pulsed power can be used for industrial applications. Ln automotive and aerospace industry, sheet metal forming is usually used for parts production. Ln metal forming we usually encounter numerical difficulties as spring back problems, which requires implicit time integration, since the time for the structure to damp out from high frequency vibrations is long compare to loading time. Metal forming has a high cost for industrial applications. . Pressure loading due to the press machine in metal forming can be generated through pressure waves from detonation points in hydrodynamic medium. The aim of this work, which has an experimental part, that is validated by numerical simulation, consists of generating pressure waves for dynamic problems, through discrete detonation points, at different locations and detonating at different detonation time. Pressure waves from detonation create a structure loading similar to the one created by the press machine in metal forming. The problem is a fluid structure interaction problem, where the fluid has high damping properties compare to those of ambient air. The fluid is solved using compressible Navier-Stokes equations with equation of state relative to explosive material, the structure is solved with structural dynamic equations, using explicit time integration
George, Sijo. "Simulation numérique directe de la transition laminaire turbulent sur un hydrofoil flexible." Thesis, Ecole centrale de Nantes, 2021. http://www.theses.fr/2021ECDN0010.
Full textThe laminar to turbulent transition induced vibration over a NACA66 hydrofoil at Re = 450000 is investigated in this thesis. DNS is used to simulate the 3D incompressible boundary layer flow, and it is coupled with a freely pitching hydrofoil. An implicit coupling is developed within the fluid solver Nek5000. A number of cases are performed to validate this method, which lead to study the transition induced vibration. Then, a parametric study consisting of two forced and three free oscillations allowed analyzing the interactions between the vibration and the boundary layer transitional flow. A set of specific non-dimensional parameters are set, which aim at characterize the fluid structure interactions in such flow regime. From the boundary layer flow analysis, it was observed that the spatial location of the transition point is proportional to the amplitude of pitch, velocity, and frequency ratio. The generation of TS waves (the first stage of laminar to turbulent transition) is also influenced by the vibrations. It was also observed that the span wise wavelength of coherent structures (so called “hair-pin” structures” that form downstream of the TS waves) is proportional to the displacement thickness. The spatial advancement of the transition point reduces the amplitude of periodic pressure fluctuations in the transition regime. In addition, the length of the transition region is increased. Finally, a multi-scaled frequency response is observed due to the enhanced interaction between transition and pitch oscillation when the transition and natural frequencies are close to each other. The study suggests that in this case, the fluid structure interaction tends to disturb the spatio-temporal behavior of laminar to turbulent transition. Although it has to be confirmed, this phenomenon has already identified experimentally through measurements performed at the Naval Academy Research Institute (IRENav) in hydrodynamic tunnel for a higher Reynolds number case
Graja, Fatma. "Influence des conditions d'interfaces d'un milieu poreux saturé sur la propagation des ondes ultrasonores : analyses acoustique et diélectrique." Thesis, Le Mans, 2017. http://www.theses.fr/2017LEMA1032/document.
Full textThis work is part of a collaboration between the University of Sfax and the University of Maine. The thesis entitled "Influence of the interface conditions of a saturated porous medium on the propagation of ultrasonic waves: acoustic and dielectric analysis". The work presented in this dissertation examines theme chanisms that can be reproduced in a porous medium saturated by an incompressible fluid when subjected to a pressure gradient for the acoustic studyand an electromagnetic field gradient for the dielectricstudy. Consequently, the present paper is interested in presenting two techniques of characterization:i) Acoustic characterization where Biot's theory was adopted to understand the mechanisms of propagation of ultrasonic waves in saturated porous materials and to study the influence of changing interface conditions onreflection and transmission coefficients. The presence of a flat defect in the volume of the material has be entreated. The study of the influence of the presence of several spherical inclusions on the modification of the lines of velocity fields was presented by proposing a model of tortuosity adapted according to the nature of the inclusion and the porous medium host (homogeneityand anisotropy).ii) The dielectric analysis which allows to describe the internal structure and the interaction between the solidand the saturating fluid. Dielectric measurements were carried out on porous silica ceramics identical to thoseused in ultrasonic characterization in order to study the influence of the state of the lateral surfaces of the sample on the interaction between the saturating fluid and the surfaces of the porous structure.The results make it possible to demonstrate an analogy between the behavior of the inclusion in the velocity field of the fluid and that of a dielectric sphere in a uniformelectric field. Acoustic experiments and dielectric measurements (spectroscopy) were carried out and compared with numerical simulations and theoretical models in both parts of the study
Berbiche, Amine. "Propagation d'ondes acoustiques dans les milieux poreux fractals." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4758.
