Jet noise suppression using flexible filaments-review

E. J. Gutmark, B. Callender, B. A. Anderson, T. R.S. Bhat, I. J. Wygnanski

Research output: Contribution to conferencePaperpeer-review


This paper describes the flow structure modifications and reduction in acoustic emissions affected by suspending flexible filaments within the center of supersonic and subsonic jets. Experiments performed with cold subsonic and underexpanded supersonic jets show that the filaments change the flow structure of the jet and may extract energy from the flow, converting the flow energy into filament vibrational / mechanical energy. Changes to the flow structure induced by the filament include weakening of the shock structure in the supersonic jet, and reduction in the mean velocity and turbulence intensity in the subsonic jet. The changes to the jet structure enable a decrease in the noise generation of the jet. Shock related and turbulent mixing noise was reduced up to 35dB for the supersonic jet, and low to mid frequency noise was reduced up to 3dB for the subsonic jet. For the subsonic jet, the filament increased the high frequency noise radiation by 2.5dB. In the underexpanded jet, the filament was determined to be most effective for any thickness greater than approximately 4% of the nozzle diameter and for lengths greater than three nozzle diameters. Temperature effects on the filament indicated that up to a temperature ratio of 1.82, which was the highest temperature ratio tested, the filament effectiveness increases with temperature.

Original languageEnglish
StatePublished - 2001
Externally publishedYes
Event39th Aerospace Sciences Meeting and Exhibit 2001 - Reno, NV, United States
Duration: 8 Jan 200111 Jan 2001


Conference39th Aerospace Sciences Meeting and Exhibit 2001
Country/TerritoryUnited States
CityReno, NV


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