4. Validation of the propagation methodology
The application of the WEM with a flow impedance boundary condition to acoustic liner problems is validated by comparing results obtained using this methodology with experimental data from the grazing incidence tube (GIT) at the NASA Langley Research Center. This data, presented by Jones et al. in Ref. [11],was collected specifically for the purpose of validating acoustic propagation codes and is the most comprehensive available. As such, it has been widely used to benchmark the use of flow impedance boundary conditions in numerical schemes [12,26,14,13].