Time-domain simulation of acoustic propagation in a lined duct

An inviscid, spatial time-domain numerical simulation is employed to compute acoustic wave propagation in a duct treated with an acoustic liner. The motivation is to assess the effects on sound attenuation of bias flow passed through the liner for application to noise suppression in jet engine nacelles. Physically, the liner is composed of porous sheets with backing air cavities. The mathematical model lumps the sheetsʹ presence into a continuous empirical source term which modifies the right-hand side of the momentum equations. This source term specifies the time-domain characteristics of the frequency-domain resistance and reactance of the linerʹs component sheets. Nonlinear behavior of the liner sheets at high sound pressure levels is included in the form of the source term. The source term constants are empirically matched to frequency-domain impedance data via a one-dimensional numerical impedance tube simulation. The resulting liner model is then incorporated into a two-dimensional Euler solver and used for simulations of a realistic duct configuration. Sound pressure levels and axially transmitted power are computed to assess the attenuation effects of various magnitudes of bias flow. Simulation results are compared to available experimental data from a geometrically similar lined duct.