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Résolution numérique de l'équation de Lighthill par éléments finis et équations intégrales pour l'estimation du bruit rayonné par des écoulements en conduite

Abstract : This thesis is part of the CISSCOH project (Caractérisation et Identification des Sources Sonores dans les Composants Hydrauliques - Determination and identification of sound sources in hydraulic components) supported by the Picardie region and bringing together industrial (CETIM and Poclain Hydraulics) and academic (UTC) partners. Its purpose is the development of numeric calculation tools in order to estimate levels of sound emitted and localize their origin during the design phase of hydraulic components. Our work is more particularly focused on the sound emitted in a duct, created by the interaction between the fluid flow and an obstacle placed in the duct. This interaction creates turbulences which are source of sound. In order to determine the acoustic pressure field created and propagated in the duct, we build upon the Lighthill analogy, formulated in 1952. A calculation chain meant to estimate this pressure is developed around two main steps: calculation of the source field (Lighthill tensor) and propagation of the pressure generated by the sources For the estimation of the acoustic pressure field, two classical numeric methods are developed: a finite elements discretization method and a method based upon the integral formulation of the Lighthill equation. An innovative - hybrid - method is designed from these two classical methods, in order to combine the respective advantages of both: the accuracy of the finite elements and the quickness of the integral method. The calculation chain based on this hybrid method is validated with simulations made on a model similar to a study available in literature. Finally a test bench developed during previous studies at the Roberval laboratory is used to obtain results on an air flow in a rectangular duct in which is inserted a diaphragm. These tests allowed the study of the impact of parameters - like air flow speed and the presence or absence of a chamfer - on the radiated power in the duct. Simulations are made on the associated diaphragm models to calculate the radiated acoustic power and compare calculation and measurment results.We show that simulation results are in accordance with experimental results.
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Sébastien Gonzalez. Résolution numérique de l'équation de Lighthill par éléments finis et équations intégrales pour l'estimation du bruit rayonné par des écoulements en conduite. Autre. Université de Technologie de Compiègne, 2013. Français. ⟨NNT : 2013COMP2087⟩. ⟨tel-00935471⟩

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