A computational-aeroacoustics (CAA) code in the time domain has been developed for duct acoustics problems. A time-domain broadband impedance boundary condition is implemented in the code to simulate the acoustic liner. To verify the boundary condition in a duct environment, the CAA code is used to solve a semi-infinite two-dimensional duct problem with an acoustic liner for cases both with and without a sheared mean flow. The results from the numerical prediction tool agree excellently with the analytic solutions. In addition, the CAA code is validated by the experimental data from the NASA Langley Research Center flow impedance tube facility. It predicts accurately both the amplitude and the phase of the sound propagation from the NASA experiment. In both the verification and the validation problems, the no-slip condition is assumed for the mean flow to avoid the controversy over the condition of particle displacement continuity and the condition of particle velocity continuity and also to ensure the well-posedness of a time-domain broadband impedance boundary condition.
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