Coupled Matryoshka liner for broadband sound absorption under grazing flow

Abstract

The development of high-performance acoustic liners for grazing flow environments remains a significant challenge due to acoustic performance degradation caused by aerodynamically induced impedance mismatch from sound–vortex interactions. In this work, we propose a coupled Matryoshka acoustic liner (CMAL) that can maintain broadband sound attenuation with high absorption peaks and dips across static and grazing flow conditions. The CMAL consists of inserted micro-perforated panels (MPPs) and nested cavities. The Matryoshka-type nested cavities create multiple resonances at subwavelength scales, while the interior MPPs enhance mutual coupling among the cavities. This configuration achieves broad absorption bandwidth and high absorption peaks and dips. On this basis, a theoretical model incorporating flow-induced impedance is developed, and a computational fluid dynamics approach is employed to successfully predict the broadband acoustic performance of the proposed CMAL, including high absorption peaks and dips, even at high flow speeds of 30 m/s. Finally. experimental results validated both the theoretical and numerical models, confirming the overall performance of the CMAL. The optimized design effectively maintains or even enhances transmission loss (TL) peaks and troughs under grazing flow. Specifically, the liner achieves an average TL of 18.18 dB across the 200–1700 Hz range at 30 m/s, with only a 3.9 % reduction compared to static conditions. This robust performance demonstrates the CMAL's exceptional adaptability to grazing flow environments.