Numerical Prediction of Chevron Nozzle Noise Reduction Using Wind-MGBK Methodology

Engblom, William; Bridges, Jackie; Khavarant, A.

doi:10.2514/6.2004-2979

Cited by 53 publications

(34 citation statements)

References 11 publications

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“…Similar deviations are also found in round jet case SMC000. Such discrepancy seems to be common in jet simulations by RANS [19,20] because the RANS model cannot simulate the vortex stretching term well [21]. Nevertheless, the present results match well with RANS solutions of Engel et al [15].…”

Section: Description Of the Baseflowsupporting

confidence: 78%

Instability waves and low-frequency noise radiation in the subsonic chevron jet

Ran

Wan

et al. 2017

Acta Mech. Sin.

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Spatial instability waves associated with lowfrequency noise radiation at shallow polar angles in the chevron jet are investigated and are compared to the round counterpart. The Reynolds-averaged Navier-Stokes equations are solved to obtain the mean flow fields, which serve as the baseflow for linear stability analysis. The chevron jet has more complicated instability waves than the round jet, where three types of instability modes are identified in the vicinity of the nozzle, corresponding to radial shear, azimuthal shear, and their integrated effect of the baseflow, respectively. The most unstable frequency of all chevron modes and round modes in both jets decrease as the axial location moves downstream. