Experimental Investigation of Near-Field Pressure Fluctuations Generated by Supersonic Jets

Kuo, Ching Wen; Buisson, Quentin; McLaughlin, Dennis K.; Morris, Philip J.

doi:10.2514/6.2013-2033

Cited by 30 publications

(11 citation statements)

References 29 publications

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“…The importance of evanescent wave components in the full-scale jet near field is not yet clear, but in a recent study of supersonic jets by Kuo et al (2013), it was demonstrated that the acoustic (propagating) components of the spectra dominate the near field in the upstream region where convective turbulence velocities are supersonic, and the hydrodynamic (evanescent) components dominate downstream where the local convective velocities become subsonic. The competing components of acoustic and hydrodynamic pressures in the near field of a full-scale jet, and their relation to the geometrical spreading in the transition region from the near to the far field, are worth further investigation.…”

Section: Introductionmentioning

confidence: 99%

Cylindrical acoustical holography applied to full-scale jet noise

Wall

Gee

Neilsen

et al. 2014

The Journal of the Acoustical Society of America

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Near-field acoustical holography methods are used to predict sound radiation from an engine installed on a high-performance military fighter aircraft. Cylindrical holography techniques are an efficient approach to measure the large and complex sound fields produced by full-scale jets. It is shown that a ground-based, one-dimensional array of microphones can be used in conjunction with a cylindrical wave function field representation to provide a holographic reconstruction of the radiated sound field at low frequencies. In the current work, partial field decomposition methods and numerical extrapolation of data beyond the boundaries of the hologram aperture are required prior to holographic projection. Predicted jet noise source distributions and directionality are shown for four frequencies between 63 and 250 Hz. It is shown that the source distribution narrows and moves upstream, and that radiation directionality shifts toward the forward direction, with increasing frequency. A double-lobe feature of full-scale jet radiation is also demonstrated.

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Section: Introductionmentioning

confidence: 99%

Cylindrical acoustical holography applied to full-scale jet noise

Wall

Gee

Neilsen

et al. 2014

The Journal of the Acoustical Society of America

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show abstract

“…The procedure is not straightforward in low supersonic jets, where the difference in speed between hydrodynamic and acoustic features is smaller in the potential core region. Kuo et al (2013) use empirical mode decomposition (EMD) to differentiate the two modes by extracting signal components within narrow bands of frequencies. Likewise, Sinayoko, Agarwal & Sandberg (2013) use wavenumber-frequency domain filtering to characterize trapped acoustic modes which could effectively propagate to the far field.…”

Section: S Unnikrishnan and D V Gaitondementioning

confidence: 99%

Acoustic, hydrodynamic and thermal modes in a supersonic cold jet

Nair

Gaitonde

2016

J. Fluid Mech.

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Large-eddy simulation data for a Mach 1.3 round jet are decomposed into acoustic, hydrodynamic and thermal components using Doak's momentum potential theory. The decomposed fields are then analysed to examine the properties of each mode and their dynamics based on the transport equation for the total fluctuating enthalpy. The solenoidal fluctuations highlight hydrodynamic components of the jet and capture the shear layer growth and breakdown process. The acoustic mode exhibits a jittering coherent wavepacket structure in the turbulent region and consequent highly directional downstream radiation. The expected radial decay rates, r for acoustic, are recovered and closely follow the universal radiation spectra in the sideline and downstream directions. The scalogram of the acoustic mode in the near-acoustic-field region is consistent with that of the pressure perturbation signal in the acoustic-frequency range, but effectively removes the hydrodynamic and thermal content. The time-resolved and mean behaviour of terms in the total fluctuating enthalpy equation is analysed in detail. A large-scale intermittent event in the near-acoustic field is shown to be associated with an intrusion of vortices from the shear layer into the core of the jet. Acoustic sources are created when the resulting negative fluctuations in the solenoidal component interact with positive fluctuations in the Coriolis acceleration term. The latter are associated with regions of high vorticity on the inner side of the shear layer. In contrast, sinks result from the interaction of solenoidal momentum fluctuations with positive entropy gradients along entrainment streaks.

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“…In this study, only the axisymmetric azimuthal mode n¼0 is considered. Experiments [34] and the current numerical study (although not included in the present paper) show that the higher azimuthal modes have lower amplitudes and less contribution to the far-field noise radiations. Therefore, the similarity of (Eqs.…”

Section: A Quantitative Approach To Noise Identificationmentioning

confidence: 79%

“…Successful applications have been reported both experimentally [12,34,38] and computationally [39,40].…”

Section: Appendix B Podmentioning

confidence: 95%

Experimental Investigation of Near-Field Pressure Fluctuations Generated by Supersonic Jets

Cited by 30 publications

References 29 publications

Cylindrical acoustical holography applied to full-scale jet noise

Cylindrical acoustical holography applied to full-scale jet noise

Acoustic, hydrodynamic and thermal modes in a supersonic cold jet

The separation of radiating and non-radiating near-field pressure fluctuations in supersonic jets

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