Small Business Innovation Research/Small Business Tech Transfer
Validation of Standing Wave Liner Impedance Measurement Method
Project Description
Hersh Acoustical Engineering, Inc. proposes to establish the feasibility and practicality of using the Standing Wave Method (SWM) to measure the impedance of perforate-over-honeycomb liners exposed to both grazing and orifice bias flow. By measuring liner generated reflected sound in a duct, the SWM calculates the impedance of one or more rows of resonator liners, providing the liner axial length is small relative to the wavelengths of the incident sound and the sound frequencies are sufficiently low that the effects of acoustic refraction by mean flow velocity gradients are negligible. Work Plan. Tasks are separated into test preparation, test execution, and analysis and reporting. Tests will be conducted in the University of Cincinnati Grazing Flow Test Facility and most preparation work will be focused on modifying the facility to permit the enabling of bias flow in the facility. The facility design will be such to enable measurements of resonator impedance without grazing flow, with grazing flow and with grazing and bias flow. The following tasks are proposed. Task 1, Design of test resonator, Task 2, Quote, manufacture, and installation of test resonators, Task 3, Modification of test setup and data processing codes, Task 4, Impedance measurements with no grazing or bias flow, Task 5, Impedance measurement with grazing flow and no bias flow, Task 6,Impedance measurement with grazing flow and bias flow, Task 7, Measurement of resonator impedance in the UC acoustic wave tube, and Task 8, Final Report.
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Anticipated Benefits
The Standing Wave Method of measuring resonator liner impedance method offers the potential to (1) replace the current Dean Two-Microphone liner impedance method, (2) assess the importance of leading and trailing edge effects on resonator impedance, and hence design and performance, in the presence of steady-state grazing flow and (3) complement the single mode, grazing flow impedance eduction research conducted by Watson, et.al, presented at the June, 2014 AIAA Aeroacoustics conference held in Atlanta, GA and (4) improve the acoustic performance of manufacturers of aircraft nacelles and HVAC ducts. Finally, if successful, the SWM could also be used to conduct extensive resonator liner impedance measurements of the effects of grazing and orifice bias flow on both tonal and broadband sound in a follow-on Phase 2 research program (if awarded), the importance of which was noted in Section A1.02 of the RFP.
Assuming the Standing Wave Method of the measurement of resonator liner impedance in the presence of grazing flow has been validated, it offers the potential to improve flow duct resonator design and sound absorption performance. The software and hardware technology developed under the Phase I program could also be used to assist commercial and military manufactures of (1) aircraft nacelle manufacturers, (2) HVAC duct noise suppressors, (3) space heaters and (4) air conditioner manufactures in the development of efficient sound absorbing resonator liners. In addition, the University of Cincinnati intends to provide to the aircraft and duct acoustics commercial communities, the use of its Standing Wave Test Facility to measure the effect of grazing flow and bias flow on the impedance of potential commercial sound absorbing liners. More »
Assuming the Standing Wave Method of the measurement of resonator liner impedance in the presence of grazing flow has been validated, it offers the potential to improve flow duct resonator design and sound absorption performance. The software and hardware technology developed under the Phase I program could also be used to assist commercial and military manufactures of (1) aircraft nacelle manufacturers, (2) HVAC duct noise suppressors, (3) space heaters and (4) air conditioner manufactures in the development of efficient sound absorbing resonator liners. In addition, the University of Cincinnati intends to provide to the aircraft and duct acoustics commercial communities, the use of its Standing Wave Test Facility to measure the effect of grazing flow and bias flow on the impedance of potential commercial sound absorbing liners. More »
Project Library
Primary U.S. Work Locations and Key Partners
| Organizations Performing Work | Role | Type | Location |
|---|---|---|---|
| Hersh Acoustical Engineering, Inc. | Lead Organization |
Industry
Women-Owned Small Business (WOSB)
|
Calabasas, California |
Langley Research Center
(LaRC)
|
Supporting Organization | NASA Center | Hampton, Virginia |
Primary U.S. Work Locations
-
California
-
Virginia
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