Acoustic Treatment Design Scaling Methods. Volume 1; Overview, Results, and Recommendations
Acoustic Treatment Design Scaling Methods. Volume 1; Overview, Results, and Recommendations

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-06-15

Total Pages: 40

ISBN-13: 9781721182558

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Scale model fan rigs that simulate new generation ultra-high-bypass engines at about 1/5-scale are achieving increased importance as development vehicles for the design of low-noise aircraft engines. Testing at small scale allows the tests to be performed in existing anechoic wind tunnels, which provides an accurate simulation of the important effects of aircraft forward motion on the noise generation. The ability to design, build, and test miniaturized acoustic treatment panels on scale model fan rigs representative of the fullscale engine provides not only a cost-savings, but an opportunity to optimize the treatment by allowing tests of different designs. The primary objective of this study was to develop methods that will allow scale model fan rigs to be successfully used as acoustic treatment design tools. The study focuses on finding methods to extend the upper limit of the frequency range of impedance prediction models and acoustic impedance measurement methods for subscale treatment liner designs, and confirm the predictions by correlation with measured data. This phase of the program had as a goal doubling the upper limit of impedance measurement from 6 kHz to 12 kHz. The program utilizes combined analytical and experimental methods to achieve the objectives. Kraft, R. E. and Yu, J. Glenn Research Center; Langley Research Center NASA/CR-1999-209120/VOL1, NAS 1.26:209120/VOL1

Acoustic Treatment Design Scaling Methods. Volume 2; Advanced Treatment Impedance Models for High Frequency Ranges
Acoustic Treatment Design Scaling Methods. Volume 2; Advanced Treatment Impedance Models for High Frequency Ranges

Author: National Aeronautics and Space Adm Nasa

Publisher: Independently Published

Published: 2018-09-22

Total Pages: 100

ISBN-13: 9781723940033

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The primary purpose of this study is to develop improved models for the acoustic impedance of treatment panels at high frequencies, for application to subscale treatment designs. Effects that cause significant deviation of the impedance from simple geometric scaling are examined in detail, an improved high-frequency impedance model is developed, and the improved model is correlated with high-frequency impedance measurements. Only single-degree-of-freedom honeycomb sandwich resonator panels with either perforated sheet or "linear" wiremesh faceplates are considered. The objective is to understand those effects that cause the simple single-degree-of- freedom resonator panels to deviate at the higher-scaled frequency from the impedance that would be obtained at the corresponding full-scale frequency. This will allow the subscale panel to be designed to achieve a specified impedance spectrum over at least a limited range of frequencies. An advanced impedance prediction model has been developed that accounts for some of the known effects at high frequency that have previously been ignored as a small source of error for full-scale frequency ranges.Kraft, R. E. and Yu, J. and Kwan, H. W.Langley Research CenterACOUSTIC IMPEDANCE; HIGH FREQUENCIES; AIRCRAFT MODELS; SCALE MODELS; AIRCRAFT NOISE; NOISE PREDICTION (AIRCRAFT); AEROACOUSTICS; HONEYCOMB STRUCTURES; PANELS; SANDWICH STRUCTURES; FAN BLADES