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Communication Dans Un Congrès Année : 2020

Influence of flow on trapped modes in ducts

Résumé

It is known that an obstacle placed in an acoustic waveguide can result in a trapped mode around this obstacle. The presence of this trapped mode can be observed on the amplitudes of the transmission and reflection coefficients through a Fano-like resonance. The frequency and the quality factor of this resonance depend both on the size of the obstacle and on its distance to the axis of the guide. Here, a rigid cylinder is placed inside an acoustic waveguide and we study the influence of an imposed flow around the cylinder. The flow is exponentially decaying away from the cylinder, such that the fluid is at rest far from it. We show that the trapped mode still exists in the presence of flow, and that it can be excited even when the cylinder is placed on the axis of the guide. Moreover, the problem becomes asymmetric in the presence of flow. Indeed, even though the amplitudes of the scattering coefficients remain the same regarding the direction of the incident wave, the phase of the reflection coefficient vary whereas the incident wave comes from the left or from the right. This phase difference appears to be happening only around the frequency of the trapped mode. This problem is studied both in a full finite elements model and in a simplified multi-modal one.
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Dates et versions

hal-03229444 , version 1 (19-05-2021)

Identifiants

Citer

Charlotte Saverna, Vincent Pagneux, Yves Aurégan, Gwenael Gabard. Influence of flow on trapped modes in ducts. Forum Acusticum, Dec 2020, Lyon, France. pp.779-779, ⟨10.48465/fa.2020.1029⟩. ⟨hal-03229444⟩
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