Dissertations / Theses on the topic 'Rayonnement acoustique d'un turboréacteur'
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Duprey, Stefan. "Etude mathématique et numérique du rayonnement acoustique d'un turboréacteur." Nancy 1, 2006. https://tel.archives-ouvertes.fr/tel-00145205.
This thesis deals with the industrial problem of modelisation and numerical simulation of the acoustic radiation from fan duct air entry. The physical hypothesis subsequent to the industrial framework give way to a simplified model of linear acoustic propagation upon a non linear potential flow. Engine modal noise source modelisation requires acoustic boundary conditions through a Dirichlet-Neumann operator. Existence and uniqueness of the global mathematical problem (a convected Sommerfeld condition is added) of the potential and local perturbation from a uniform flow are prooved. A discrete coupling between the volumic acoustic potential (finite volumic elements) and its elliptic normal derivate (boundary finite element) through an integral equation is exhibed. Computing code is validated analytically and comparatively. Original results are described and prove the necessity to consider the nonlinearity of the flow by differences greater than 5 dBs in the far field acoustic diagrams. Optimal positionning of the radiating surface and the plugability of the fast multipole method make this coupling unmissable. Simplified potential-linear model, even if its range of validity is restricted to the fan duct air entry, gets his whole interest as a brick in a global domain decomposition code. By the way, lets mention the achievement of a natural axisymetric finite element and an alternative method to the calculus of the non linear flow by a fixed point method
Duprey, Stefan. "Etude mathématique et numérique de la propagation acoustique d'un turboréacteur." Phd thesis, Université Henri Poincaré - Nancy I, 2006. http://tel.archives-ouvertes.fr/tel-00145205.
la simulation numérique du rayonnement acoustique à l'entrée d'air des nacelles
d'Airbus. Les hypothèses physiques subséquentes au contexte industriel
précis conduisent à un modèle simplifié de propagation acoustique linéaire sur
un écoulement porteur potentiel et non-linéaire. La modélisation de la source
modale de bruit du moteur se traduit par une condition de bord exprimée par
un opérateur Dirichlet-Neumann. L'existence et l'unicité du problème mathématique
général (auquel on a rajouté une condition de Sommerfeld convectée)
de la perturbation potentielle et locale autour d'un écoulement uniforme sont
démontrées. Un couplage discret alliant le potentiel acoustique (éléments finis
de volume) et sa dérivée conormale de bord (éléments finis de frontière) par une
équation intégrale est proposé. Le code informatique est validé analytiquement
et comparativement. Les résultats originaux prouvent la nécessité de la prise en
compte des non-linéarités de l'écoulement par des différences de plus de 5 décibels
en champ lointain. Le positionnement optimal de la surface rayonnante et
la possibilité d'adaptation de la méthode multipôle rapide rendent ce couplage
incontournable. Le modèle simplifié potentiel-linéaire, même si il n'est a priori
apte qu'à traiter l'entrée d'air, trouve toute sa justification en tant que brique
d'un code global basé sur la décomposition de domaine. Finalement, soulignons
l'avènement d'un élément fini axisymétrique naturel et d'une alternative originale
de calcul de l'écoulement non-linéaire par une méthode de point fixe.
Marchner, Philippe. "Non-reflecting boundary conditions and domain decomposition methods for industrial flow acoustics." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0094.
This PhD project is devoted to non-overlapping Schwarz domain decomposition methods for the resolution of high frequency flow acoustics problems of industrial relevance. Time-harmonic solvers are difficult to parallelize due to their high-oscillatory behaviour, and current solvers quickly reach an upper frequency limit dictated by the available computer memory. Non-overlapping Schwarz methods split the domain into subdomains at the continuous level and provide a suitable setting for distributed memory parallelization. The problem is solved iteratively on the interface unknowns, where the keystone for quick convergence relies on appropriate transmission conditions. The first part of this thesis is devoted to the design of transmission operators tailored to convected and heterogeneous time-harmonic wave propagation. To this end we study two non-reflecting boundary techniques that provide local approximations to the Dirichlet-to-Neumann operator. On the one hand, Absorbing Boundary Conditions are designed based on microlocal analysis and pseudodifferential calculus. On the other hand, the convected acoustic stability issue is addressed for Perfectly Matched Layers in convex domains with Lorentz transformation. The second part of this thesis describes how to adapt a generic domain decomposition framework to flow acoustics, and applies the newly designed transmission conditions to simple academic problems. We explain the relation between the non-overlapping Schwarz formulation and an algebraic block LU factorization of the problem. Finally we propose a parallel implementation of the method and show the benefit of the approach for the three-dimensional noise radiation of a high by-pass ratio turbofan engine intake
Lidoine, Stéphane. "Approches théoriques du problème du rayonnement acoustique par une entrée d'air de turboréacteur : Comparaisons entre différentes méthodes analytiques et numériques." Ecully, Ecole centrale de Lyon, 2002. http://www.theses.fr/2002ECDL0029.
