Journal ArticleDOI
Screech characteristics of under-expanded high aspect ratio elliptic jet
TLDR
In this article, the authors investigated the behavior and the closure mechanism of a feedback loop for the flapping mode in underexpanded supersonic jet by Schlieren imaging and near-field acoustic measurements for a high aspect ratio elliptic nozzle.Abstract:
Screeching behavior and the closure mechanism of a feedback loop for the flapping mode in under-expanded supersonic jet are investigated by schlieren imaging and near-field acoustic measurements for a high aspect ratio elliptic nozzle. Near-field measurements revealed a single screech frequency for the measured Mach number range. The cross spectrum of pressure signals shows that the upstream propagating wave is out of phase, which was identified as the asymmetric flapping mode. The proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) methods were applied to the time-resolved schlieren data to extract the coherent information associated with screech and its harmonics. The first three spatial POD modes reveal the periodic flapping of the jet and the asymmetric upstream propagation of acoustic waves. POD modes 4 and 5 identify the flow structures and acoustic wave patterns associated with the harmonics of the fundamental screech tone. The spatial DMD mode corresponds to the frequency of ∼10 kHz and exhibits the radial distortion of the jet shear layer and the acoustic radiation pattern. The interaction of the acoustic waves with the jet shear layer indicates that the upstream-traveling guided jet mode is responsible for closing the feedback loop of the flapping mode.read more
Citations
More filters
Journal ArticleDOI
A unifying theory of jet screech
Daniel Edgington-Mitchell,Xiangru Li,Nianhua Liu,Feng He,Tsz Yeung Wong,Jacob Mackenzie,Petrônio A. S. Nogueira +6 more
TL;DR: In this article , an upstream-propagating subsonic guided-jet mode is shown to be active in all stages of jet screech, and it is demonstrated that the mode may be energized by interactions of the Kelvin-Helmholtz wavepacket with not only the primary shock wavenumber peak, but also suboptimal peaks.
Journal ArticleDOI
Elliptic supersonic jet morphology manipulation using sharp-tipped lobes
TL;DR: In this paper, the authors experimentally manipulate the supersonic elliptic jet morphology by using two sharp-tipped lobes placed on either end of the minor axis in an elliptic nozzle.
Journal ArticleDOI
Reciprocating and flapping motions of unstart shock in a scramjet isolator
TL;DR: In this paper , two types of instabilities were observed in the unstart shock system: instability in the streamwise direction and instability in vertical direction with an asymmetrical effect on the pressures at the walls.
Journal ArticleDOI
Effect of tab parameters on the near-field mixing characteristics of a Mach 1.5 elliptic jet
TL;DR: In this article, the effect of delta-tabs with its apex leaning downstream on the jet mixing characteristics of a Mach 1.5 elliptic jet of aspect ratio (AR) 3.37 is reported.
Posted Content
Elliptic supersonic jet morphology manipulation using sharp-tipped lobes
TL;DR: In this paper, the authors experimentally manipulate the supersonic elliptic jet morphology by using two sharp-tipped lobes placed on either end of the minor axis in an elliptic nozzle.
References
More filters
Journal ArticleDOI
The use of fast Fourier transform for the estimation of power spectra: A method based on time averaging over short, modified periodograms
TL;DR: In this article, the use of the fast Fourier transform in power spectrum analysis is described, and the method involves sectioning the record and averaging modified periodograms of the sections.
Journal ArticleDOI
Dynamic mode decomposition of numerical and experimental data
TL;DR: In this article, a method is introduced that is able to extract dynamic information from flow fields that are either generated by a (direct) numerical simulation or visualized/measured in a physical experiment.
Journal ArticleDOI
Spectral analysis of nonlinear flows
TL;DR: In this article, a technique for describing the global behaviour of complex nonlinear flows by decomposing the flow into modes determined from spectral analysis of the Koopman operator, an infinite-dimensional linear operator associated with the full nonlinear system, is presented.
Journal Article
Spectral analysis of nonlinear flows
TL;DR: In this article, a technique for describing the global behaviour of complex nonlinear flows by decomposing the flow into modes determined from spectral analysis of the Koopman operator, an infinite-dimensional linear operator associated with the full nonlinear system, is presented.
Related Papers (5)
Screech tones from free and ducted supersonic jets
Experiments characterizing nonlinear shear layer dynamics in a supersonic rectangular jet undergoing screech
Steven H. Walker,Flint O. Thomas +1 more