Acoustically Informed Statistics for Wave-Packet Models

Nair, Unnikrishnan Sasidharan; Cavalieri, André V. G.; Gaitonde, Datta V.

doi:10.2514/1.j057938

Cited by 30 publications

(15 citation statements)

References 45 publications

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“…Higher-order modes show a behaviour different from wavepacket-like structures and are disregarded. This is in agreement with analyses by Breakey et al (2013) and Unnikrishnan, Cavalieri & Gaitonde (2019), where the results from the first SPOD mode compare well with analytical methods and experimental data. Therefore, proceeding in the investigation on the behaviour of the structures, the amplitude of mode 1 is then extracted in the axial direction for a fixed height, as shown in figure 29.…”

Section: Axial-direction Scaling Lawsupporting

confidence: 91%

Jet-installation noise and near-field characteristics of jet–surface interaction

et al. 2020

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Section: Axial-direction Scaling Lawsupporting

confidence: 91%

Jet-installation noise and near-field characteristics of jet–surface interaction

et al. 2020

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“…Doak's MPT equations are solved in cylindrical coordinates on a 2D streamwise plane for both baseline and 3FC-2FI jets. It is found that even though the 3FC-2FI jet is not axisymmetric, the acoustic mode calculated on a 2D plane reduces to scaled pressure fluctuations calculated from LES away from the shear layer, similar to the observations in [29]. This verifies that the physical form of the acoustic mode is not significantly affected by the use of only one azimuthal slice in the solution to the Poisson equations in equation (4.2).…”

Section: (D) Spectral Proper Orthogonal Decompositionsupporting

confidence: 74%

“…Unnikrishnan & Gaitonde [28] were the first investigators to use this method to study the noise generation characteristics of a perfectly expanded cold supersonic jet. Unnikrishnan et al [29] also used this method for the eduction of wavepacket structures in a cold subsonic jet and found that the acoustic mode reduces to the radiated sound field beyond the jet shear layer. Despite these efforts, the potential of Doak's theory for aeroacoustic applications has not been explored completely.…”

Section: Introductionmentioning

confidence: 99%

Effect of fluid injection on turbulence and noise reduction of a supersonic jet

Prasad

Morris

2019

Phil. Trans. R. Soc. A.

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Supersonic jets, such as the ones used in high-performance military aircraft, have both downstream and upstream noise components due to the large-scale turbulent structures and the presence of shock cells in the jet plume. The fluid insert technology is a noise reduction method that has been shown to effectively reduce both these noise components. This paper analyses the unsteady flow changes associated with different fluid insert configurations with a goal of helping to understand the detailed noise reduction mechanisms. Using direct cross-correlations of the near-field data with the far-field microphone signals, it is found that even the use of a single injector as a fluid insert helps break up the large-scale structures of the flow. However, a more azimuthally distributed blowing is required to reduce the upstream broadband shock-associated noise (BBSAN). Addition of upstream injectors at each azimuthal location further enhances the BBSAN reduction. Decomposition of the jet flow-field into hydrodynamic and acoustic modes shows that fluid insert nozzles reduce the amplitude and convection speed of the coherent acoustic mode in the plane of highest noise reduction. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.

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“…These axially extended structures have been used extensively for predicting noise radiated from subsonic (Reba, Narayanan & Colonius 2010; Cavalieri et al. 2012; Unnikrishnan, Cavalieri & Gaitonde 2019), supersonic (Tam & Burton 1984; Wu 2005; Sinha et al. 2014) and installed (Piantanida et al.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, turbulent mixing noise generation mechanisms in jets have been associated with spatiotemporally coherent structures known as wavepackets. These axially extended structures have been used extensively for predicting noise radiated from subsonic (Reba, Narayanan & Colonius 2010;Cavalieri et al 2012;Unnikrishnan, Cavalieri & Gaitonde 2019), supersonic (Tam & Burton 1984;Wu 2005;Sinha et al 2014) and installed (Piantanida et al 2016) jet flows. A thorough summary on the topic can be found in the review by , and the relationship to resolvent modes is discussed in detail by .…”

Section: Introductionmentioning

confidence: 99%