Faure, Baldrik. "Caractérisation du rayonnement acoustique d'un rail à l'aide d'un réseau de microphones." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00721959.
Druon, Yann. "Etude de la propagation guidée et du rayonnement acoustiques par les conduits d'éjection de turboréacteur : Modélisations analytiques et numériques." Ecully, Ecole centrale de Lyon, 2006. http://www.theses.fr/2006ECDL0002.
This work deals with the modeling of the acoustic propagation inside turbofan exhaust ducts and the corresponding radiation to the outside. The main objectives are, first, to develop analytical methods, enabling fast and flexible simulations of the problem, and second, to assess the relevance of different numerical methods, now indispensable to account for more realistic geometries and aerodynamic conditions. The study is performed following a progressive process, beginning with simplified configurations to integrate the elements of physical complexity one by one (presence of acoustic liners, realistic geometry, uniform and non-uniform mean flows…). At each stage, the results of the different methods are compared and the influence of the principal parameters is analyzed. The reference solution is given here by an analytical method based on the modal theory for annular ducts with constant cross section. The far field radiation is calculated, in the case of a hub truncated at the exit plane, using the flanged duct approximation, and for an infinite hub, with the aid of the Wiener-Hopf technique. In this last model, the possibility of vortex shedding from the duct trailing edge is included by application (or not) of a Kutta condition. At low frequency, and in the absence of mean flow, the Boundary and the Finite Element Methods (BEM and FEM) give the same results. The comparisons with measurements are also very good, confirming the relevance of the theoretical models. In the presence of a uniform mean flow, the BEM and the FEM respectively tend to the analytical solutions obtained with and without the Kutta condition imposed at the edge. The particular behavior associated to each method is thought to be related to the acoustic variable considered in the codes, i. E. Acoustic pressure or potential. At high frequency, the results of the Gaussian Beam Summation approach are found to be unsatisfactory, probably because of the absence of any diffraction model in the current code formulation. Several geometrical factors influence the acoustic propagation in the secondary exhaust duct (By-Pass). The most critical point lies in the presence of two bifurcations that induce modal redistributions increasing with the rotation of the incident wave inside the duct. An analytical model for sound propagation in a bifurcated duct is presented and validated by comparison with BEM results. Outside the ducts, the influence of the pylon and the after-body real geometry on the radiation to the ground seems to be more limited. Conversely, the effect of shear layers generated at the duct trailing edges is significant. In spite of theoretical restrictions, the waves refraction due to flow mismatches across a vortex sheet (Munt’s model) seems to be relatively well predicted by the FEM potential formulation. The impact of density or temperature gradients, however, is not well reproduced
Dérogis, Philippe. "Analyse des vibrations et du rayonnement de la table d'harmonie d'un piano droit et conception d'un système de reproduction du champ acoustique." Le Mans, 1997. http://www.theses.fr/1997LEMA1012.
Hilbrunner, Olivier. "Développement et optimisation d'un système de contrôle actif pour les absorbants acoustiques hybrides." Ecully, Ecole centrale de Lyon, 2003. http://bibli.ec-lyon.fr/exl-doc/ohilbrunner.pdf.
In order to increase the frequency band of absorption of usual porous materials, the "Centre Acoustique du LMFA" works on the design of hybrid materials using passive and active absorption. The basic principle consists in vanishing by active control the pressure at the rear face of the material, with well-suited characteristics, to achieve a maximum absorption. This thesis deals with the optimisation of the active part, which means a design of a powerful secondary source, including vibroacoustic coupling from the cavities and the effect of wiremesh and the implementation of a digital feedback diagonalised IMC control algorithm. An experiment using four independent cells proves the good functioning of the controller in a duct with flow : very important noise reductions were achieved in the low frequency band
Laulagnet, Bernard. "Rayonnement acoustique des coques cylindriques, finies raidies, revêtues d'un matériau de masquage." Lyon, INSA, 1989. http://www.theses.fr/1989ISAL0035.
