Investigation of supersonic twin-jet coupling using spatial linear stability analysis

Nogueira, Petrônio A. S.; Edgington-Mitchell, Daniel

doi:10.1017/jfm.2021.366

Cited by 35 publications

(40 citation statements)

References 56 publications

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“…In recent years, the feedback has been attributed to guided jet modes (e.g. Tam & Hu 1989; Nogueira & Edgington-Mitchell 2021), though the physics of these modes is not yet clear. Given the importance of LSS timing and organization to the screech process as well as the employed control technique, determining the appropriate method for scaling the relevant frequency is crucial.…”

Section: Baseline Resultsmentioning

confidence: 99%

“…More recently, it has been suggested that the feedback waves for screech may be due to a guided jet mode (Tam & Hu 1989; Edgington-Mitchell et al. 2018; Nogueira & Edgington-Mitchell 2021). Zaman et al.…”

Section: Baseline Resultsmentioning

confidence: 99%

“…Traditionally, feedback was assumed to be in the form of acoustic waves, propagating upstream external to the jet. More recently, it has been suggested that the feedback waves for screech may be due to a guided jet mode (Tam & Hu 1989;Edgington-Mitchell et al 2018;Nogueira & Edgington-Mitchell 2021). Zaman et al (2022) examined the signature of these guided waves in high subsonic and underexpanded jets, using microphones just outside the jets, and found they produced tonal peaks, one of which seemed to transition into the screech tone as the NPR was incrementally increased to the underexpanded flow regime.…”

Section: Screech and Coupling In Rectangular Twin Jetsmentioning

confidence: 99%

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Perturbation-based active flow control in overexpanded to underexpanded supersonic rectangular twin jets

et al. 2023

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The effects of perturbation-based active flow control on supersonic rectangular twin jets (SRTJ) over a wide range of nozzle pressure ratios (NPR = 2.77 to 6.7, corresponding to fully expanded Mach numbers Mj = 1.3 to 1.9) were investigated. The aspect ratio and design Mach number for the bi-conic, converging-diverging nozzles were 2 and 1.5, respectively. The flow and acoustic fields of SRTJ are known to couple, often generating high near-field (NF) pressure fluctuations and elevated far-field (FF) noise levels. Large-scale structures (LSS), or equivalently instability waves or wave packets, are responsible for mixing noise, broadband shock-associated noise, screech and coupling. The primary objective of this research was to manipulate the development of LSS in this complex flow to better understand and mitigate their effects. The organization and passage frequency of the LSS were altered by excitation of instabilities over a wide range of frequencies and modes. Key findings include: (1) the screech mode of each jet was flapping along its minor axis; (2) the jets coupled, out-of-phase primarily in overexpanded cases and in-phase primarily in underexpanded cases, along the minor axis of the SRTJ; (3) coupling has significant effects on the NF pressure fluctuations, but only minor effect on the FF noise; (4) standing waves were observed only on the minor axis plane of the SRTJ; (5) altering or suppressing coupling can significantly reduce NF pressure fluctuations; (6) two high-frequency excitation methods proved effective in reducing the FF noise; and (7) nonlinear interactions between the screech tones and excitation input were observed in controlled cases in which screech was only partially suppressed.

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Section: Baseline Resultsmentioning

confidence: 99%

Section: Baseline Resultsmentioning

confidence: 99%

Section: Screech and Coupling In Rectangular Twin Jetsmentioning

confidence: 99%

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Perturbation-based active flow control in overexpanded to underexpanded supersonic rectangular twin jets

et al. 2023

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“…2018; Gojon, Bogey & Mihaescu 2018; Mancinelli et al. 2019) and in supersonic twin jets (Nogueira & Edgington-Mitchell 2021). In these cases, strong aeroacoustic resonance processes, which can be isolated using the proper orthogonal decomposition method for instance (Edgington-Mitchell et al.…”

Section: Introductionmentioning

confidence: 99%

Interactions between upstream-propagating guided jet waves and shear-layer instability waves near the nozzle of subsonic and nearly ideally expanded supersonic free jets with laminar boundary layers

