Duct Liner Optimization for Turbomachinery Noise Sources

An acoustical field theory for axisymmetric, multisectioned lined ducts with uniform flow profiles is combined with a numerical minimization algorithm to predict optimal liner configurations having one, two, and three sections. Source models studied include a point source located on the axis of the duct and rotor/outlet-stator viscous wake interaction effects for a typical research compressor operating at an axial flow Mach number of about 0.4. For this latter source, optimal liners for equipartition-of-energy, zero-phase, and least-attenuated-mode source variations are also calculated and compared with exact results. It is found that the potential benefits of liner segmentation for the attenuation of turbomachinery noise is greater than would be predicted from point source results. Furthermore, effective liner design requires precise knowledge of the circumferential and radial modal distributions. Duct acoustics, Aircraft noise, Turbomachinery noise. Presented at the 90th Meeting of the Acoustical Society of America, San Francisco, CA, 4-7 Nov 1975.