Development of a Grazing Flow Rig for Comprehensive Acoustic Liner Characterisation and Advanced Manufacturing
In collaboration with University of Southampton, Boeing Global Technology – Europe
Erika Quaranta, Bruce Kakimpa, Abdullah Azam, Lucas Jiranek, David M. Milliken, Chaitanya Paruchuri
This paper presents the development of a multimodal grazing‑flow rig at the University of Southampton for comprehensive acoustic liner characterisation under realistic flow conditions. The rectangular duct geometry supports higher‑order mode propagation and detailed spatial pressure measurements, enabling assessment of liner performance beyond traditional plane‑wave impedance approaches. High‑fidelity CFD simulations are employed to predict liner impedance from unit‑cell analyses, which are subsequently applied as boundary conditions in FEM simulations to reconstruct the duct‑scale acoustic field. FEM results demonstrate significant modal scattering above cut‑off, even under nominal plane‑wave excitation, highlighting the importance of multimodal analysis for realistic liner assessment. Experimental measurements conducted on a conventional single‑degree‑of‑freedom liner confirm strong flow‑dependent behaviour, with increased grazing flow reducing apparent liner effectiveness. Increased source level is observed to influence liner performance primarily at the highest tested Mach number, leading to an increase in peak insertion loss. The combined CFD–FEM–experimental framework aims to establish a robust UK‑based capability for full‑spectrum industrial liner development and to provide a validation pathway for advanced liner concepts enabled by additive manufacturing.