IFAR liner benchmark challenge #1 – DLR impedance eduction of uniform and axially segmented liners and comparison with NASA results. Issue 5 (September 2021)

• Record Type: Journal Article
• Authors: Bake, Friedrich; Burgmayer, Ralf; Schulz, Anita; Knobloch, Karsten; Enghardt, Lars; Jones, Michael G
• Is Part Of: International journal of aeroacoustics. Volume 20:Issue 5/7(2021)
• Page Start: 478
• Page End: 496
• Publication Date: 2021-09
• Subjects: Liner characterization -- impedance eduction -- liner test facilities -- IFAR benchmark; Aerodynamic noise -- Periodicals; Acoustical engineering -- Periodicals; Sound -- Periodicals; 629.1323
• DOI: 10.1177/1475472X211023844
• Languages: English
• ISSNs: 2048-4003

Abstract

This paper presents the contribution from the German Aerospace Center (DLR) to the first liner benchmark challenge under the framework of the International Forum for Aviation Research (IFAR). Therefore, two sets of acoustically damping wall treatments, called 'liner samples', have been produced by additive manufacturing based on the design data provided by NASA coordinating this benchmark. These liner samples have been integrated and acoustically characterized in the liner flow test facility DUCT-R at DLR Berlin as well as in the liner flow test facility GFIT at NASA Langley. Besides the dissipation coefficients and the axial pressure profiles, the liner wall impedance was educed by first determining the axial wave numbers and then applying a straightforward method based on the one-dimensional Convected Helmholtz Equation. Finally, the comparison of the liner impedance values to the NASA results show a fairly good agreement.