On sound radiation from sources in parallel sheared jet flows

Tester, Brian J.; Burrin, R. H.

doi:10.2514/6.1974-57

Cited by 11 publications

(4 citation statements)

References 12 publications

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“…The present study may be regarded as a simplified attempt to solve equations of the type derived by Lilley and Goldstein & Howes where, in the interest of obtaining closed-form solutions and motivated by the desire to avoid obscuring the physics by complicated numerical approaches, the jet flow is modelled as a simple, round, plug-flow jet. The reader's attention is also drawn to the work of Tester & Burrin (1974) and Berman (1974), who have expounded ideas very similar to those contained in the present study. The papers of Ribner (1960, Powell (1960) and Csanady (1 966) also deserve mention as having drawn attention to mean-flow shrouding effects.…”

Section: Introductionmentioning

confidence: 62%

The influence of jet flow on jet noise. Part 1. The noise of unheated jets

Mani¹

1976

J. Fluid Mech.

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The present paper and part 2 (adjacent) study the sound field produced by a convected point quadrupole embedded in and moving along the axis of a round plug-flow jet. Only subsonic eddy convection velocities are considered. We examine cold jets here and hot jets in part 2. A principal feature of the study is extensive comparison with jet-noise data. It appears that this simple model problem succeeds in explaining all the major interesting features of jet-noise data, on both hot and cold jets, for jet exit velocities in the low supersonic range. Particular success is achieved in explaining aspects of the data not explainable by the Lighthill acoustic-analogy approach. The picture of jet-noise generation that emerges (at least for jet velocities in the low supersonic regime) is in many respects a striking reaffirmation of the Lighthill point of view. It appears that there is an intrinsic or universal distribution of compact quadrupoles, whose strength and frequency distribution scale with the jet velocity and nozzle diameter as would be expected from simple dimensional reasoning, responsible for jet-noise generation. These quadrupoles are of course convected by the mean flow and satisfactory agreement with the data is obtained by assuming that they are devoid of any intrinsic directionality. There appears to be no significant jet Mach number (compressibility) or jet temperature effect on the scaling of this intrinsic distribution. The essential improvement over the Lighthill analysis is the incorporation of mean-flow shrouding effects on the radiation of the convected quadrupoles. It is perhaps no exaggeration to claim that, with the incorporation of such a shrouding effect, the problem of scaling jet noise with regard to the jet velocity, jet temperature, jet size and the angle from the jet axis appears to be completely resolved. (The ‘scaling’ principle cannot of course be very simply expressed and in fact needs calculations of the sort contained in the present paper to implement it.)

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Section: Introductionmentioning

confidence: 62%

The influence of jet flow on jet noise. Part 1. The noise of unheated jets

Mani¹

1976

J. Fluid Mech.

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“…Consider now the far field which would be generated by a compact quadrupole source of the form of equation (4). The directivity produced by low-frequency convecting point sources in jets has been computed using equation (2) with the source given by equation (4) (or something very similar) by Goldstein (1975Goldstein ( , 1976b, Tester & Morfey (1976), and Balsa (1977); solutions in the high-frequency limit are given by Tester & Burrin (1974), Balsa (1976Balsa ( , 1977, Tester & Morfey (1976), and Goldstein (1982) and others; full solutions are given for the special case of plug flow by Mani (1976). These computations are reviewed by Goldstein (1984).…”

Section: The Structure Of the Source Terms And Their Asymptotic Far-fmentioning

confidence: 99%

Sound generation in a mixing layer

1997

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The sound generated by vortex pairing in a two-dimensional compressible mixing layer is investigated. Direct numerical simulations (DNS) of the Navier–Stokes equations are used to compute both the near-field region and a portion of the acoustic field. The acoustic analogy due to Lilley (1974) is also solved with acoustic sources determined from the near-field data of the DNS. It is shown that several commonly made simplifications to the acoustic sources can lead to erroneous predictions for the acoustic field. Predictions based on the quadrupole form of the source terms derived by Goldstein (1976a, 1984) are in excellent agreement with the acoustic field from the DNS. However, despite the low Mach number of the flow, the acoustic far field generated by the vortex pairings cannot be described by considering compact quadrupole sources. The acoustic sources have the form of modulated wave packets and the acoustic far field is described by a superdirective model (Crighton & Huerre 1990). The presence of flow–acoustic interactions in the computed source terms causes the acoustic field predicted by the acoustic analogy to be very sensitive to small changes in the description of the source.

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“…This invites novel analysis approaches and manipulations, which can lead to a deeper understanding of mechanisms of noise generated by turbulence and, ultimately, to a successful solution of practical problems. In the present study of added sources we do not present extensive comparisons with experimental data (e.g., Atvars et al [10], Tester and Burrin [11], Ahuja et al [12]), primarily because most of that data was at lower Mach numbers and Strouhal numbers than we focused on; this is acceptable since the level of confidence in LES is now high, within the well-known limitations. Our study for the most part only involves simulations and theory, where the theory does not address the effects of turbulence, so that close agreement was not expected at first.…”

Section: Introductionmentioning

confidence: 95%

Added Sound Sources in Jets; Theory and Simulation

Spalart

Shur

Strelets

2009

International Journal of Aeroacoustics

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The Large-Eddy Simulation (LES) system established over the last six years is reviewed in terms of its progress in accuracy and transition physics, and is then used to explore the transmission of noise from a known local source through a turbulent region, here the shear layer of a jet. For this, weak artificial monopole sources are added to an LES, and their sound tracked in detail both in the near-field and far-field. Sources are placed in the potential cores of the primary and secondary streams, as well as in the mixing layer and outside the jet with various locations relative to the observer, and different frequencies. Simple Ray Acoustics theory based on the mean flow field and assuming full conservation of wave action via the Blokhintsev equation is quite successful, both in terms of wave-fronts and sound level, even at a diameter Strouhal number St of only 0.5. The principal difference is that LES predicts a gradual cone of silence upstream, which theory does not. The abrupt downstream cones of silence agree. Thus, even crossing a mixing layer with a Mach 0.9 difference does not appear to alter the sound much. Cases with a dual nozzle and hot core stream return similar findings. This will be helpful when creating lower-order prediction tools, and correcting noise measurements made outside a co-flow.

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On sound radiation from sources in parallel sheared jet flows

Cited by 11 publications

References 12 publications

The influence of jet flow on jet noise. Part 1. The noise of unheated jets

The influence of jet flow on jet noise. Part 1. The noise of unheated jets

Sound generation in a mixing layer

Added Sound Sources in Jets; Theory and Simulation

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