Impedance eduction for uniform and multizone acoustic liners

2021 ◽  
pp. 1475472X2110238
Author(s):  
Michael G Jones ◽  
Douglas M Nark ◽  
Brian M Howerton
Keyword(s):  
Impedance Spectra ◽  
International Forum ◽  
Acoustic Liners ◽  
Prony Method ◽  
Research Challenges ◽  
Test Conditions ◽  
Acoustic Liner ◽  
Flow Impedance ◽  
Grazing Flow ◽  
Computationally Expensive

This paper presents results for five uniform and two multizone liners based on data acquired in the NASA Langley Grazing Flow Impedance Tube. Two methods, Prony and CHE, are used to educe the impedance spectra for each of these liners for many test conditions. The Prony method is efficient and generally provides accurate results for uniform liners, but is not well suited for multizone liners. The CHE method supports assessment of both uniform and multizone liners, but is much more computationally expensive. The results from these liners demonstrate the efficacy of both eduction methods, but also clearly demonstrate that sufficient attenuation is required to support accurate impedance eduction. For the liners considered in this study, the data indicate approximately 3 dB attenuation is needed for each zone of a multizone liner in order to ensure quality impedance eduction results. This study was conducted in response to two acoustic liner research challenges in support of a collaboration of multiple national laboratories under the International Forum for Aviation Research.

scholarly journals Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform description

2021 ◽  
Vol 263 (6) ◽  
pp. 508-518
Author(s):  
Frank Simon ◽  
R. Roncen ◽  
P. Vuillemin ◽  
P. Klotz ◽  
Fabien Méry ◽  
...  
Keyword(s):  
Transmission Loss ◽  
Low Frequency ◽  
Total Sample ◽  
Software Platform ◽  
Linearized Euler Equations ◽  
Design And Optimization ◽  
Acoustic Liners ◽  
Acoustic Liner ◽  
Frequency Regime ◽  
Grazing Flow

In the context of aircraft noise reduction in varied applications where a cold or hot shear grazing flow is present (i.e., engine nacelle, combustion chamber, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints limit the efficiency of conventional liner technology. Therefore, liner design must take into account the dimensional and phenomenological characteristics of constituent materials, assembly specifications and industrial requirements involving multiphysical phenomena. To perform the single/multi-objective optimization of complex meta-surface liner candidates, a software platform coined OPAL (OPtimisation of Acoustic Liners) was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial elementary acoustic layers along a given duct. Then, the physical properties of this liner can be optimized, relatively to weighted objectives, for a given flow and frequency range: impedance target, maximum absorption coefficient or transmission loss with a total sample size and weight... The presentation will focus on the different elementary bricks and assembly of a problem (from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin simulations of the Linearized Euler Equations).

A review of variable-impedance acoustic liner concepts developed at NASA

2021 ◽  
Vol 263 (5) ◽  
pp. 1633-1644
Author(s):  
Michael Jones
Keyword(s):  
Prediction Models ◽  
Normal Incidence ◽  
Wide Frequency Range ◽  
Acoustic Properties ◽  
Surface Porosity ◽  
Acoustic Liner ◽  
Impedance Tubes ◽  
Flow Impedance ◽  
Grazing Flow ◽  
Langley Research Center

This paper presents results attained in the NASA Langley Research Center test rigs using concepts for which the impedance varies over the surface of the liner. These liners are typically designed for significant sound absorption over a wide frequency range, but it is also possible to tune the design to achieve increased absorption at selected frequencies. A brief review is provided regarding a number of variable-impedance concepts. The first is a modified version of a conventional two-layer liner, in which the embedded septum location and acoustic properties are different for adjacent core chambers. Two concepts employ core chambers with different lengths, one with bent chambers to allow packaging within a limited volume, and the other with shared inlet ports to reduce the surface porosity. The last employs a perforated facesheet in which the hole diameter and porosity are varied over the surface of the liner. Data acquired in the NASA normal incidence and grazing flow impedance tubes are used to demonstrate the capabilities of these concepts. Impedance prediction models are also presented for comparison with these measured data.

Proposal of Acoustic Liners Combined with Fine-Perforated-Film

2021 ◽  
Vol 263 (1) ◽  
pp. 5475-5484
Author(s):  
Yo Murata ◽  
Tatsuya Ishii ◽  
Shunji Enomoto ◽  
Hideshi Oinuma ◽  
Kenichiro Nagai ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Absorption Efficiency ◽  
Acoustic Energy ◽  
Experimental Result ◽  
Acoustic Liners ◽  
Acoustic Liner ◽  
The Face ◽  
Grazing Flow ◽  
Face Plate ◽  
Perforated Film

This paper deals with a resonant type liner panel with a special surface structure. A typical resonant type liner panel generally consists of a perforated face plate, cells, and a back rigid plate. One of the technical challenges of the acoustic liners applied to the future ultra-high bypass ratio engines is to increase the sound absorption efficiency under grazing conditions because the nacelle, covering of the engine, tends to reduce its length and the lined area. It is known that the sound absorption of the conventional liners tends to deteriorate as grazing flow increases. The authors introduced a special thin acoustically transparent film over the face plate of the acoustic liner. The film, a fine perforated film (FPF), is expected to prevent the interaction of the grazing flow with the opening of the liner face plate. An experimental result with a flow duct rig in JAXA confirmed that the proposed combination of the acoustic liner and the FPF improved the absorption in acoustic energy under grazing conditions, compared with the sole acoustic liner and simple treatment of the FPF.

