Time-domain simulation of acoustic propagation in a lined duct

An inviscid, spatial time-domain numerical simulation is employed to comput e acoustic wave propagation in a duct treated with an acoustic liner. The m otivation is to assess the effects on sound attenuation of bias flow passed through the liner for application to noise suppression in jet engine nacel les. Physically, the liner is composed of porous sheets with backing air ca vities. The mathematical model lumps the sheets' presence into a continuous empirical source term which modifies the right-hand side of the momentum e quations. This source term specifies the time-domain characteristics of the frequency-domain resistance and reactance of the liner's component sheets. Nonlinear behavior of the liner sheets at high sound pressure levels is in cluded in the form of the source term. The source term constants are empiri cally matched to frequency-domain impedance data via a one-dimensional nume rical impedance tube simulation. The resulting liner model is then incorpor ated into a two-dimensional Euler solver and used for simulations of a real istic duct configuration. Sound pressure levels and axially transmitted pow er are computed to assess the attenuation effects of various magnitudes of bias flow. Simulation results are compared to available experimental data f rom a geometrically similar lined duct. (C) 2001 Published by Elsevier Scie nce Ltd.