Modeling Far-field Acoustical Nonlinearity from F-35 Aircraft during Ground Run-up

Reichman, Brent O.; Wall, Alan T.; Gee, Kent L.; Neilsen, Tracianne B.; Downing, J. Micah; James, Michael M.; McKinley, Richard L.

doi:10.2514/6.2016-1888

Cited by 6 publications

(10 citation statements)

References 21 publications

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“…4. More engine conditions may be seen in James et al [20] for the F-35B, which is acoustically similar to the F-35A shown here [29]. In addition to the increase in OASPL seen at higher engine conditions, a shift in directivity is also observed.…”

Section: A Oasplsupporting

confidence: 85%

“…As an introduction to shock formation due to nonlinear propagation, normalized waveforms are considered ( Fig. 2), at distances of 19,29,38,76, and 152 m along the 135° radial, shown as a red line in Fig. 1.…”

Section: Measurement Setupmentioning

confidence: 99%

“…Many of these algorithms are based on the generalized Burgers equation (GBE), which accounts for quadratic nonlinearity in an arbitrary waveform while also incorporating atmospheric absorption and geometric spreading. These algorithms have been shown to accurately capture many aspects of the pressure waveform, in addition to spectral effects due to nonlinear propagation [29,30]. A hybrid time-frequency domain algorithm is used; the same model was used by Reichman et al [29] to model spectral changes due to nonlinear propagation.…”

Section: Numerical Modelingmentioning

confidence: 99%

“…These algorithms have been shown to accurately capture many aspects of the pressure waveform, in addition to spectral effects due to nonlinear propagation [29,30]. A hybrid time-frequency domain algorithm is used; the same model was used by Reichman et al [29] to model spectral changes due to nonlinear propagation. That paper successfully showed the influence of nonlinear propagation for high-frequency energy in the far field of an F-35B, in particular in a comparison between measured data and linear and nonlinear predictions.…”

Section: Numerical Modelingmentioning

confidence: 99%

“…Some disagreement is seen in the low-frequency regime due to multi-path interference effects. Though this discrepancy can be empirically corrected in the frequency domain [29], the focus of this paper is time-domain features, which are more difficult to correct for such effects. Above 400 Hz, both spectra agree remarkably well.…”

Section: A Waveform Characteristicsmentioning

confidence: 99%

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Acoustic Shock Formation in Noise Propagation During Ground Run-Up Operations of Military Aircraft

Reichman

Gee

Neilsen

et al. 2017

23rd AIAA/CEAS Aeroacoustics Conference

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A distinctive feature of many propagating, high-amplitude jet noise waveforms is the presence of acoustic shocks. Metrics indicative of shock presence, specifically the skewness of the time derivative of the waveform, the average steepening factor, and a new wavelet-based metric called the shock energy fraction (SEF), are used to quantify the strength and prevalence of acoustic shocks within waveforms recorded 10-305 m from a tethered military aircraft. The derivative skewness is more sensitive to the presence of the largest and steepest shocks, while the ASF and SEF tend to emphasize aggregate behavior of the entire waveform. These metrics are applied at engine conditions ranging from 50% to 150% engine thrust request, over a wide range of angles and distances, to assess the growth and decay of shock waves. The responses of these metrics point to significant shock formation occurring through nonlinear propagation out to 76 m from the microphone array reference position. Although these strongest shocks decay, the metrics point to continued nonlinear propagation in the far-field, out to 305 m. Many of these features are accurately characterized using a nonlinear propagation scheme based on the Burgers equation, but this scheme fails to account for multipath interference and significant atmospheric effects over the long propagation distances, resulting in an overestimation of nonlinearity metrics.

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Section: A Oasplsupporting

confidence: 85%

Section: Measurement Setupmentioning

confidence: 99%

Section: Numerical Modelingmentioning

confidence: 99%

Section: Numerical Modelingmentioning

confidence: 99%

Section: A Waveform Characteristicsmentioning

confidence: 99%

See 3 more Smart Citations

Acoustic Shock Formation in Noise Propagation During Ground Run-Up Operations of Military Aircraft

Reichman

Gee

Neilsen

et al. 2017

23rd AIAA/CEAS Aeroacoustics Conference

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Characterizing acoustic shocks in high-performance jet aircraft flyover noise

Reichman

Gee

Neilsen

et al. 2018

The Journal of the Acoustical Society of America

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Acoustic shocks have been previously documented in high-amplitude jet noise, including both the near and far fields of military jet aircraft. However, previous investigations into the nature and formation of shocks have historically concentrated on stationary, ground run-up measurements, and previous attempts to connect full-scale ground run-up and flyover measurements have omitted the effect of nonlinear propagation. This paper shows evidence for nonlinear propagation and the presence of acoustic shocks in acoustical measurements of F-35 flyover operations. Pressure waveforms, derivatives, and statistics indicate nonlinear propagation, and the resulting shock formation is significant at high engine powers. Variations due to microphone size, microphone height, and sampling rate are considered, and recommendations for future measurements are made. Metrics indicating nonlinear propagation are shown to be influenced by changes in sampling rate and microphone size, and exhibit less variation due to microphone height.

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