Progress Toward Improving Jet Noise Predictions in Hot Jets

Khavaran, Abbas; Kenzakowski, D. C.

doi:10.2514/6.2007-12

Cited by 13 publications

(17 citation statements)

References 14 publications

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“…Comparisons were made with available PIV data collected at the Small Hot Jet Acoustic Rig (SHJAR) facility [6,28] at Glenn Research Center. Sample results that compares energy variance model with the total enthalpy variance model were presented in a previous study [29]. Specifically, a noticeable static temperature variance appears within the jet shear layer for unheated conditions at high exhaust speeds, compared to a practically insignificant total temperature variance.…”

Section: Subsonic Flowfield Simulationsmentioning

confidence: 84%

“…Nozzle flow boundary conditions were prescribed uniformly as inflow stagnation conditions for pressure and temperature imposed well upstream of the nozzle exit. Solution grid resolution sensitivity and convergence criteria were discussed in [29]. The same reference also compares fluctuations in total and static temperatures and shows that the former remains consistently small in unheated jets while the latter could grow to become significant with jet speed.…”

Section: Subsonic Flowfield Simulationsmentioning

confidence: 99%

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Hot Jets and Sources of Jet Noise

Khavaran

Kenzakowski

Mielke-Fagan

2010

International Journal of Aeroacoustics

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A prediction method based on the generalized acoustic analogy is presented and used to evaluate aerodynamic noise radiated from high-speed hot jets. The set of Euler equations are divided into two sets of equations that govern what may be considered as a non-radiating base flow plus its residual components. Under certain conditions, the residual equations are rearranged to form a wave equation. This equation consists of a third-order wave operator, plus a number of non-linear terms that are regarded as the equivalent sources of sound and their statistical characteristics are modeled. A specialized RANS solver provides the base flow as well as the variance in both velocity and thermal fluctuations that determine the source strength. The main objective here is to evaluate the relative contribution from various source components to the far-field spectra and to show the significance of temperature fluctuations as a potential source of aerodynamic noise in hot jets.

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Section: Subsonic Flowfield Simulationsmentioning

confidence: 84%

Section: Subsonic Flowfield Simulationsmentioning

confidence: 99%

Hot Jets and Sources of Jet Noise

Khavaran

Kenzakowski

Mielke-Fagan

2010

International Journal of Aeroacoustics

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“…But Goldstein and Leib (2008) found that it actually makes a significant contribution to the 90°sound field when the turbulence is assumed to be quasi-normal and axysymmetric and this probably remains true even when it is not quasi-normal. It is now generally believed that the remaining enthalpy term is an important sound source in heated jets and significant effort is underway to develop appropriate models for this quantity (Khavaran and Kenzakowski, 2007 where the summation convention is now being used for the Greek as well as the Latin indices. The non-linear dependent variable p e (or equivalently p e -p 0 ) causes no particular difficulty here because it reduces to the ordinary pressure fluctuation p -p 0 in the far field where the sound is to be calculated.…”

Section: Lilley's Modification Of Lighthill's Equationmentioning

confidence: 99%

“…unheated) jets at O(1) Mach numbers-which means that e′ 4i will then be negligible compared to e′ ji and that the source term can, therefore, be considerably simplified. But recent RANS computotions (Khavaran and Kenzakowski, 2007) suggest that it may be the fixed frame residual stagnation enthalpy h′ s +v % i v′ i that is negligibly small compared to v′ i in cold (i.e. unheated) jets at very high Mach numbers.…”

Section: A Generalized Approachmentioning

confidence: 99%

Relation between the Generalized Acoustic Analogy and Lilley's Contributions to Aeroacoustics

Goldstein

2010

International Journal of Aeroacoustics

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This paper reviews Lilley's reformulation of Lighthill's equation and shows that it can be obtained as a special case of a much more general acoustic analogy. It also shows how this generalized analogy can be used to eliminate some of the difficulties that arise when more conventional parallel flow analogies are applied to high speed jets. And, finally, some recent applications of these ideas are discussed.

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“…But this would require modeling many cross-coupling terms that would be difficult to estimate from any standard RANS based code. It may, however, be possible to do this by extending a RANS code to yield information about the RMS temperature fluctuations (as was done by Khavaran and Kenzakowski, 2007) if the velocity and sound speed fluctuations are assumed to be uncorrelated in the sense that ( )…”

Section: ( )mentioning

confidence: 99%

The aeroacoustics of slowly diverging supersonic jets

2008

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This paper is concerned with utilizing the acoustic analogy approach to predict the sound from unheated supersonic jets. Previous attempts have been unsuccessful at making such predictions over the Mach number range of practical interest. The present paper, therefore, focuses on implementing the necessary refinements needed to accomplish this objective. The important effects influencing peak supersonic noise turn out to be source convection, mean flow refraction, mean flow amplification, and source non-compactness. It appears that the last two effects have not been adequately dealt with in the literature. The first of these because the usual parallel flow models produce most of the amplification in the so called critical layer where the solution becomes singular and, therefore, causes the predicted sound field to become infinite as well. We deal with this by introducing a new weakly non parallel flow analysis that eliminates the critical layer singularity. This has a strong effect on the shape of the peak noise spectrum. The last effect places severe demands on the source models at the higher Mach numbers because the retarded time variations significantly increase the sensitivity of the radiated sound to the source structure in this case. A highly refined (non-separable) source model is, therefore, introduced in this paper.

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Progress Toward Improving Jet Noise Predictions in Hot Jets

Cited by 13 publications

References 14 publications

Hot Jets and Sources of Jet Noise

Hot Jets and Sources of Jet Noise

Relation between the Generalized Acoustic Analogy and Lilley's Contributions to Aeroacoustics

The aeroacoustics of slowly diverging supersonic jets

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