Acoustic impedance of orifices with grazing flow

Diana Bejsenbaeva,Alexandr Komkin,Mikhail Mironov,Valeriy Moskalenko,A.I Komkin,A.I Bykov

doi:10.1051/matecconf/202032000015

Diana Bejsenbaeva, Alexandr Komkin + Show 4 more

Open Access

https://doi.org/10.1051/matecconf/202032000015

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Abstract

The paper presents an overview of the results of studies of acoustic impedance of orifices with grazing airflow. Empirical models of orifice impedance, which take into account the grazing flow, and the existing methods of measuring the acoustic impedance of orifices and the experimental setup created for this purpose are analyzed. A simpler way of measuring the acoustic characteristics of an orifice with grazing flow is considered. The scheme of the developed measuring installation and its general appearance are given.

Highlights

Perforated elements are widely used in mufflers for intake and exhaust systems of engines [13]
As a rule, perforated elements are exposed to grazing flow, and it is known that this flow can significantly affect the acoustic impedance of orifices in the perforated elements
The acoustic resistance of perforated elements as the ratio of the pressure difference between the front and backside of the perforated elements to the particle velocity inside the perforated elements in the form where Z is the acoustic impedance, pf is the sound pressure from the front side of the perforation, pr is the sound pressure from the backside of the perforation and u' is the average particle velocity in the orifice of the perforation

Summary

Introduction

Perforated elements are widely used in mufflers for intake and exhaust systems of engines [13]. It should be noted that in this case, strict mathematical modeling of the mechanisms that determine acoustic impedance is significantly more complicated. For this reason, most of the existing impedance models are empirical and, besides, most of them are only for the conditions of the grazing average flow. The aim of this work is to review the experimental studies carried out in this direction It consists in the analysis of measurement techniques, comparative evaluation of measurement results taking into account the approximation of the results obtained by analytical expressions, as well as the development of an improved approach to measurements of the acoustic impedance of orifices

Measurement of orifices acoustic impedance on the sidewall of the duct

Empirical formulas for acoustic impedance of orifices

Experiment setup

Conclusion