Bogey

2022

J. Fluid Mech.

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The interactions between upstream-propagating guided jet waves and shear-layer instability waves near the nozzle of subsonic and nearly ideally expanded supersonic, isothermal free jets are investigated for jets at Mach numbers between 0.50 and 2 with fully laminar exit boundary layers of different thicknesses. The velocity spectra in the shear layers downstream of the nozzle exhibit strong narrow peaks for the first azimuthal modes, associated with growing Kelvin–Helmholtz instability waves. The frequencies of the predominant peaks are close, but not necessarily equal, to those of the most amplified instability waves predicted from the mean flow fields using linear stability analysis. They also fall in most cases within or very near the allowable frequency bands of the free-stream upstream-propagating guided jet waves obtained using a vortex-sheet model and jump from one band to another as the Mach number increases. At these frequencies, moreover, high levels organized into elongated stripes are found in the jet potential core and standing-wave patterns are visible at the edges of the shear layers in the power spectral densities of pressure and velocity fluctuations. Therefore, the free-stream upstream-propagating guided jet waves appear to interact with and excite the instability waves near the nozzle of the present jets, as in screeching and impinging jets. This explains the disparities of the frequencies and azimuthal modes of the instability waves dominating early on in the shear layers of initially laminar jets and their discontinuous changes and staging behaviours as the jet velocity varies.

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“…2018), as well as numerically for ideally expanded (Bogey & Gojon 2017) and shock-containing (Gojon & Bogey 2017) impinging jets. Further, in a consideration of twin jets, which can exhibit a range of different coupling symmetries, it has been demonstrated that only those symmetries where the G-JM is propagative are observed in experimental data (Nogueira & Edgington-Mitchell 2021). Thus the suggestion of Shen & Tam (2002) that the G-JM might be a component of jet screech appears to have been prescient; however, they suggested that it might be active only in certain mode stages, while the present evidence suggests that the G-JM is actually the upstream component of all screech stages (Nogueira et al.…”

Section: Introductionmentioning

confidence: 99%

A unifying theory of jet screech

Edgington-Mitchell

Liu

et al. 2022

J. Fluid Mech.

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This paper describes the mechanism underpinning modal staging behaviour in screeching jets. An upstream-propagating subsonic guided-jet mode is shown to be active in all stages of screech. Axial variation of shock-cell spacing manifests in the spectral domain as a series of suboptimal peaks. It is demonstrated that the guided-jet mode may be energized by interactions of the Kelvin–Helmholtz wavepacket with not only the primary shock wavenumber peak, but also suboptimal peaks; interaction with suboptimals is shown to be responsible for closing the resonance loop in multiple stages of jet screech. A consideration of the full spectral representation of the shocks reconciles several of the classical models and results for jet screech that had heretofore been paradoxical. It is demonstrated that there are multiple standing waves present in the near field of screeching jets, corresponding to the superposition of the various waves active in these jets. Multimodal behaviour is explored for jets in a range of conditions, demonstrating that multiple peaks in the frequency spectra can be due to either changes in which peak of the shock spectra the Kelvin–Helmholtz wavepacket is interacting with, or a change in azimuthal mode, or both. The absence of modal staging in high-aspect-ratio non-axisymmetric jets is also explained in the context of the aforementioned mechanism. The paper closes with a new proposed theory for frequency selection in screeching jets, based on the observation that these triadic interactions appear to underpin selection of the guided-jet mode wavelength in all measured cases.

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Investigation of supersonic twin-jet coupling using spatial linear stability analysis

Abstract: Abstract

Cited by 35 publications

References 56 publications

Perturbation-based active flow control in overexpanded to underexpanded supersonic rectangular twin jets

Perturbation-based active flow control in overexpanded to underexpanded supersonic rectangular twin jets

Interactions between upstream-propagating guided jet waves and shear-layer instability waves near the nozzle of subsonic and nearly ideally expanded supersonic free jets with laminar boundary layers

A unifying theory of jet screech

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