An experimental investigation of overexpanded jets with chevrons

Henderson, Brenda S.; Wernet, Mark P.

doi:10.1016/j.jsv.2015.04.020

Cited by 17 publications

(5 citation statements)

References 38 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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“…Mean and turbulence velocity measurements were made using particle image velocimetry (PIV) in a manner consistent with recent tests in NATR 10,11 . Two types of PIV measurements were performed: (1) two-component streamwise experiments and (2) cross-stream three-component PIV experiments.…”

Section: Particle Image Velocimetry (Piv)mentioning

confidence: 99%

Aeroacoustic Validation of Installed Low Noise Propulsion for NASA’s N+2 Supersonic Airliner

Bridges

2018

2018 AIAA Aerospace Sciences Meeting

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An aeroacoustic test was conducted at NASA Glenn Research Center on an integrated propulsion system designed to meet noise regulations of ICAO Chapter 4 with 10EPNdB cumulative margin. The test had two objectives: to demonstrate that the design meets the noise goal and to validate the noise prediction tools used during the design process. Variations in the propulsion system design and its installation were tested and the results compared against predictions. Far-field microphones measured the acoustic spectral directivity, which was transformed to full scale and used to compute noise certification levels. Phased array measurements confirmed that the shielding of the installation model adequately simulated the full aircraft and provided data for validating RANS-based noise prediction tools. Particle image velocimetry confirmed that the flow field around the nozzle on the jet rig mimicked that of the full aircraft and produced flow data to validate the RANS solutions used in the noise predictions. The far-field acoustic measurements confirmed the empirical predictions for the noise. Results provided here detail the steps taken to ensure accuracy of the measurements and give insights into the physics of exhaust noise from installed propulsion systems in future supersonic vehicles. Nomenclature h E standoff height of planform from nozzle lipline k flight exponent Ma acoustic Mach Number; jet velocity divided by ambient speed of sound M flight Ambient Mach number or flight speed U mean velocity x E length of planform from nozzle to trailing edge b denotes bypass stream c denotes core stream t denotes tertiary stream

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“…When employing the notched nozzle, the shock spacing remains nearly constant. [16][17][18] A screech may damage the BBSAN because the shocks in a screeching jet oscillate at the screech frequency. In an azimuthal mode analysis, BBSAN generates high-frequency near-field and far-field noise.…”

Section: Introductionmentioning

confidence: 99%

Supersonic jet noise and screech tone suppression using cross-wire

Periyasamy,

Parthasarathy Natarajan

2023

International Journal of Aeroacoustics

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This experimental investigation is aimed at assessing how the introduction of a cross-wire at the exit of a CD nozzle influences the performance of a supersonic nozzle. The study focuses on cold air jets generated by De Laval nozzles equipped with cross-wires and baseline configurations, particularly at design Mach numbers of 1.5 and 1.75. The investigation involves collecting measurements from the noise field emitted by the cross-wire nozzle with a 2% obstruction at the exit. This passive control approach effectively reduces the occurrence of screech tones in both over-expanded and under-expanded conditions in the azimuthal plane at appropriate operating pressures. Various acoustic parameters, including sound pressure levels (SPL), Strouhal numbers, and the overall sound pressure level spectra (OASPL) are recorded. Schlieren imaging captures images of shock cell patterns, illustrating the impact of shock-associated noise. In comparison to a baseline nozzle, the results demonstrate that a CD nozzle equipped with a cross-wire proves to be a proficient screech tone suppressor, leading to an average reduction of up to 5 dB in OASPL in under-expanded and over-expanded scenarios.

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An experimental investigation of overexpanded jets with chevrons

Cited by 17 publications

References 38 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

Aeroacoustic Validation of Installed Low Noise Propulsion for NASA’s N+2 Supersonic Airliner

Supersonic jet noise and screech tone suppression using cross-wire

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