Interest in the characterization of the aerodynamic drag performance of acoustic liners has increased in the past several years. This paper details experiments in NASA Langley's Grazing Flow Impedance Tube to quantify the relative drag of several conventional perforate-over-honeycomb liner configurations. For a fixed porosity, facesheet hole diameter and cavity depth are varied to study the effect of each. These configurations are selected to span the range of conventional liner geometries used in commercial aircraft engines. Detailed static pressure and acoustic measurements are made for grazing flows up to M=0.5 at 140 dB SPL for tones between 400 and 2800 Hz. These measurements are used to calculate a resistance factor (λ) for each configuration. Analysis shows a correlation between perforate hole size and the resistance factor but cavity depth seems to have little influence. Acoustic effects on liner drag are observed to be limited to the lower Mach numbers included in this investigation.
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机译：在过去的几年中，人们越来越关注声学衬里的气动阻力性能。本文详细介绍了在NASA Langley的“掠流阻力管”中进行的实验，以量化几种传统的孔眼蜂窝结构的相对阻力。对于固定的孔隙率，面板孔直径和型腔深度会有所不同，以研究每种效果。选择这些构型以跨越在商用飞机发动机中使用的常规衬套几何形状的范围。对于在400和2800 Hz之间的音调，在140 dB SPL时高达M = 0.5的放牧流进行了详细的静压和声学测量。这些测量用于计算每种配置的电阻系数（λ）。分析表明，孔眼尺寸与阻力系数之间存在相关性，但型腔深度似乎影响不大。观察到的对衬管阻力的声学影响仅限于此研究中包括的较低马赫数。
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