An improved model for conventional and inverted-velocity-profile coannular jet noise

Stone, James R.; Zola, C. L.; Clark, B. J.

doi:10.2514/6.1999-78

Cited by 9 publications

(15 citation statements)

References 9 publications

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“…This approach, in conjunction with the analytically modeled convection effect in Eq. (1), correlates the variation of SPL with frequency and angle rather well, as shown earlier [3][4][5][6][7] . When comparisons are made with experimental data, it must be accounted for that noise measurements are typically made at a distance far enough from the engine/model to be in the far field of any individual noise source region, but not far enough away to treat the entire exhaust plume as a point source at the center of the nozzle exit plane, as is usually assumed in determining the directivity angle.…”

Section: Features Of Modelmentioning

confidence: 86%

“…The convection coefficient k has been taken as 3 in our past work; our current model uses k = 4. In our earlier work [4][5] we have assumed α = 0.2, but it now appears that α = 0.3, and this is incorporated in the model. The effective velocity for noise generation, V e , is in most cases calculated as follows:…”

Section: Features Of Modelmentioning

confidence: 99%

“…3 Similar methods were then applied to internal mixer nozzles in a brief study not yet reported. Next earlier separate models for conventional and inverted-velocity-profile coannular jets were coupled together, 4 and along with the 2DME code, were utilized to investigate suppression requirements and approaches for a supersonic business jet. 5 With temporarily declining interest in supersonic aircraft, the emphasis switched to high-bypass ratio coannular nozzles, including the effects of nozzle exit chevrons.…”

Section: Introductionmentioning

confidence: 99%

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Initial Development and Calibration of a Design Guide for Jet Noise Reduction

Stone

Berton

Krejsa

et al. 2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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Section: Features Of Modelmentioning

confidence: 86%

Section: Features Of Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Initial Development and Calibration of a Design Guide for Jet Noise Reduction

Stone

Berton

Krejsa

et al. 2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

Self Cite

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“…Several empirical methods have been proposed since the mid-1970s; for a brief list of these, see Balsa and Gliebe, 3 Stone et al, [4][5][6] Pao, 7 Tanna and Morris, 8 Lu, 9 the SAE method, 10 which incorporates the formulation of Lu, 9 and Fisher et al 11,12 In general, several source regions are envisioned and the noise from each is estimated using theoretical and empirical considerations. For example, Lighthill's acoustic analogy with some modifications is used in the formulation by Stone et al [4][5][6] In the model developed by Lu, 9 three source regions are thought to be important: (1) the outer shear layer between the fan and ambient flows, (2) the inner shear layer between the core and fan streams, and (3) the fully mixed jet farther downstream from the nozzle exit plane.…”

Section: Introductionmentioning

confidence: 99%

“…Several empirical methods have been proposed since the mid-1970s; for a brief list of these, see Balsa and Gliebe, 3 Stone et al., 4–6 Pao, 7 Tanna and Morris, 8 Lu, 9 the SAE method, 10 which incorporates the formulation of Lu, 9 and Fisher et al. 11,12 In general, several source regions are envisioned and the noise from each is estimated using theoretical and empirical considerations.…”

Section: Introductionmentioning

confidence: 99%

Progress in prediction of jet noise and quantification of aircraft/engine noise components

Viswanathan

2018

International Journal of Aeroacoustics

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The bypass ratio of newer turbofan engines has been increasing steadily and has reached $10; even higher bypass ratios are being considered for improving aircraft fuel efficiency. An accurate method for the prediction of jet noise over a wide range of bypass ratio, from $5 to ultra-high bypass ratios ($20), is required to address current and future needs. The main objective of the current study is the development of a procedure for real-world application that would permit the accurate prediction of jet noise, which in turn would enable the quantification of the non-jet noise component. A new empirical method for prediction of noise from realistic dual-stream jets is developed and validated against an extensive database acquired at model scale; the range of validity covers a velocity ratio (V s /V p) ! $0.6, as this is the range of interest in real turbofan engines. Accurate absolute spectral predictions at all angles and all cycle conditions are first demonstrated at model scale. The same method is then extended to full-scale predictions, both from static engine tests and airplane flyover tests. The range of Strouhal number of interest in full-scale tests spans $0.1 to $100. Nearfield effects on the jet noise from dual-stream jets have been quantified and a simple and improved procedure for incorporating spectral effects has been developed. Accurate spectral predictions are obtained for noise from static engine tests and flyover tests, over a wide range of engine operating conditions and bypass ratio. Therefore, the good quality and accuracy of the new prediction method have been confirmed at both model scale and full scale, with and without forward flight. An absolute prediction takes $1 s on a workstation, as only a single scaling equation is utilized. The application of the new prediction method in gaining better quantification and understanding of the non-jet noise components, and their reduction, is described.

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Parametric study of noise from dual-stream nozzles

Viswanathan¹

2004

J. Fluid Mech.

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A detailed parametric study of the noise from dual-stream jets has been carried out to assess the importance of the noise generated by the primary and secondary shear layers and their principal radiation directions under different operating conditions. Realistic geometries and engine conditions are chosen to enhance the relevance and the usefulness of the experimental results reported here. The effects of different operating conditions in the two streams on both the turbulent mixing noise and shock-associated noise are evaluated under static conditions as well as in the presence of an external co-flowing stream. The results indicate that the secondary-to-primary jet velocity ratio is an important parameter for mixing noise while its effect is negligible on shock-associated noise. The shock-associated noise, not surprisingly, is dependent on the geometric details of the nozzle. The characteristics of this noise component are very different depending on whether shocks are present in the primary or secondary stream. There is strong radiation of shock noise to the aft angles when the secondary stream is supersonic. This trend is troublesome since this component is transmitted into the aft cabin of certain aircraft with engines mounted close to the fuselage. The intensity of the shock-associated noise at the lower angles, in general, is proportional to the strength of the shocks and scales with ($M_{p}^{2}$ – $M_{d}^{2})^{2}$ or ($M_{s}^{2}$ – $M_{d}^{2})^{2 }$ ($M_{p}$ and $M_{s}$ denote the Mach numbers of the primary and secondary streams and $M_{d}$ is the design Mach number). Just as for a single jet, the effect of forward flight on mixing noise and shock-associated noise is very different. While there is a progressive reduction in levels of mixing noise with increasing free-stream velocity, there is amplification of the shock-associated noise. This is particularly so for the aft-radiated component of shock noise from the secondary stream. This effect could further exacerbate the interior noise in the aft cabin.

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An improved model for conventional and inverted-velocity-profile coannular jet noise

Cited by 9 publications

References 9 publications

Initial Development and Calibration of a Design Guide for Jet Noise Reduction

Initial Development and Calibration of a Design Guide for Jet Noise Reduction

Progress in prediction of jet noise and quantification of aircraft/engine noise components

Parametric study of noise from dual-stream nozzles

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