On the use of a Stress-Impedance Model to describe sound propagation in a lined duct with grazing flow

TL;DR

This paper introduces a Stress-Impedance model for sound propagation in lined ducts with grazing flow, incorporating both wall impedance and tangential stress to better capture flow-wall interactions.

Contribution

It proposes a novel model combining impedance and friction factor to describe flow-wall interactions in lined ducts with grazing flow.

Findings

The model improves understanding of momentum transfer mechanisms.

It accounts for viscous and unsteady effects at the wall.

Enhances prediction accuracy of sound propagation in flow ducts.

Abstract

With flow, the acoustical effect of a lined wall cannot be described by a single quantity like the wall impedance. At least two quantities are required. In addition to the impedance, the unsteady tangential force exerted by the wall on the flow has to be taken into account. This force is due either to viscous effects or to the unsteady transfer of axial momentum from the flow into the lined wall. The paper describes a Stress--Impedance model where the two variables used are the impedance and the friction factor that links the pressure to a tangential stress at the wall. The use of a wall stress helps to better understand the mechanisms of momentum transfer between the flow and the wall in the vicinity of an acoustic treatment.