Coherent large-scale structures in high Reynolds number supersonic jets

Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Burrin, R. H.

doi:10.2514/3.9799

Cited by 46 publications

(14 citation statements)

References 5 publications

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“…Since the probe's frequency response is of order 60 kHz, these data are well within its dynamic range and can be considered reliable. This result is consistent with earlier work by Lepicovsky et al (1987), who showed that the Strouhal number, (f6/U~), for the large-scale structures in high Reynolds number supersonic jets (M~1.4) was approximately 0.4. Furthermore, there is a clear shift to higher frequencies at stations 6 and 7 which are close to (Pt)min, and below it, respectively.…”

Section: Power Spectrasupporting

confidence: 82%

Exploratory study of turbulent structure of a compressible shear layer using fluctuating pitot pressure measurements

Shau

Dolling

1992

Experiments in Fluids

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An experimental study has been conducted to determine if two-point fluctuating pitot pressure measurements can be used to detect and quantify the large-scale structures in a two-dimensional, high Reynolds number, supersonic, turbulent shear layer. There is evidence from the two-point correlations of fluctuating pitot pressures and from the VITA analysis that large-scale structures exist and span the thickness of the shear layer. Because the shear layer exhibits a wake-like character, the large-scale structure in the lower part of the shear layer is essentially normal to the flow direction. Power spectra measured at about 25 initial shear layer thicknesses downstream of the origin are broadband, which suggests that the large-scale structures are not yet highly organized.

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Section: Power Spectrasupporting

confidence: 82%

Exploratory study of turbulent structure of a compressible shear layer using fluctuating pitot pressure measurements

Shau

Dolling

1992

Experiments in Fluids

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“…There have been a few experiments which used active control in supersonic jets (e.g. Troutt & McLaughlin 1982;Morrison 1983;Ahuja and Blakney 1985;Ahuja and Whiffen 1985;Lepicovsky et al 1985a;Lepicovsky, Ahuja & Burrin 1985b). The most relevant conclusion of these works is that both subsonic and supersonic jets support the existence of large turbulence structures; even in the presence of shocks.…”

Section: Flow Controlmentioning

confidence: 96%

A study of Mach wave radiation using active control

2011

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Mach wave radiation is one of the better understood sources of jet noise. However, the exact conditions of its onset are difficult to determine and the literature to date typically explores Mach wave radiation well above its onset conditions. In order to determine the conditions for the onset of Mach wave radiation and to explore its behaviour during onset and beyond, three ideally expanded jets with Mach numbers M j = 0.9, 1.3 and 1.65 and stagnation temperature ratios ranging over T o /T ∞ = 1.0-2.5 (acoustic Mach number 0.83-2.10) were used. Data are collected using a far-field microphone array, schlieren imaging and streamwise two-component particle image velocimetry. Using arc filament plasma actuators to force the jet provides an unprecedented tool for detailed examination of Mach wave radiation. The response of the jet to various forcing parameters (combinations of one azimuthal mode m = 0, 1 and 3 and one Strouhal number St DF = 0.09-3.0) is explored. Phaseaveraged schlieren images clearly show the onset and evolution of Mach wave radiation in response to both changes in the jet operating conditions and forcing parameters. It is observed that Mach wave radiation is initiated as a coalescing of the near-field hydrodynamic pressure fluctuations in the immediate vicinity of the large-scale structures. As the jet exit velocity increases, the hydrodynamic pressure fluctuations coalesce, first into a curved wavefront, then flatten into the conical wavefronts commonly associated with Mach wave radiation. The results show that the largest and most coherent structures (e.g. forcing with m = 0 and St DF ∼ 0.3) produce the strongest Mach wave radiation. Conversely, Mach wave radiation is weakest when the structures are the least coherent (e.g. forcing with m = 3 and St DF > 1.5).

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“…At this point, on average, the mixed ambient/freestream fluid has reached the center of the jet. Lepicovsky et al (1987) measured the centerline velocity of a Mach number 1.38, Reynolds number 1.6x10^ jet using a laser velocimeter, and found it started to deviate from a constant value between 5 and 7 D. Other researchers (Yu and Dosanjh, 1972, Thies and Tarn, 1996, Seiner, 1992) measured a similar value for the end of the potential core within a Mach 1.5 jet.…”

Section: Jet Flow Interrogationmentioning

confidence: 81%

Mixing and Noise in High Speed Axisymmetric Jets

Samimy¹,

Hileman²,

Caraballo³

2003

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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...

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Coherent large-scale structures in high Reynolds number supersonic jets

Cited by 46 publications

References 5 publications

Exploratory study of turbulent structure of a compressible shear layer using fluctuating pitot pressure measurements

Exploratory study of turbulent structure of a compressible shear layer using fluctuating pitot pressure measurements

A study of Mach wave radiation using active control

Mixing and Noise in High Speed Axisymmetric Jets

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