Shock structures and instabilities formed in an underexpanded jet impinging on to cylindrical sections

Mason-Smith, Nicholas; Edgington-Mitchell, Daniel; Buchmann, Nicolas; Honnery, Damon; Soria, Julio

doi:10.1007/s00193-015-0561-8

Cited by 31 publications

(14 citation statements)

References 22 publications

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“…There is also a high-pressure region in the impingement zone as a stagnation occurrs and a stand-off shock is formed. A streamwise modulation in all three variables is observed, similar to the modulations reported in previous experimental and numerical studies [4][5][6]12,20,[48][49][50][51]. The second-order statistics are also examined.…”

Section: Characteristics Of the Flow-fieldsupporting

confidence: 84%

“…In both mechanisms, the main parts of the feedback loop are the shear layer instabilities propagating downstream and pressure waves propagating upstream. The shear layer instabilities form unstable spatially growing hydrodynamic waves, and have been observed in previous experimental and numerical studies of free and impinging under-expanded supersonic jets [2,[4][5][6][7][8][9][10]. There is a common belief that the acoustic waves scattered by the nozzle lip through the receptivity process internalise as shear layer Kelvin-Helmholtz-type instabilities and form these coherent structures [2,11,12].…”

Section: Introductionmentioning

confidence: 76%

“…There is a common belief that the acoustic waves scattered by the nozzle lip through the receptivity process internalise as shear layer Kelvin-Helmholtz-type instabilities and form these coherent structures [2,11,12]. The near-field acoustic fields of these flows have also been studied experimentally [2,4,6,7,10], where the upstream propagating acoustic waves were visualised using the Schlieren technique. What is known about the feedback loop is largely based on these observations, but the connection between the formation of the coherent structures and sound generation are not well understood.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of Coherent Structures in an Under-Expanded Supersonic Impinging Jet Using Spectral Proper Orthogonal Decomposition (SPOD)

Karami

Soria

2018

Aerospace

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The spatiotemporal dynamics of the coherent structures in an under-expanded supersonic impinging jet are studied using a spectral proper orthogonal decomposition technique. For this analysis, a large eddy simulation of an under-expanded supersonic impinging jet at a pressure ratio of 3.4 and a stand-off distance of 2 jet diameters at a Reynolds number of 50,000 is performed. The mean flow fields illustrate some striking features of this flow, such as an oblique shock, a stand-off shock, a Mach disk, and a recirculation bubble. The spectral proper orthogonal decomposition method is applied to time-resolved three-dimensional flow fields. The accumulative energy of modes within each azimuthal mode number reveals that the first three azimuthal modes contain most of the energy of the flow. The spectra of these azimuthal modes show that the flow exhibits a low-ranked behaviour with discrete frequencies at the optimal symmetric azimuthal mode while other two azimuthal modes have negligible contributions in this behaviour. Three peaks are observed in the spectra of the optimal symmetric azimuthal mode. The spatial fields of the streamwise velocity and pressure of these peaks show that the complex structures are consequences of the under-expansion, Mach disk, and the impingement. Strong hydrodynamic instabilities exist in the shear layer of the jet in the optimal azimuthal mode at each of these dominant frequencies. High-amplitude acoustic waves are also present in the near-field of the jet. These acoustic waves are strong at the nozzle lip, suggesting that a feedback loop linking these two processes exists for dominant frequencies in the optimal mode. High cross-spectrum density of near-field pressure fluctuations and streamwise velocity fluctuations near the nozzle lip at these frequencies confirms the hydro-acoustic coupling, which is necessary to close the feedback loop.

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Section: Characteristics Of the Flow-fieldsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of Coherent Structures in an Under-Expanded Supersonic Impinging Jet Using Spectral Proper Orthogonal Decomposition (SPOD)

Karami

Soria

2018

Aerospace

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“…Тепловые процессы при взаимодействии струи с полостью обсуждаются в работе [14]. Результаты исследований возникающих автоколебаний и акустических пульсаций, создаваемых взаимодействием струи с преградой, приводятся в работах [15][16][17][18][19][20][21][22]. При обтекании цилиндра, имеющего полость достаточно большой глубины, колебания головного скачка уплотнения происходят без существенного изменения его формы.…”

Section: Introductionunclassified

Структура Течения И Колебания Давления При Взаимодействии Сверхзвуковой Недорасширенной Струи Газа С Трубной Полостью

Волков¹,

Емельянов²,

Ефремов³

et al. 2020

Журнал Технической Физики

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Supersonic jets are widely used in devices based on the phenomenon of a self-oscillating process that occurs when a gas flow interacts with circular cavities (gas-jet sound emitters). The mechanisms of maintaining undamped pressure oscillations and determining the flow field in the tube cavity during the interaction of a supersonic underexpanded jet with cavity are considered. The physical pattern of the flow in the cavity of a gas-jet emitter is discussed, the existence of odd longitudinal modes is shown, and wave diagrams are proposed for describing the flow in odd longitudinal modes. The wave diagrams are based on the analysis of the signals of piezoelectric sensors, recording pressure oscillations in the tube cavity. The calculation of the flow parameters in the tube cavity in longitudinal modes is based on the flow velocity and speed of sound diagram.

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“…Тепловые процессы при взаимодействии струи с полостью обсуждаются в работе [4]. Результаты исследований возникающих автоколебаний и акустических пульсаций, создаваемых взаимодействием струи с преградой, приводятся в работах [5][6][7][8][9][10][11][12]. При обтекании цилиндра, имеющего полость достаточно большой глубины, колебания головного скачка уплотнения происходят без существенного изменения его формы.…”

Section: Introductionunclassified

Акустические Характеристики Автоколебательного Процесса, Возникающего При Взаимодействии Сверхзвуковой Недорасширенной Струи С Цилиндрической Полостью

Волков¹,

Емельянов²,

Ефремов³

et al. 2020

Журнал Технической Физики

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In high-pressure gas-jet emitters, the source of sound energy is kinetic energy of gas jet at supercritical pressure ratios between the working pressure and the atmospheric pressure. Under certain conditions, interaction of a supersonic jet with the resonator is accompanied by powerful self-excited oscillating process with the generation of acoustic waves into the environment and cavity resonator. A model of a self-excited oscillating process arising from the interaction of non-isobaric jet with semi-closed cylindrical cavities, allowing to distinguish typical elements of gas-dynamic structure of the forming flow, is considered. The physical pattern of the flow in the cavity of gas-jet emitter is discussed, and a study of the dependence of the characteristics of the self-excited oscillating process on the gas-dynamic and geometric parameters is performed.

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Shock structures and instabilities formed in an underexpanded jet impinging on to cylindrical sections

Cited by 31 publications

References 22 publications

Analysis of Coherent Structures in an Under-Expanded Supersonic Impinging Jet Using Spectral Proper Orthogonal Decomposition (SPOD)

Analysis of Coherent Structures in an Under-Expanded Supersonic Impinging Jet Using Spectral Proper Orthogonal Decomposition (SPOD)

Структура Течения И Колебания Давления При Взаимодействии Сверхзвуковой Недорасширенной Струи Газа С Трубной Полостью

Акустические Характеристики Автоколебательного Процесса, Возникающего При Взаимодействии Сверхзвуковой Недорасширенной Струи С Цилиндрической Полостью

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