Experimental investigation of Over-Tip-Rotor circumferential groove liners has shown potential for fan noise suppression in turbofan engines whilst providing minimal penalty in fan aerodynamic performance. The validation of Over-Tip-Rotor liner analytical prediction models against published experimental data requires the modelling of an equivalent impedance for such acoustic treatments. This paper describes the formulation of two analytical groove impedance models as semi-locally reacting liners, that is locally reacting in the axial direction and non-locally reacting in the azimuthal direction. The models are cross-verified by comparison with high-order FEM simulations, and applied to a simplified Over-Tip-Rotor configuration consisting of multiple grooves excited by a monopole point source located close to the grooved surface.

中文翻译：

---

用于抑制过尖转子风扇噪声的经过声学处理的圆周凹槽的阻抗建模

Over-Tip-Rotor 圆周凹槽衬垫的实验研究表明，它具有抑制涡轮风扇发动机风扇噪声的潜力，同时对风扇空气动力学性能的影响最小。根据已发布的实验数据验证 Over-Tip-Rotor 衬垫分析预测模型需要对此类声学处理的等效阻抗进行建模。本文将两个分析槽阻抗模型的公式描述为半局部反应衬里，即在轴向上局部反应和在方位角方向上非局部反应。这些模型通过与高阶 FEM 模拟的比较进行交叉验证，并应用于简化的 Over-Tip-Rotor 配置，该配置由位于靠近凹槽表面的单极点源激发的多个凹槽组成。