Journal ArticleDOI
On the sound sources of screech tones radiated from choked circular jets.
Yoshikuni Umeda,Ryuji Ishii +1 more
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TLDR
It is shown that the speed of amoving sound source is supersonic and that the Mach cone generated by the moving sound source forms the helical-shaped wave front of the screech tone for the helicals oscillation mode of the jet.Abstract:
The generation mechanism of the screech tone in the helical oscillation mode is mainly investigated using a series of instantaneous schlieren photographs. From the photographs, five evanescent sound sources are observed as prominent points along the jet axis. The sound source for the dominant helical oscillation mode is found to be the second prominent point which moves along a circular orbit in a plane perpendicular to the jet axis and just downstream of the rear edge of the third shock cell. It is shown that the speed of a moving sound source is supersonic and that the Mach cone generated by the moving sound source forms the helical-shaped wave front of the screech tone for the helical oscillation mode of the jet. This idea of the moving sound source is well supported by a measured directionality of the screech tone. Sound sources of the other oscillation modes appearing in the other pressure ratio ranges are also described.read more
Citations
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Journal ArticleDOI
Aeroacoustic resonance and self-excitation in screeching and impinging supersonic jets – A review:
TL;DR: In this paper, the signature of an aeroacoustic resonance loop established by a shock-containing jet is described, and the resonance loop can be used to identify the origin of high-intensity, discrete-frequency acoustic tones.
Journal ArticleDOI
Coherent structure and sound production in the helical mode of a screeching axisymmetric jet
TL;DR: In this paper, the structure of a screeching axisymmetric jet in the helical C mode at a nozzle pressure ratio of 3.4 issuing from a convergent nozzle is studied using high-resolution particle image velocimetry.
Journal ArticleDOI
Large-Eddy Simulations of a Supersonic Jet and Its Near-Field Acoustic Properties
TL;DR: In this paper, large-eddy simulations of imperfectly expanded jet flows from a convergent-divergent nozzle with a sharp contraction at the nozzle throat have been carried out, and the flowfield and near-field acoustics for various total pressure ratios from overexpanded to underexpanded jet flow conditions have been investigated.
Journal ArticleDOI
Experimental characterisation of the screech feedback loop in underexpanded round jets
TL;DR: In this article, near-field acoustic measurements and time-resolved schlieren visualisations are performed on 10 round jets with the aim of analysing the different parts of the feedback loop related to the screech phenomenon in a systematic fashion.
Journal ArticleDOI
Harmonics of Jet Screech Tones
TL;DR: In this paper, the authors investigated the generation mechanism of the screech harmonics of imperfectly expanded supersonic jets undergoing strong screech emit not only the fundamental screech tone but also multiple tones at the harmonics at the fundamental frequency.
References
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Journal ArticleDOI
On the Mechanism of Choked Jet Noise
TL;DR: In this paper, the authors examined the noise in two-dimensional flow with the aid of a dynamic Schlieren apparatus, verifying the suggested mechanism and showing the similarity to axially symmetric flow where discontinuities in frequency, partly analogous to edge tones, occur.
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Proposed relationship between broadband shock associated noise and screech tones
TL;DR: In this paper, the relationship between broadband shock associated noise and screech tones is examined and it is shown that from the spectral characteristics point of view, the screech tone may be regarded as a special case of broadband wave associated noise.
Journal ArticleDOI
Supersonic Jet Screech: Half-century from Powell to the Present
TL;DR: A detailed overview of the state of the art in the field of supersonic jet screech can be found in this paper, including a historical perspective, a summary of recent developments and a critical assessment of the current state-of-the-art.
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Screech suppression in supersonic jets
TL;DR: In this paper, the authors investigated the effect of modifications to the nozzle exit on the fundamental screech tone of a jet operating under underexpanded sonic nozzles, and found that a large reduction of the screech amplitude can be obtained from modifications, although the extent of this suppression is mode dependent.
Journal ArticleDOI
On the Noise Emanating from a Two-Dimensional Jet Above the Critical Pressure
TL;DR: In this paper, an elementary theory based upon the hypothesis that the acoustic energy originates from the interaction of the stream disturbances with the shock waves of the flow, and connecting the stream disturbance with the radiated sound, is suggested.