Impact of chevron spacing and asymmetric distribution on supersonic jet acoustics and flow

Heeb, Nick; Gutmark, Ephraim; Kailasanath, K.

doi:10.1016/j.jsv.2016.01.047

Cited by 20 publications

(11 citation statements)

References 64 publications

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“…This concept evolved into the modern chevron design, which has been the topic of many more recent studies. [130][131][132][133][134][135][136][137][138] While chevron technology has offered a sufficiently attractive trade-off between noise and thrust to justify their inclusion on a number of modern engines, a full phenomenological explanation of the mechanism by which they achieve this trade-off is yet lacking. From the perspective of screech, however, it seems likely that chevrons suppress resonance in much the same manner as tabs and notches: some combination of reduced hydrodynamic growth rates, reduced shock strength and reduced receptivity.…”

Section: Passive Flow Controlmentioning

confidence: 99%

Aeroacoustic resonance and self-excitation in screeching and impinging supersonic jets – A review

Edgington-Mitchell

2019

International Journal of Aeroacoustics

172

104

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Supersonic jets, particularly shock-containing jets, often exhibit high-intensity, discrete-frequency acoustic tones. These tones are the signature of an aeroacoustic resonance loop established by the flow. This paper considers two of the classical forms of supersonic jet resonance: screech in shock-containing free jets and tones generated by the impingement of a jet against a surface. The first half of the paper provides a historical perspective on research into both forms of resonance, ranging from the seminal works of Alan Powell to recent contributions from high-fidelity numerical simulation, experiment, and stability theory. The second half of the paper provides a critical assessment of current understanding around the four processes that characterize jet resonance: a downstream propagation of energy, an acoustic generation mechanism, an upstream propagation of energy, and a receptivity mechanism.

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Section: Passive Flow Controlmentioning

confidence: 99%

Aeroacoustic resonance and self-excitation in screeching and impinging supersonic jets – A review

Edgington-Mitchell

2019

International Journal of Aeroacoustics

172

104

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“…2 was centred at the nozzle origin with a radius of 48D. Note that Viswanathan [24] had earlier suggested that a microphone distance of approximately 35D is sufficient for fair-field jet noise measurements, and that distances ranging from 47D to 49D for relatively similar far-field measurements have been adopted by Wlezien and Kibens [18], Heeb et al [25] and Munday et al [26] previously.…”

Section: Far-field Acoustic Measurementsmentioning

confidence: 99%

“…When the NPR increases from 4 to 5, the amplitudes and frequency of the density gradient oscillations can be seen to increase and decrease respectively. Since the average shock strength can be evaluated by averaging difference between adjacent peak and valley amplitudes [25,50], the average peak- Figure 19 presents a comparison of density gradient profiles between baseline, S30 and S60 nozzles at different azimuthal planes. The results indicate that the density gradient profiles of the two stepped nozzles do not demonstrate regular oscillatory patterns, which is considered to be a direct consequence of the asymmetric shock cell structures found in the jets.…”

Section: Quantitative Calibrated Schlierenmentioning

confidence: 99%

Mitigation of under-expanded supersonic jet noise through stepped nozzles

Wei

Mariani

Chua

et al. 2019

Journal of Sound and Vibration

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“…Both passive and active jet control methods have been researched and used in a variety of aerospace applications. Passive jet control methods used either geometrical modifications of the nozzle like use of cross wire, 1,2 notches, 3,4 tabs, [5][6][7] chevrons, [8][9][10] grooves, 11,12 expansion ramps, 13,14 or modifying the exit shape. [15][16][17][18][19] Active control methods employed some kind of actuator assisted device to interact with the jet to achieve jet control by changing the jet structure dynamically.…”

Section: Introductionmentioning

confidence: 99%

Effect of flat wall length on decay and shock structure of a supersonic square wall jet

Tammabathula

Ghanta

Bandla

2021

Proceedings of the Institution of Mechanical Engineers, Part G:

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Experiments were conducted to find the effect of wall length on the decay behaviour and shock structure of a supersonic wall jet issuing from c-d nozzle of the square-shaped exit. A straight flat wall of width same as the side length of the square was attached to the lip of the nozzle such that the leading edge of the wall and the side of the square aligned properly which allowed the supersonic jet to graze past the flat wall. Experiments were conducted with five different wall lengths, that is, [Formula: see text] = 0.5, 1, 2, 4 and 8. Wall pressure measurements were made from leading edge to the trailing edge of the wall along its centreline. Schlieren flow visualization of the jet flow over the wall for the different wall lengths revealed the shock pattern and the effect of the wall length on the shock structure. The shock structure and jet deflection were significantly affected due to the presence of the wall. There was an upward jet deflection for [Formula: see text] up to [Formula: see text] whereas a downward jet deflection was observed for [Formula: see text]. Noticeable changes in the shock structure were observed for the wall lengths up to 2 D h. The wall length also significantly affected the jet decay characteristics and supersonic core length. Maximum enhancement in jet decay and maximum reduction in supersonic core length resulted when the wall length was [Formula: see text]. However, when the wall length was increased to [Formula: see text], there was a significant reduction in jet decay and a recovery of [Formula: see text]. Presence of wall always resulted a reduction in Lsc irrespective of wall length. The wall effect was to induce a more precipitous pressure drop closer to the nozzle exit, and a more gradual drop farther from it for [Formula: see text] > [Formula: see text].

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Impact of chevron spacing and asymmetric distribution on supersonic jet acoustics and flow

Cited by 20 publications

References 64 publications

Aeroacoustic resonance and self-excitation in screeching and impinging supersonic jets – A review

Aeroacoustic resonance and self-excitation in screeching and impinging supersonic jets – A review

Mitigation of under-expanded supersonic jet noise through stepped nozzles

Effect of flat wall length on decay and shock structure of a supersonic square wall jet

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