Proposed relationship between broadband shock associated noise and screech tones

Tam, Christopher K. W.; Seiner, J. M.; Yu, J. C.

doi:10.1016/s0022-460x(86)80212-7

Cited by 282 publications

(181 citation statements)

References 17 publications

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“…[6][7][8][9][10] The broadband contribution is also produced by the interaction of vortices with the shock cells but without feedback loop. [11][12][13] Although acoustically interesting and used in a large number of industrial sectors for discharging flow or generating pressure drops, acoustic radiation from a flow through a perforated plate or more generally from multiple jet nozzle has been very little studied in the literature. Among the few works on this subject, one can cite the work of Atvars et al 14 who studied the noise radiated by multitube nozzles and acoustically lined ejectors.…”

Section: Figure 1 Experimental Setup and Of Few Typical Samplesmentioning

confidence: 99%

Experimental investigation of the transient bleed valve noise

Laffay

Jacob

Moreau

et al. 2017

23rd AIAA/CEAS Aeroacoustics Conference

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This study presents the first step of an experimental study of the transient bleed valve noise. It was carried out on a simplified TBV geometry composed of a cylindrical inlet pipe leading to a diaphragm or a perforated disk for the purpose of generating pressure drops. Numerous diaphragms and grids have been tested in order to identify parameters that influence the acoustic radiation of the TBV and for NPR (Nozzle pressure ratio) from 1.2 to 3.6 to cover both subsonic and supersonic regimes. A large number of acoustic behaviors have been identified. For diaphragms far field acoustic spectra is dominated by mixing noise for all NPR and by shock-associated noise (screech and broadband shock associated noise (BBSAN)) when the critical value of the NPR delimiting the subsonic and supersonic behavior (NPRc = 1.89) is exceeded. For grids the mixing noise is still present but is composed of two humps. The parametric study allowed to associate the first hump to the noise of an equivalent jet having the smallest diameter encircling the grid perforations while the second is associated to the noise of the outer isolated jets. A first prediction model has thus been proposed based on this double source. Furthermore, the grids offer a significant noise reduction in the audible range with respect to a diaphragm of the same cross-section by shifting the radiation towards the high frequencies. The noise associated with supersonic phenomena (screech and BBSAN) are also strongly reduced and even suppressed in most of the tested cases.

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Section: Figure 1 Experimental Setup and Of Few Typical Samplesmentioning

confidence: 99%

Experimental investigation of the transient bleed valve noise

Laffay

Jacob

Moreau

et al. 2017

23rd AIAA/CEAS Aeroacoustics Conference

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show abstract

“…Correspondingly, an increase in peak BSAN frequency was achieved by all of the investigated chevron configurations. The theoretical relation of Tam et al [36] indicated that the trends in shock length reduction and BSAN peak frequency increase were captured using the mean shock length determination routine defined herein. Discrepancies in relative amplitude existed, most likely due to use of non-centerline velocity profiles, which introduced non-orthogonal length measurements because of jet spread.…”

Section: Discussionmentioning

confidence: 99%

“…6a. This observation angle was chosen as the fundamental screech tone primarily propagates upstream due to the weakest link in the aeroacoustic feedback mechanism occurring at the nozzle lip [36]. The BSAN peak frequency and amplitude were determined by curve-fitting a gamma distribution to the acoustic data acquired at Ψ¼90°.…”

Section: Acoustic Fieldmentioning

confidence: 99%

“…8. This relation was selected as it is an empirical extension of the work of Tam et al [36] (Eq. (1)), which includes the observed effect of instability modes on the screech frequency:…”

Section: Acoustic Fieldmentioning

confidence: 99%

“…The predominant feature of the results is a universal increase in peak frequency by the application of any chevron configuration. Considering the relation of Tam et al [36] (shown below in Eq. (2)) this can be explained by a reduction of the average shock cell spacing and/or an increase in the convective velocity, though previous studies [12,51,44] indicate that the reduction in the shock spacing alone can account for the frequency increase:…”

Section: Acoustic Fieldmentioning

confidence: 99%

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