scholarly journals Supersonic Jet Noise Reductions Predicted With Increased Jet Spreading Rate

1998 ◽  
Vol 120 (3) ◽  
pp. 471-476 ◽  
Author(s):  
Milo D. Dahl ◽  
Philip J. Morris
Keyword(s):  
Supersonic Jet ◽  
Jet Noise ◽  
Spreading Rate ◽  
Operating Conditions ◽  
Instability Wave ◽  
Noise Levels ◽  
Radiation Model ◽  
Radiated Noise ◽  
Noise Radiation ◽  
Mixing Noise

In this paper, predictions are made of noise radiation from single, supersonic, axisymmetric jets. We examine the effects of changes in operating conditions and the effects of simulated enhanced mixing that would increase the spreading rate of the jet shear layer on radiated noise levels. The radiated noise in the downstream direction is dominated by mixing noise and, at higher speeds, it is well described by the instability wave noise radiation model. Further analysis with the model shows a relationship between changes in spreading rate due to enhanced mixing and changes in the far field radiated peak noise levels. The calculations predict that enhanced jet spreading results in a reduction of the radiated peak noise level.

Physics and Prediction of Supersonic Jet Noise

1994 ◽  
Vol 47 (6S) ◽  
pp. S184-S187
Author(s):  
Christopher K. W. Tam
Keyword(s):  
Supersonic Jet ◽  
Jet Noise ◽  
Supersonic Jets ◽  
Wave Radiation ◽  
Instability Wave ◽  
Empirical Constant ◽  
Supersonic Jet Noise ◽  
Turbulence Structures ◽  
Mixing Noise ◽  
Dominant Part

Both the large turbulence structures and the fine scale turbulence of the flows of supersonic jets are sources of turbulent mixing noise. At moderately high supersonic Mach numbers especially for hot jets, the dominant part of the noise is generated directly by the large turbulence structures. The large turbulence structures propagate downstream at supersonic velocities relative to the ambient sound speed. They generate strong Mach wave radiation analogous to a supersonically travelling wavy wall. A stochastic instability wave model theory of the large turbulence structures and noise of supersonic jets has recently been developed. The theory can predict both the spectrum and directivity of the dominant part of supersonic jet noise up to a multiplicative empirical constant. Calculated results agree well with measurements.

Acoustics measurements of military-style supersonic beveled nozzle jets with interior corrugations

2016 ◽  
Vol 16 (1-2) ◽  
pp. 21-43 ◽  
Author(s):  
Russell W Powers ◽  
Dennis K McLaughlin
Keyword(s):  
Noise Reduction ◽  
Acoustic Field ◽  
High Speed ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Operating Conditions ◽  
Military Aircraft ◽  
Azimuthal Dependence ◽  
Penn State ◽  
Mixing Noise

Increasingly powerful and noisy military aircraft have generated the need for research leading to the development of supersonic jet noise reduction devices. The hot, high speed supersonic jets exhausting from military aircraft during takeoff present a most challenging problem. The present study extends prior research on two methods of noise reduction. The first is the internal nozzle corrugations pioneered by Seiner et al. and the second is the beveled exit plane explored most recently by Viswanathan. A novel research idea of creating fluidic corrugations similar to the nozzle corrugations has been initiated by Penn State. To further the understanding and analysis of the fluidic corrugations, the present study focuses on the flow field and acoustic field of nozzles with two, three, and six conventional, hardwalled corrugations. The effect of the combination of the internal corrugations with a beveled nozzle is explored. The results show that significant noise reductions of over 3 dB of the mixing noise and the broadband shock-associated noise can be achieved. The combination of the beveled nozzle and the internal nozzle corrugations showed that there is less azimuthal dependence of the acoustic field than for the purely beveled nozzle. The combination nozzle was shown to reduce the noise over a wider range of polar angles and operating conditions than either the purely beveled nozzle or the purely corrugated nozzle.

Experimental Investigation on Supersonic Jet Noise

2012 ◽  
Vol 588-589 ◽  
pp. 860-863
Author(s):  
Xiao Bo Peng ◽  
Jia Ming Li ◽  
Chun Bo Hu
Keyword(s):  
Mach Number ◽  
Sound Production ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Occurrence Frequency ◽  
Correlated Noise ◽  
Experimental Conditions ◽  
Supersonic Jet Noise ◽  
Validation Criteria ◽  
Mixing Noise

A systematic study has been undertaken to quantify the effects of jet Mach number and nozzle size on the noise radiated by supersonic jets. All the tests were carried out at an experimental bench of the supersonic jet. Results indicate that the field distribution of supersonic jet screech tones is characterized with very strong directivity. Under the textual experimental conditions, if the jet Mach number remain unchanged, the diameter of nozzle throat increases gradually from 5mm to 8mm or 10mm, and the amplitude values of both the turbulent mixing noise and broadband shockwave correlated noise increase by 2-5dB, and the amplitude value change of the whistler type noise is not obvious, and the occurrence frequency of the whistler type noise decreases by more than 2000Hz; if the jet Mach number increases to 3.0 from 2.0, the amplitude value of the whistler type noise increases by more than 2dB, and the occurrence frequency of the whistler type noise decreases obviously. The experimental measurements of supersonic jet noise provide the sound production mechanism research on the supersonic jet noise with data supports and references and provide the numerical modeling of the supersonic jet noise with validation criteria.