RIFAI, SAID. "Etude du rayonnement acoustique d'un obstacle cylindrique place dans un ecoulement d'air subsonique." Poitiers, 1989. http://www.theses.fr/1989POIT2280.
Méry, Fabien. "Instabilités linéaires et rayonnement acoustique d'un écoulement sur une paroi présenatant une cavité." Toulouse, ISAE, 2010. http://www.theses.fr/2010ESAE0017.
Thisse, Johan. "Prévision du bruit d'onde de choc d'un turboréacteur en régime transsonique par des méthodes analytiques et numériques." Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0054/document.
Whereas the sound radiated from the inlet of turbofans is mainly due to rotor–stator interactions in approach flight, the shock waves (or N-waves) emitted by the rotor at transonic rotation speeds can be a dominant noise source during takeoff and climb. The study of N-waves needs to take account of two main processes: 1) the generation of N-waves for a perfect rotor (in which all blades are identical) and for a real rotor (considering small geometrical blade dispersion), and 2) the N-wave propagation through the inlet duct producing the blade passing harmonics for a perfect rotor, and the multiple pure tones (harmonics of the rotation frequency) for a real rotor. Several analytical and numerical approaches have been investigated for the past 40 years.This thesis first intends to relate the main propagation theories and to address the foremost MPT generation method hypotheses. The links between fluid dynamics equations and practical non-linear theories currently adopted are emphasized and discussed. In a second step, the main relevant semi-analytical methods are cross-checked by applying them to representative turbofan configurations. Moreover, a novel model of irregular N-wave generation based on geometrical considerations is investigated thanks to test data related to in-duct pressure signatures and blade stagger angle measurements during the engine operation. Then, a second part of the work investigates a numerical strategy based on elsA ONERA code, solving the full Euler’s equations (CAA approach). The objective is to prevent from the limitations of 2D analytical models and to take into account actual inlet geometry and realistic convection flow. Regular and non-regular shock waves are directly injected in a plane close to the fan and propagated through the inlet. These shock waves are injected through a non-reflective boundary condition which requires the conservative field. The initial shock description near the fan is provided either by a RANS computation or by experiment, or else from analytical model. As experiment or analytical signals only provide pressure signatures, a theory is set up to re-built the whole conservative field from the basis of a pressure shockwave. This injection method is firstly applied on an infinitely narrow annular duct and validated through the comparison with the McAlpine & Fisher analytical method. Then, the 3D propagation effects are pointed out by increasing the duct height. Finally, the CAA method is applied on actual intake geometry of modern turbofan demonstrators, and propagation of regular and irregular shock-waves are simulated. The numerical results are compared to RANS solutions and to available measurements
Ben, Tahar Mabrouk. "Formulation variationnelle par équations intégrales pour le rayonnement acoustique en présence d'un écoulement non-uniforme." Compiègne, 1991. http://www.theses.fr/1991COMPE098.
Mechiche, Alami Omar. "Influence de la houle sur le rayonnement acoustique a tres basse frequence d'un corps sous-marin." Paris 6, 1992. http://www.theses.fr/1992PA066249.
Gavelle, Noël. "Simulation des grandes échelles pour la prévision du rayonnement acoustique d'un jet à grand rapport d'aspect." Paris 6, 2005. http://www.theses.fr/2005PA066205.
Lai, Lu. "Contribution à la mise au point d'un moyen expérimental en vue d'étudier le rayonnement acoustique par une entrée d'air en présence d'un écoulement non uniforme." Compiègne, 1994. http://www.theses.fr/1994COMPD718.
Sanalatii, Maryna. "Synthèse d'un champ acoustique avec contraste spatial élevé." Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1005/document.
The goal of this thesis is the design of a transportable speaker system, able to generate a predefined and focused sound field with a high spatial contrast. This system has eventually to allow carrying out different types of studies, for example acoustic transmission loss tests or vibration tests in non-anechoic conditions. The minimization of the number of driven channels and the number of transducers is one of the main goals of the work. The choice of the number of sources and the selection of their optimal positions in order to generate a target acoustic field has no trivial solution. To answer this question, the proposed method is based on the decomposition of the source radiation into a series of independent orthogonal functions (the "radiation modes"), constructed numerically via a singular value decomposition of the impedance matrix. By filtering the evanescent terms, the far field can be reconstructed using a small number of terms. In addition, the method allows the estimation of an efficient flow distribution to generate the target field. With the proposed method having been scarcely studied in the literature, the first part of the thesis is devoted to the problem of the experimental validation of the direct method and the study of the main parameters that are influencing the result. The problem of sources positioning in order to synthesize a predefined and focused sound field is discussed in the second part of the thesis
Roggerone, Vincent. "Caractérisation du rayonnement acoustique d'un haut-parleur monté sur une enceinte parallélépipédique allongée. Application a une barre de son." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX005/document.
