LDV-based impedance eduction technique for acoustic liners in the presence of flow
type: Dataset
description: While aircraft noise constraints become increasingly stringent, efficient duct treatment of turbofan engines requires an accurate knowledge of liner impedance with grazing flow at high acoustic levels. This thesis aims at developing an impedance eduction method in the presence of grazing flow. The inverse process is based on acoustic velocity fields acquired by Laser Doppler Velocimetry (LDV) above the liner. The liner acoustic impedance is obtained by minimization of the distance between the measured acoustic velocity field and the simulated one. Computations rely on the resolution of the 2D linearized Euler equations in the harmonic domain, spatially discretized by a discontinuous Galerkin scheme. The gradient of the objective function is achieved by the resolution, at each iteration on the liner impedance, of the direct and adjoint equations. The solver is first validated on academic test cases, then on experimental results of acoustic pressure measurements at the rigid wall opposite the liner. Secondly the method is applied to acoustic velocity measurements obtained by LDV above the liner without flow, in the ONERA B2A test bench. The last step consists in taking into account the effects of a sheared grazing flow. The impedances educed from LDV measurements in the presence of flow namely allowed to gain insight into the absorption phenomena occuring in the B2A test bench.
issued: 2026-05-14T13:30:26.271243
language: fr
modified: 2026-05-14T13:30:26.271248
contact point: Organization
  fn: CCSD
keyword: acoustic-impedance
keyword: acoustic-velocity
keyword: adjoint-equations
keyword: discontinuous-galerkin
keyword: eduction
keyword: equations-adjointes
keyword: galerkin-discontinu
keyword: impedance-acoustique
keyword: infoeu-reposemanticsdoctoralthesis
keyword: laser-doppler-velocimetry
keyword: liner
keyword: methode-inverse
keyword: physmecaacouphysics-physicsmechanics-physicsacoustics-physicsclass-ph
keyword: spiacouengineering-sciences-physicsacoustics-physicsclass-ph
keyword: theses
keyword: velocimetrie-laser-doppler
keyword: vitesse-acoustique
landing page: https://theses.hal.science/tel-00787256

LDV-based impedance eduction technique for acoustic liners in the presence of flow
type: Distribution
format: HTML
issued: 2026-05-14T13:30:26.318907
modified: 2026-05-14T13:30:26.231973
access URL: https://theses.hal.science/tel-00787256

test_moissonnage_selune
type: Agent