The design of acoustic liners with complex cavities for a wide frequency range of attenuation using numerical method is investigated in this paper. Three novel liner concepts are presented, demonstrating predicted improvements in broadband sound absorption when compared with that for conventional designs. The liners include a slanted septum core, a slanted septum core with varying percentage open area, and a MultiFOCAL concept. A finite element model of a normal incidence impedance tube is developed using COMSOL Multiphysics modeling software to predict the acoustic properties (resistance and reactance) of liners at medium and high sound pressure levels, and to study the impact of variations in the liner design parameters. The impedance tube finite element model incorporates non-linear semi-empirical impedance equations, validated by comparing numerical results with measurements performed on a single-degree-of-freedom liner, with a perforated face sheet, at high sound pressure level. The design variables of the novel liner concepts are optimized using a hybrid automated optimisation procedure. The low-frequency optimum slanted septum core concept with an open area of 4.5% for the face sheet and 18% for the short slanted septum is predicted to have an absorption level of at least 14 dB in the frequency range of 400–1000 Hz for normally incident pure tone excitations at 150 dB. The slanted septum core concept with varying percentage open area, with broadband optimum design variables, is predicted to have good broadband sound absorption levels of at least 10 dB in the frequency range of 570–3800 Hz. Finally, the MultiFOCAL liner concept with optimised percentage open areas is predicted to have an excellent broadband sound absorption levels of at least 14 dB, for pure tone excitations at 150 dB, in the frequency range of 900–5300 Hz. This work will be followed by optimisation of the face sheet geometries of these novel liner designs in order to maximise lined duct attenuation for aircraft engine applications.

本文研究了使用数值方法设计具有广泛衰减频率范围的复杂腔体声学衬垫。提出了三个新颖的衬垫概念，展示了与传统设计相比，宽带吸声的预测改进。衬垫包括一个倾斜的隔膜芯、一个具有不同百分比开放面积的倾斜隔膜芯和一个 MultiFOCAL 概念。使用 COMSOL Multiphysics 建模软件开发了一个法向入射阻抗管的有限元模型，以预测中高声压级下衬管的声学特性（电阻和电抗），并研究衬管设计参数变化的影响。阻抗管有限元模型包含非线性半经验阻抗方程，通过将数值结果与在高声压级下在带有穿孔面板的单自由度衬垫上进行的测量进行比较来验证。使用混合自动优化程序优化新型衬管概念的设计变量。低频最佳倾斜隔膜芯概念，面板的开放面积为 4.5%，短倾斜隔膜的开放面积为 18%，预计在 400-1000 Hz 的频率范围内，吸收水平至少为 14 dB。 150 dB 的正常入射纯音激发。具有不同开口面积百分比的倾斜隔膜核心概念，具有宽带优化设计变量，预计在 570-3800 Hz 的频率范围内具有至少 10 dB 的良好宽带吸声水平。最后，具有优化百分比开放区域的 MultiFOCAL 衬垫概念预计具有至少 14 dB 的出色宽带吸声水平，对于 150 dB 的纯音激发，在 900-5300 Hz 的频率范围内。这项工作之后将优化这些新型衬里设计的面板几何形状，以最大化飞机发动机应用的衬里管道衰减。