Distributed Parameter Acoustic Modeling of a Perforation With Bias Flow

2011 ◽  
Author(s):  
Alireza Mazdeh ◽  
Reza Kashani
Keyword(s):  
Flow Characteristics ◽  
Distributed Parameter ◽  
Thermoacoustic Instabilities ◽  
Acoustic Liners ◽  
Current State ◽  
Large Eddy ◽  
Acoustic Liner ◽  
Bias Flow ◽  
Grazing Flow ◽  
Semi Empirical

Perforated acoustic liners (screech liners) with bias flow are commonly used for mitigation of thermoacoustic instabilities in augmentors. In addition to cooling the liner, the flow of air thru the liner perforation (dubbed ‘bias flow’) improves the damping effectiveness of the liner thru enhancing its energy dissipation. These liners are currently being designed using empirical design rules followed by build-test-improve steps, basically trial and error. The development of physics-based tools to assist in the design of such liners is of great interest to practitioners. In this paper, the existing work in developing analytical, semi-empirical, and numerical techniques such as Large-Eddy Simulations (LES) in exploring the damping effectiveness of an acoustic liner with bias flow are reviewed. The paper continues with presenting the research in progress that has been conducted by the authors in this area with the goal of expanding the numerical modeling work beyond the current state of the art by including the variables that were not incorporated in previous studies including, but not limited to, hole orientation, combined effect of tangential grazing flow and bias flow interaction with acoustics, and different flow characteristics (Mach and Reynolds number). In addition, the spatial distribution of pressure and velocity over the aperture area (instead of the current practice of averaging these variables) are being looked at.

Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform applications

2021 ◽  
Vol 263 (6) ◽  
pp. 152-163
Author(s):  
Remi Roncen ◽  
Pierre Vuillemin ◽  
Patricia Klotz ◽  
Frank Simon ◽  
Fabien Méry ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Low Frequency ◽  
Small Scale ◽  
Software Platform ◽  
Total Size ◽  
Linearized Euler Equations ◽  
Design And Optimization ◽  
Acoustic Liners ◽  
Frequency Regime ◽  
Grazing Flow

In the context of noise reduction in diverse applications where a shear grazing flow is present (i.e., engine nacelle, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints currently limit the efficiency of classic liner technology. To perform the required multi-objective optimization of complex meta-surface liner candidates, a software platform called OPAL was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial assembly of unit acoustic elements, including the recent concept of LEONAR materials. Then, the physical properties of this liner can be optimized, relatively to given weighted objectives (noise reduction, total size of the sample, weight), for a given configuration. Alternatively, properties such as the different impedances of liner unit surfaces can be optimized. To accelerate the process, different nested levels of optimization are considered, from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin resolution of the Linearized Euler Equations. The presentation will focus on the different aspects of liner design considered in OPAL, and present an application on different samples made for a small scale aeroacoustic bench.

ON DESIGNING IMPEDANCE TUBE WITH GRAZING FLOW

Akustika ◽  
2021 ◽  
pp. 80
Author(s):  
Vadim Palchikovskiy ◽  
Igor Khramtsov ◽  
Aleksander Kuznetsov ◽  
Victor Pavlogradskiy
Keyword(s):  
Numerical Simulation ◽  
Analytical Solutions ◽  
Gas Dynamics ◽  
Aircraft Engine ◽  
Design Parameters ◽  
Experimental Setup ◽  
Structural Units ◽  
Impedance Tube ◽  
Acoustic Liners ◽  
Grazing Flow

The article considers the general issues arising in designing the experimental setup “Impedance tube with grazing flow”, the main structural units of the setup, and their purpose. It is given the basic requirements to be provided by the setup when testing samples of acoustic liners used in an aircraft engine. The choosing of the design parameters of the setup is based on the analysis of the known analytical solutions of the acoustics and gas dynamics, and on the numerical simulation of the grazing flow in the impedance tube.

On Reducing Piping Vibration Levels: Attacking the Source

2002 ◽  
Author(s):  
Zheji Liu ◽  
D. Lee Hill ◽  
Roman Motriuk
Keyword(s):  
Noise Level ◽  
Frequency Noise ◽  
Computational Studies ◽  
Acoustic Liners ◽  
Blade Passing Frequency ◽  
The People ◽  
Acoustic Liner ◽  
Structural Failures ◽  
High Level ◽  
Novel Design

Centrifugal compressors used in the pipeline market generate very strong noise, which is typically dominated by the blade passing frequency and its higher harmonics. The high level noise is not only very disturbing to the people living nearby the installation site but also causes expensive structural failures in the downstream piping. A novel design of Helmholtz array has been developed to address this type of noise problem. Computational studies show that the installation of the Helmholtz array acoustic liner on the compressor diffuser walls is very effective in reducing noise level of the compressor, especially the dominant blade passing frequency noise. The acoustic liner design has been built and tested at an installation site by the customer. The data clearly shows that the use of acoustic liners is indeed very effective in the reduction of both the noise and the vibration levels of the machine.

Numerical Analysis of Acoustic Liner Performance in grazing flow

2019 ◽  
Author(s):  
Shunji Enomoto ◽  
Tatsuya Ishii ◽  
Toshio Nishizawa ◽  
Hidemi Toh
Keyword(s):  
Numerical Analysis ◽  
Acoustic Liner ◽  
Grazing Flow
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