Full textThe action integral minimization method (variational principle) provides the wave propagation equations. This method has been generalized to fractal dimensional porous media to study the acoustic propagation in the time domain, based on the equivalent fluid model. The resulting equation rewritten in the frequency domain represents a generalization for the Helmholtz equation. As part of the Allard-Johnson model, the propagation equation was solved analytically in the time domain, for both high and low frequencies fields. The resolution was made by the method of the Laplace transform, and focused on a semi-infinite porous medium. It was found that the wave velocity depends on the fractal dimension.For a fractal porous material of finite thickness which receives an acoustic wave at normal incidence, the Euler conditions were used to determine the reflected and transmitted fields. The resolution of the direct problem was made in the time domain by the method of the Laplace transform, and through the use of the Mittag-Leffler functions. The inverse problem was solved by the method of minimizing the least squares sense. Tests have been performed successfully on experimental data; programs written from the formalism developed in this work have allowed finding the acoustic parameters of porous foams, in the fields of high and low frequencies
Szubert, Damien. "Physics and modelling of unsteady turbulent flows around aerodynamic and hydrodynamic structures at high Reynold number by numerical simulation." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/15129/2/szubert_1.pdf.
Full textHadžalić, Emina. "Analysis of pore pressure influence on failure mechanisms in structural systems." Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2502.
Full textThis thesis studies the issue of the overall safety of structures built of heterogeneous and pore-saturated materials under extreme loads in application to fluid-structure interaction problems, such as the dam-reservoir interaction. We propose a numerical model of interaction capable of predicting main tendencies and overall behavior of pore-saturated dam structure interacting with the reservoir in failure analyses of practical interest. The proposed numerical model is first presented in two-dimensional (2D) framework and later extended to three-dimensional (3D) framework. We consider the structure built of porous cohesive material. We assume that the external fluid in interaction with the structure acts as a source of pore saturation. We model the response of the pore-saturated structure with the coupled discrete beam lattice model based on Voronoi cell representation of domain with inelastic Timoshenko beam finite elements enhanced with additional kinematics in terms of embedded strong discontinuities acting as cohesive links. The coupling between the solid phase and the pore fluid is handled with Biot’s porous media theory, and Darcy’s law governing the pore fluid flow. The numerical consideration of internal coupling results with an additional pressure-type degree of freedom placed at each node of the Timoshenko beam finite element, which is later used at the fluidstructure interface. The confined conditions met for external fluid placed in the reservoir enable the modeling of external fluid motion with the acoustic wave theory. For the numerical representation of the external fluid limited to small (irrotational) motion, we choose a Lagrangian formulation and the mixed displacement/pressure based finite element approximation. The end result are the displacement and pressure degrees of freedom per node of external fluid finite elements, which allows for the issue of the fluid-structure interface to be solved in an efficient and straightforward manner by directly connecting the structure and external fluid finite elements at common nodes. As a result, all computations can be performed in a fully monolithic manner. All numerical implementations and computations are performed with the research version of the computer code FEAP (Finite Element Analysis Program). The proposed numerical models of structure, external fluid and ultimately numerical model of interaction are validated in the linear elastic regime of structure response by comparing computed results against reference values obtained either with analytical solutions or continuum models. The numerical simulations in the nonlinear regime of structure response are performed with the aim to demonstrate the proposed coupled discrete beam lattice model capabilities to capture complete macro-scale response and failure mechanisms in pore-saturated structures. Finally, the proposed numerical model of interaction ability to deal with the progressive localized failure of a dam structure built of porous cohesive material under damreservoir interaction for a particular loading program was tested. To account for the temperature effects, the thermal coupling is introduced in the numerical model of the structure