Traditional acoustic liners in aircraft engines often use honeycomb-based single- or multi-degree-of-freedom designs that target tonal frequencies. However, modern engines produce broadband noise, making these conventional liners less effective. Additive manufacturing now enables the design of tunable porous absorbers—such as those using triply periodic minimal surface (TPMS) and spinodoid structures—which offer improved broadband performance. Impedance eduction under grazing flow conditions is typically performed using a Grazing Flow Impedance Tube (GFIT), such as the one at NASA Langley. This method relies on the Prony Method with the Ingard-Myers boundary condition, which assumes the liner is locally reacting—that is, acoustic propagation occurs only normal to the surface. However, porous absorbers are inherently extended reacting, violating this assumption and compromising eduction accuracy. This study investigates whether internal partitions can be used to suppress lateral propagation in extended reaction liners, thereby promoting locally reacting behavior. By varying the partition spacing, local reaction-like behavior and tunability are observed. These results suggest that partitioning enables more accurate impedance eduction and paves the way for advanced, broadband, and tunable liner designs for next-generation aeroacoustic applications.
Hardy et al. (Wed,) studied this question.