A simple technique of locating noise sources of a jet under simulated forward motion

Ahuja, K. K.; Massey, Kevin; D’Agostino, M.

doi:10.2514/6.1998-2359

Cited by 35 publications

(23 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, with a single-tab, 84% of the sources were located between 1 and 6 x/D and with two tabs, 82% were located between 2 and 7 x/D. These results are in agreement with the measurements of Ahuja et al (1998). They found the sound origins moved significantly upstream from a range of 4 to 8 x/D for a baseline jet to between 2 and 3 x/D for a jet with two rectangular, pointed tabs (the tabs were mounted normal to the jet centerline).…”

Section: Acoustic Measurementssupporting

confidence: 82%

“…By using the correlation between velocity fluctuations inside the jet and the far-field acoustic pressure, the noise source region of a Mach number 0.98 jet was determined to be between 5 and 10 jet diameters downstream of the jet exit (Schaffar, 1979). By utilizing various microphone arrays, several research groups have found that the highfrequency noise from high subsonic jets is generated near the nozzle exit, while lower-frequency noise originates fiirther downstream (Fisher et al, 1977, Ahuja et al, 1998and Simonich et al, 2001.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mixing and Noise in High Speed Axisymmetric Jets

Samimy¹,

Hileman²,

Caraballo³

2003

View full text Add to dashboard Cite

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searchint the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestioi AFRL-SR-AR-TR-04-.02JZS]Final Technical Report (15 Nov 99 -31 Dec 02) TITLE AND SUBTITLE Mixing and Noise in High Speed Axisymmetric Jets AUTHOR(S)M.. Samimy, J. Hileman, and E. Caraballo FUNDING NUMBERSF49620-00-1-0023 2307/AX 61102F PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Ohio This work investigated noise sources and the effects of passive mixing and noise control schemes using vortex generating tabs on noise sources. It is believed that such information is necessary for jet noise modeling and provides guidance for active control of jets for noise mitigation that will follow. The bulk of this work attempts to correlate instantaneous large-amplitude features of the far acoustic field to the dynamic evolution and interaction of large-scale structures within the mixing-layer of ideally expanded, high-speed, high Reynolds number jets. Such mformation is essential for a better understanding of jet noise sources, and jet aeroacoustic modeling and control. ABSTRACTThis work investigated noise sources and the effects of passive mixing and noise control schemes using vortex generating tabs on noise sources. It is believed that such information is necessary for jet noise modeling and provides guidance for active control of jets for noise mitigation that will follow. The bulk of this work attempts to correlate instantaneous large-amplitude features of the far acoustic field to the dynamic evolution and interaction of large-scale structures within the mixing-layer of ideally expanded, high-speed, high Reynolds number jets. Such information is essential for a better understanding of jet noise sources, and jet aeroacoustic modeling and control.The jet under study had a nozzle exit diameter of 2.54 cm, a Mach number of 1.3, and a Reynolds number of 10*. The jet was operated with and without delta tabs to better vmderstand how these noise reduction devices (when used in a chevron configuration) modify the jet and its noise generation mechanisms. Three cases are examined: a baseline (no-tab) jet, a single delta tab jet, and a dual delta tab jet. Power spectra and average acoustic waveform measurements were made for a variety of azimuthal locations; apparent noise origins were determined with an inline microphone array as well as a 3-D microphone array; and temporally resolved flow visualization was used to examine the dynamic flow structure of the jet's mixing-layer. Both of the microphone arrays are unique in they allow for the determination of the origin of individual acoustic 'events' as opposed to obtaining a time-average soimd generation region and they were both placed at an angle of 30° relative to the downstream jet axis. The development and application of both of these novel arrays are presented. Condit...

show abstract

Section: Acoustic Measurementssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Mixing and Noise in High Speed Axisymmetric Jets

Samimy¹,

Hileman²,

Caraballo³

2003

View full text Add to dashboard Cite

show abstract

“…The experiments outlined in this report used Dougherty's 5 acoustic beamforming method to obtain source location data and are superimposed in a plot of Strouhal number (fD/U) versus X/D over the data acquired by Chu et al 2 , Fisher et al 3 , and Ahuja et al 4 for subsonic jets using completely different techniques. Theoretically, the acoustic beamformer allows for a wide range of frequency sources to be found without needing to move the apparatus or run additional tests.…”

Section: A Source Locationmentioning

confidence: 98%

Measuring Jet Noise Source Locations with Acoustic Beamforming

Breen

Ahuja

2015

53rd AIAA Aerospace Sciences Meeting

View full text Add to dashboard Cite

Numerous methods have been used by the aeroacoustics community to locate noise sources of different frequencies in subsonic jets. These include: acoustic mirrors, microphone arrays, two-microphone methods, causality correlation and coherence techniques, acoustic beamforming, and automated source breakdown. Except for the acoustic beamforming, most of these methods are quite time consuming. No one seems to have ever compared the performance of these techniques. This paper compares the performance of various existing techniques. As the beamforming technique is the least time consuming, emphasis has been given to examining the performance of this technique in measuring source location in a subsonic jet for a range of Reynolds numbers. A 48-microphone acoustic beamformer was used to locate the noise sources for several subsonic Mach numbers from a one-inch and a half-inch nozzle. The effects of tabs on source location are also examined for the one-inch nozzle. Once set up, this method allows for faster and thus more numerous tests. It is shown that jet noise source locations may be a strong function of either Reynolds number or nozzle exit boundary layer. In general, there is a shift of all the noise sources away from the nozzle exit as Reynolds number decreases. Nomenclature BW = bandwidth, in Hz CF = center frequency, in Hz D = diameter of the nozzle, in inches f = source center frequency, in Hz M = Mach number U = nozzle velocity, in feet per second X = distance from the nozzle exit, in inches

show abstract

“…4), the two microphone minimum phase method (ref. 5), and the phased-array beamforming method (refs. 6, 7, 14, and 15).…”

Section: Introductionmentioning

confidence: 99%