Verification Framework for Acoustic Mode Predictions in Ducted Swirling Flows

As aviation noise regulations become more stringent, reducing aircraft engine noise during aircraft takeoff and landing remains a critical challenge. Acoustic liners are often installed on the walls of engine inlet and exhaust ducts to attenuate the amplitude of acoustic modes propagating from the bypass fan. Improved acoustic mode predictions for ducted swirling flows are needed to optimize acoustic liners that may be placed between the rotor and stator. This paper describes the verification of the ‘Swirl’ code, a frequency-domain solver for the Linearized Euler Equations used to predict acoustic modes in ducts with swirling mean flows. The accuracy and order of accuracy of the Swirl code were verified using the Method of Manufactured Solutions (MMS) and the Method of Exact Solutions (MES). The investigation examined the numerical integration routines, the spatial differencing routines, and first cut-on axial wavenumber (eigenvalue) and radial pressure mode (eigenvector) for a uniform flow in a hard wall annular duct. Results underscore the importance of code verification in computational aeroacoustic simulations.