On the preferred mode of jet instability

Petersen, Robert A.; Samet, M. M.

doi:10.1017/s0022112088002939

Cited by 106 publications

(50 citation statements)

References 22 publications

(4 reference statements)

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“…This phase opposition for the streamwise velocity is found in coherent, axisymmetric vortical structures obtained by phase averages of forced jets (Hussain & Zaman 1981;Cohen & Wygnanski 1987;Petersen & Samet 1988), and was also seen previously in unforced jets by Lau, Fisher & Fuchs (1972). An illustration of such structures is shown in figure 18(b).…”

Section: Cross-stream Planessupporting

confidence: 79%

“…Many early studies seeking to compare wavepackets in turbulent jets with stability theory involved forced jets (Crighton & Gaster 1976;Cohen & Wygnanski 1987;Petersen & Samet 1988), whose phase-locked disturbances are more easily measured experimentally. But the extension of the conclusions of such studies to their unforced counterparts is not straightforward.…”

Section: Introductionmentioning

confidence: 99%

“…The hydrodynamic waves have small amplitudes, no fixed phase reference, and their signature is therefore difficult to educe from the velocity field of unforced jets (a recent attempt has been made by Kerhervé et al 2012 using data from a large eddy simulation). The signature is, on the other hand, relatively clear in forced jets (Crow & Champagne 1971;Hussain & Zaman 1981;Cohen & Wygnanski 1987;Petersen & Samet 1988) and transitional flows, i.e. jets with laminar boundary layers at the nozzle exit (Becker & Massaro 1968;Yule 1978;Laufer & Yen 1983;Violato & Scarano 2011).…”

Section: Introductionmentioning

confidence: 99%

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Wavepackets in the velocity field of turbulent jets

et al. 2013

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We study the velocity fields of unforced, high Reynolds number, subsonic jets, issuing from round nozzles with turbulent boundary layers. The objective of the study is to educe wavepackets in such flows and to explore their relationship with the radiated sound. The velocity field is measured using a hot-wire anemometer and a stereoscopic, time-resolved PIV system. The field can be decomposed into frequency and azimuthal Fourier modes. The low-angle sound radiation is measured synchronously with a microphone ring array. Consistent with previous observations, the azimuthal wavenumber spectra of the velocity and acoustic pressure fields are distinct. The velocity spectrum of the initial mixing layer exhibits a peak at azimuthal wavenumbers m ranging from 4 to 11, and the peak is found to scale with the local momentum thickness of the mixing layer. The acoustic pressure field is, on the other hand, predominantly axisymmetric, suggesting an increased relative acoustic efficiency of the axisymmetric mode of the velocity field, a characteristic that can be shown theoretically to be caused by the radial compactness of the sound source. This is confirmed by significant correlations, as high as 10 %, between the axisymmetric modes of the velocity and acoustic pressure fields, these values being significantly higher than those reported for two-point flow-acoustic correlations in subsonic jets. The axisymmetric and first helical modes of the velocity field are then compared with solutions of linear parabolized stability equations (PSE) to ascertain if these modes correspond to linear wavepackets. For all but the lowest frequencies close agreement is obtained for the spatial amplification, up to the end of the potential core. The radial shapes of the linear PSE solutions also agree with the experimental results over the same region. The results suggests that, despite the broadband character of the turbulence, the evolution of Strouhal numbers 0.3 St 0.9 and azimuthal modes 0 and 1 can be modelled as linear wavepackets, and these are associated with the sound radiated to low polar angles.

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Section: Cross-stream Planessupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Wavepackets in the velocity field of turbulent jets

et al. 2013

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“…The impulse response has been modeled relatively well with linear stability theory that addresses the K-H instability, and the response to periodic impulses has been quasi-linearly related to the impulse response. The jet column mode has previously been explained in terms of the inflectional instability of the shear layer, 43 and the present findings support this view.…”

Section: Energy Of Pressure Response In Forced Jetsupporting

confidence: 89%

The Impulse Response of a High-Speed Jet Forced with Localized Arc Filament Plasma Actuators

Sinha

Alkandry²,

Kearney-Fischer

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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Experimental study of planar opposed jets with acoustic excitation Phys. Fluids 25, 014108 (2013) Similarity analysis of the momentum field of a subsonic, plane air jet with varying jet-exit and local Reynolds numbers Phys. Fluids 25, 015115 (2013) Electrohydrodynamic printing under applied pole-type nozzle configuration Appl. Phys. Lett. 102, 024101 (2013) Effects of fluid properties and laser fluence on jet formation during laser direct writing of glycerol solution J. Appl. Phys. 112, 083105 (2012) We present experimental and theoretical analyses of the response of high-speed, highReynolds-number, round jets to impulsive forcing with arc-filament-plasma actuators. The impulse response is obtained with forcing Strouhal numbers, based on the nozzle exit diameter and exit center line velocity, less than 0.1. The resulting phase-averaged near-field pressure signature displays a compact wave with a positive peak preceding a negative one, indicative of a large scale structure in the shear layer of the jet. Scaling laws derived by operating the jet at four subsonic Mach numbers are used to distinguish this hydrodynamic component of the phase-averaged jet response from the direct actuator noise. As the forcing frequency increases, the compact waves in the near-field pressure signal overlap each other, indicating interaction of the growing seeded structures. For this regime, the phase-averaged response is approximately replicated by linear superposition of the impulse response, thereby demonstrating the quasi-linearity of structure interaction. A novel application of linear parabolized stability theory yields a successful model of the impulse response. C 2012 American Institute of Physics.[http://dx

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“…At x/h = 8, some prominent frequencies exist (fd/(u H2 -u ∞ ) ~ 0.15, 0.3, etc.). The value of fd/(u H2 -u ∞ ) = 0.3 is close to the frequency of preferred mode appearing in the free jet 16) . The value of fd/(u H2 -u ∞ ) = 0.15, which is about half of the larger prominent frequency, is considered to represent the vortex merging.…”

Section: Boundary Conditionssupporting

confidence: 54%

Large-Eddy Simulation of Fuel Mixing Using Streamwise Vortices in a Supersonic Flow

Watanabe

Takita

Sunami

2012

AEROSPACE TECHNOLOGY JAPAN

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Turbulent mixing field of hydrogen jets injected in supersonic streamwise vortices was numerically investigated using large-eddy simulation (LES). The jet and the streamwise vortices were introduced in a similar and simplified manner to those introduced by the alternating-wedge (AW) strut injector. The LES reproduced the large-scale wavy jet structure containing small-scale vortices as those observed in the past experiment of the AW strut. The streamwise vortices strongly promoted the jet spreading and the turbulent transition. Downstream of the turbulent transition, the fully developed turbulent state was achieved in the wavy jet structure. The instantaneous and time-averaged mixing efficiencies were quantitatively evaluated and compared each other to investigate the intermittency of mixing state. The mixing efficiency rapidly increased by the turbulent transition. The jet mixing in the streamwise vortices had lower intermittency compared to the transverse jet from the wall. The effects of the incident shock wave across the hydrogen jet were also investigated in detail. The turbulent properties such as the fluctuation intensity and the power spectrum hardly changed by the crossing of oblique shock wave. The mixing efficiency slightly increased after the oblique shock wave passed through the hydrogen jet.

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On the preferred mode of jet instability

Cited by 106 publications

References 22 publications

Wavepackets in the velocity field of turbulent jets

Wavepackets in the velocity field of turbulent jets

The Impulse Response of a High-Speed Jet Forced with Localized Arc Filament Plasma Actuators

Large-Eddy Simulation of Fuel Mixing Using Streamwise Vortices in a Supersonic Flow

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