GLTRS--Glenn
TITLE AND SUBTITLE:
Cavity Resonance Suppression Using Miniature Fluidic Oscillators

AUTHOR(S):
Ganesh Raman, Surya Raghu, and Timothy J. Bencic

REPORT DATE:
April 1999

FUNDING NUMBERS:
WU-522-31-23-00

PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
John H. Glenn Research Center at Lewis Field
Cleveland, Ohio 44135-3191

PERFORMING ORGANIZATION REPORT NUMBER:
E-11635

SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Washington, DC 20546-0001

REPORT TYPE AND DATES COVERED:
Technical Memorandum

SPONSORING/MONITORING AGENCY REPORT NUMBER:
NASA TM-1999-209074
AIAA-99-1900

SUPPLEMENTARY NOTES:
Prepared for the 5th Aeroacoustics Conference sponsored by the American Institute of Aeronautics and Astronautics and the Confederation of European Aerospace Societies, Seattle, Washington, May 10-12, 1999. Copyright © 1999 by G. Raman and S. Raghu, Published by the American Institute of Aeronautics and Astronautics, Inc. with persmission. Ganesh Raman, Dynacs Engineering Co., Inc., 2001 Aerospace Parkway, Brook Park, Ohio 44142 (work funded by NASA Contract NAS3-98008); Surya Raghu, Bowles Fluidics Corporation, Columbia, Maryland; Timothy J. Bencic, NASA Glenn Research Center. Responsible person, Ganesh Raman, organization code 5940, (216) 977-1102.

ABSTRACT:
We present a novel approach to suppressing jet-cavity interaction tones using miniature fluidic devices. We first characterize miniature fluidic oscillators and then assess their effectiveness for cavity tone suppression. Further, we evaluate mass flow requirements for effective unsteady fluid mass addition. The fluidic devices used had no moving parts and could provide oscillatory flow of prescribed waveforms (sine, square, and saw-toothed) at frequencies up to 3 KHz. Our testbed for a detailed evaluation of the fluidic excitation (square wave) technique was the flow-induced resonance produced by a jet flowing over a cavity with an (length/depth) ratio of 6. In addition to schlieren photography and acoustic measurements we used photoluminescent Pressure Sensitive Paint (PSP) to map pressures on the cavity's floor for the unperturbed and fluidically excited cases. When located at the upstream end of the cavity floor, the miniature fluidic device was successful in suppressing cavity tones by as much as 10 dB with mass injection rates of the order of only 0.12% of the main jet flow. Similar mass flow rates of oscillatory flow near the downstream end of the cavity floor had no effect on the resonant cavity tones. Additionally, steady upstream mass flow addition at the same levels as those for fluidic excitation affected cavity tones only marginally (1 dB reduction). Furthermore, acoustic excitation at the same frequency as that produced by the fluidic device or its harmonic at comparable amplitudes did not affect the cavity resonance. Our results provide not only an example of the effectiveness of fluidic excitation but offer grounds for believing that vast possibilities exist for its use in aeroacoustic control.

SUBJECT TERMS:
Jets; Cavities; Resonance; Screech

NUMBER OF PAGES:
31

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