Experimental Study of Supersonic Jet Noise Reduction With Microjet Injection

2009 ◽  
Author(s):  
Toshinori Watanabe ◽  
Ryuichi Okada ◽  
Seiji Uzawa ◽  
Takehiro Himeno ◽  
Tsutomu Oishi
Keyword(s):  
Experimental Study ◽  
Turbulent Mixing ◽  
Sound Pressure ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Pressure Level ◽  
Broadband Noise ◽  
Screech Tone ◽  
Supersonic Jet Noise ◽  
Mixing Noise

Experimental study was conducted concerning active control of supersonic jet noise with a microjet injection technique. The microjets were injected into a rectangular main jet with Mach number up to 1.49. The nozzle lip of the main jet was equipped with 44 injection holes of the microjets, whose angles against the main jet were changed as 60 and 90 degrees. From far-field sound pressure data, a significant reduction of the jet noise by several dB was found in the cases with 60 and 90 degrees of injection angles. The microjet was found to affect all components of supersonic jet noise, namely, turbulent mixing noise, shock-associated broadband noise and screech tone noise. In the results of FFT analysis, the effect of the microjet was observed in the sound pressure level of the shock-associated broadband noise, the pressure level and frequency of the screech tone noise, and average level of the turbulent mixing noise. Schlieren visualization was also made for the jet flow, and the microjet was seen to change the shock structure and shear layer behavior of the supersonic jet.

scholarly journals Towards Prediction and Control of Large Scale Turbulent Structure Supersonic Jet Noise

2009 ◽  
Author(s):  
Robert H. Schlinker ◽  
Ramons A. Reba ◽  
John C. Simonich ◽  
Tim Colonius ◽  
Kristjan Gudmundsson ◽  
...  
Keyword(s):  
Large Scale ◽  
Deterministic Model ◽  
Near Field ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Shear Layers ◽  
Instability Wave ◽  
Turbulent Structures ◽  
Turbulence Structures ◽  
Scale Turbulence

In this paper, we report on progress towards developing physics-based models of sound generation by large-scale turbulent structures in supersonic jet shear layers generally accepted to be the source of aft-angle noise. Aside from obtaining better engineering prediction schemes, the development and optimization of long term jet noise reduction strategies based on controlling instability wave generated large-scale turbulence structures in the shear layer can be more successful if based on predictive flow-noise models, rather than on build and test approaches alone. Such models, if successful, may also provide a path by which laboratory scale demonstrations can be more reliably translated to engine scale. Results show that the noise radiated by large-scale structures in turbulent jet shear layers may be modeled using a RANS based PSE method and projected to the far-field using a Kirchhoff surface approach. A key enabler in this procedure is the development of near-field microphone arrays capable of providing the pressure statistics needed to validate the instability wave models. Our framework provides, for the first time, a deterministic model that will allow understanding and predicting noise radiated by large-scale turbulence.

Analysis of Noise Reduction Obtainable from the Redesign of a Mechanical Assembly

1975 ◽  
Vol 17 (3) ◽  
pp. 155-162 ◽  
Author(s):  
M. A. Satter ◽  
G. Ahmadi
Keyword(s):  
Noise Reduction ◽  
Mathematical Formulation ◽  
Vibrational Amplitude ◽  
Mechanical Assembly ◽  
Noise Levels ◽  
Radiated Noise ◽  
Noise Radiation ◽  
Longitudinal Modes ◽  
Amplitude Spectra ◽  
Good Agreement

A mechanical assembly which has been investigated experimentally for noise reduction (1)‡ is examined analytically. The assembly is reduced to a model of two unequal masses connected by a shaft. The redesigned version is the same except for the insertion of a rubber bush which isolates the larger mass, thereby reducing radiated noise. Only the longitudinal modes in which noise radiation was known to take place are considered for mathematical formulation. Vibrational amplitude spectra are derived for any point in the models. Amplitude spectra are substituted directly into the theory of sound radiation from a piston to calculate noise levels radiated by the larger mass. Experimental results are in good agreement with those obtained theoretically.

Energy transfer mechanism of supersonic jet noise through rectangular nozzles

2017 ◽  
Vol 65 (2) ◽  
pp. 110-120 ◽  
Author(s):  
Zhe Chen ◽  
Jiu-Hui Wu ◽  
A-Dan Ren ◽  
Xin Chen ◽  
Zhen Huang
Keyword(s):  
Energy Transfer ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Transfer Mechanism ◽  
Energy Transfer Mechanism ◽  
Supersonic Jet Noise

A proposed wavy shield for suppression of supersonic jet noise utilizing reflections

2021 ◽  
Vol 20 (1-2) ◽  
pp. 4-34
Author(s):  
Reda R Mankbadi ◽  
Saman Salehian
Keyword(s):  
Large Scale ◽  
Flat Surface ◽  
Near Field ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Dominant Frequency ◽  
Wavy Surface ◽  
Initial Region ◽  
Reflected Waves ◽  
Free Jet

In this work we propose replacing the conventional flat-surface airframe that shields the engine by a wavy surface. The basic principle is to design a wavy pattern to reflect the incoming near-field flow and acoustic perturbations into waves of a particular dominant frequency. The reflected waves will then excite the corresponding frequency of the large-scale structure in the initial region of the jet’s shear layer. By designing the frequency of the reflected waves to be the harmonic of the fundamental frequency that corresponds to the radiated peak noise, the two frequency-modes interact nonlinearly. With the appropriate phase difference, the harmonic dampens the fundamental as it extracts energy from it to amplify. The outcome is a reduction in the peak noise. To evaluate this concept, we conducted Detached Eddy Simulations for a rectangular supersonic jet with and without the wavy shield and verified our numerical results with experimental data for a free jet, as well as, for a jet with an adjacent flat surface. Results show that the proposed wavy surface reduces the jet noise as compared to that of the corresponding flat surface by as much as 4 dB.

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