Numerical simulation of multi-modal reflection in large acoustic waveguides with different terminations
Résumé
Using microphone pairs is a standard method to measure the acoustic properties of a waveguide such as the reflection coefficient at the outlet. This method is used in many experimental works before and discussed in many scientific papers. In this study, the measurement of the reflection coefficient with microphone pairs method is simulated using a numerical model that represent exactly the experimental protocol in order toprovide numerical results and support some experimental measurements.The plane mode reflection in waveguides is largely described in literature, and manytheoretical models are developed in this particular case which could be used to validate theexperimental results, however the multi-modal reflection coefficient is more difficult to derive theoretically. Therefore, this study aims to provide a basis of comparison for the experimental measurements especially for the Multi-modal reflection coefficient of higher modes. The simulations are covering open-end pipes with three different termination geometries: a pipe ended with an infinite baffle, a pipe ended with a finite flange and a pipe ended with sharp edge (unbaffled).The simulations are performed through the four major steps of a standard simulation: Pre-processing, sensitivity calculations and benchmark tests, computation and finally post-processing. In the end the numerical results are compared to experimental measurements conducted by Zhiping QIU (http://theses.univ-poitiers.fr/notice/view/59508) during his PhD study
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