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Acoustic Treatment Design Scaling Methods
Acoustic Treatment Design Scaling Methods... NASA
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
DOWNLOAD EBOOK →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
Acoustic Treatment Design Scaling Methods. Volume 1; Overview, Results, and Recommendations
Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
Published: 2018-09-25
Total Pages: 42
ISBN-13: 9781724024503
DOWNLOAD EBOOK →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 5; Analytical and Experimental Data Correlation
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Published: 2018-08-27
Total Pages: 80
ISBN-13: 9781726170918
DOWNLOAD EBOOK →The primary purpose of the study presented in this volume is to present the results and data analysis of in-duct transmission loss measurements. Transmission loss testing was performed on full-scale, 1/2-scale, and 115-scale treatment panel samples. The objective of the study was to compare predicted and measured transmission loss for full-scale and subscale panels in an attempt to evaluate the variations in suppression between full- and subscale panels which were ostensibly of equivalent design. Generally, the results indicated an unsatisfactory agreement between measurement and prediction, even for full-scale. This was attributable to difficulties encountered in obtaining sufficiently accurate test results, even with extraordinary care in calibrating the instrumentation and performing the test. Test difficulties precluded the ability to make measurements at frequencies high enough to be representative of subscale liners. It is concluded that transmission loss measurements without ducts and data acquisition facilities specifically designed to operate with the precision and complexity required for high subscale frequency ranges are inadequate for evaluation of subscale treatment effects.Chien, W. E. and Kraft, R. E. and Syed, A. A.Glenn Research Center; Langley Research CenterAIRCRAFT NOISE; ACOUSTICS; FREQUENCY RANGES; DUCTS; NOISE REDUCTION; TRANSMISSION LOSS; CALIBRATING; DATA ACQUISITION; PANELS...
Acoustic Treatment Design Scaling Methods
Acoustic Treatment Design Scaling Methods: Phase Ii Final Report ... Nasa
Author: United States. National Aeronautics and Space Administration
Publisher:
Published: 2003*
Total Pages:
ISBN-13:
DOWNLOAD EBOOK →Acoustic Treatment Design Scaling Methods. Volume 4; Numerical Simulation of the Nonlinear Acoustic Impedance of a Perforated Plate Single-Degree-Of-Freedom Resonator Using a Time-Domain Finite Difference Method
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Published: 2018-08-27
Total Pages: 50
ISBN-13: 9781726170833
DOWNLOAD EBOOK →Single-degree-of-freedom resonators consisting of honeycomb cells covered by perforated facesheets are widely used as acoustic noise suppression liners in aircraft engine ducts. The acoustic resistance and mass reactance of such liners are known to vary with the intensity of the sound incident upon the panel. Since the pressure drop across a perforated liner facesheet increases quadratically with the flow velocity through the facesheet, this is known as the nonlinear resistance effect. In the past, two different empirical frequency domain models have been used to predict the Sound Pressure Level effect of the incident wave on the perforated liner impedance, one that uses the incident particle velocity in isolated narrowbands, and one that models the particle velocity as the overall velocity. In the absence of grazing flow, neither frequency domain model is entirely accurate in predicting the nonlinear effect that is measured for typical perforated sheets. The time domain model is developed in an attempt to understand and improve the model for the effect of spectral shape and amplitude of multi-frequency incident sound pressure on the liner impedance. A computer code for the time-domain finite difference model is developed and predictions using the models are compared to current frequency-domain models.Kraft, R. E.Glenn Research Center; Langley Research CenterDEGREES OF FREEDOM; NOISE REDUCTION; PRESSURE EFFECTS; SOUND INTENSITY; HONEYCOMB STRUCTURES; AIRCRAFT ENGINES; GRAZING FLOW; NOISE (SOUND); FLOW VELOCITY; MATHEMATICAL MODELS; RESONATORS; SOUND PRESSURE; NONLINEARITY...
Acoustic Treatment Design Scaling Methods. Volume 3; Test Plans, Hardware, Results, and Evaluation
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Published: 2018-08-27
Total Pages: 80
ISBN-13: 9781726170543
DOWNLOAD EBOOK →The ability to design, build, and test miniaturized acoustic treatment panels on scale-model fan rigs representative of the full-scale engine provides not only a cost-savings, but an opportunity to optimize the treatment by allowing tests of different designs. To be able to use scale model treatment as a full-scale design tool, it is necessary that the designer be able to reliably translate the scale model design and performance to an equivalent full-scale design. The primary objective of the study presented in this volume of the final report was to conduct laboratory tests to evaluate liner acoustic properties and validate advanced treatment impedance models. These laboratory tests include DC flow resistance measurements, normal incidence impedance measurements, DC flow and impedance measurements in the presence of grazing flow, and in-duct liner attenuation as well as modal measurements. Test panels were fabricated at three different scale factors (i.e., full-scale, half-scale, and one-fifth scale) to support laboratory acoustic testing. The panel configurations include single-degree-of-freedom (SDOF) perforated sandwich panels, SDOF linear (wire mesh) liners, and double-degree-of-freedom (DDOF) linear acoustic panels.Yu, J. and Kwan, H. W. and Echternach, D. K. and Kraft, R. E. and Syed, A. A.Langley Research CenterAIRCRAFT NOISE; ACOUSTIC PROPERTIES; SCALE MODELS; COST REDUCTION; FLOW RESISTANCE; GRAZING FLOW; IMPEDANCE MEASUREMENT; WIRE CLOTH; SANDWICH STRUCTURES; MINIATURIZATION; DEGREES OF FREEDOM; DUCTS...
