Technique for evaluating the acoustic properties of a liner at grazing incidence of wave based on numerical simulation

Abstract

The paper considers a method for determining the impedance of acoustic liner sample based on numerical simulation of physical processes in resonators at a grazing incidence of a sound wave. The test section of a grazing incidence impedance tube (GIIT) and a model of acoustic liner sample, consisting of 7 honeycomb cells with a depth of 27 mm and 11.9% porous perforate facesheet is simulated. Numerical simulation is based on direct solution of the non-stationary compressible Navier-Stokes equations in a three-dimensional formulation. The pressure-time signals recorded in numerical simulation are processed by the Dean method. The obtained impedance is compared with that educed on full-scale experiment data for a single-layer acoustic liner sample, consisting of 72 honeycomb cells of a similar design. The impedance eduction is performed by minimizing the residual functional, which is the total discrepancy between the calculated and experimental acoustic pressure on the wall of the GIIT. The calculated values of the acoustic pressure are determined by the numerical solution of the Helmholtz equation and the linearized Euler equations for a duct with an impedance wall.