The radiation from a loudspeaker mounted on a box shaped enclosure is usually characterized by measurements or simulations based on finite element method. However, these reference methods are still very expensive and do not allow for a physical interpretation of the results. In this manuscript, two analytical models are proposed to predict this radiation, within the framework of the application to a sound bar. The first model consists of assimilating the sound bar geometry to a spheroid. In this way, the variables are separated and an analytical solution can be found in the form of a sum of spheroidal harmonics. The calculation for a circular loudspeaker on the spheroid, as well as a harmonic truncation criterion, is detailed. Each step of the method will be described, as well as the comparison of the results with the reference methods. The calculation for a circular loudspeaker on the spheroid and the implementation of a harmonic truncation criterion will be developed. This model works well at low-frequency, but cannot account for the diffraction phenomena, which come from the enclosure and appear at high-frequency. Therefore, we have developed a second analytical model based on an integral formulation of the diffraction. This model is seen as a set of secondary sources located on the edges of the enclosure. It will be shown how to establish this model and how it can be implemented. This model allows us to interpret the radiation of a sound bar, and therefore allows us to conclude on the validity of the spheroidal model. It also shows how the baffle edges of a loudspeaker enclosure lead to constructive interference effects, resulting in a gain up to 3 dB. These effects also lead to a counterintuitive phenomenon: if the speaker is not centered on the baffle, the direction of maximum radiation intensity tends to shift to the opposite side of the speaker offset on the baffle
Ekeom, Didace. "Modélisation par la méthode des éléments finis du rayonnement d'un transducteur piézoélectrique dans un puits de forage." Lille 1, 1997. http://www.theses.fr/1997LIL10051.
Skalli, Housseini Aniss. "Développement d'un outil de simulation basé sur le lancer de faisceaux pour la prédiction du bruit intérieur et du rayonnement extérieur des nacelles." Mémoire, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/6611.
Caulkins, Terence. "Caractérisation et contrôle du rayonnement d'un système de Wave Field Synthesis pour la situation de concert." Paris 6, 2007. http://www.theses.fr/2007PA066679.
Mallaroni, Bastien. "Relation entre la géométrie d'un résonateur de longueur finie et son rayonnement : Etude numérique et expérimentale de ses résonances complexes." Aix-Marseille 1, 2010. http://www.theses.fr/2010AIX11122.
The principal goal of this work was to develop a numerical method to study the coupling between internal and external fluid of a resonator, notably to study the link between the shape of a finite length resonator and his radiation. For this we study complex resonances, corresponding to the poles of the Green's function of system coupled with the external environment. The imaginary part of resonance frequencies is here directly related to losses due to radiation. We based our work on three main areas: an analytical study using a modal theory with the inclusion of non-planar modes, the development of a numerical method based on boundary finite elements and an experimental comparison of our theoretical results. The analytical modal theory has allowed us to study the radiation of finite length cylindrical pipe opening into an infinite screen, which is a reference case for further study. The numerical method, developed in a FORTRAN parallelized code, gave us the opportunity to study resonators with more complex geometries such as horns. To reduce computation time, we introduced an hybrid method mixing modal theory to describe the conservative part of system, that allows fast computation, and boundary element method, allowing a fine representation of complex geometries, to describe the radiating part. We have finished this work with a first experimental validation of results
Mathon, Olivier. "Controle de la structure temporelle d'un faisceau synchrotron par des optiques x." Paris 11, 2000. http://www.theses.fr/2000PA112337.
TUCOULOU, TACHOUERES REMI. "Modulation spatiale et temporelle d'un faisceau de rayons x par interaction avec des ondes acoustiques de surface." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10273.
Zhang, Yuwen. "Excitation des ondes élastiques au sein d'un demi-espace anisotrope à l'aide des transducteurs interdigites : Application au quartz et au niobate de lithium." Besançon, 1988. http://www.theses.fr/1988BESA2034.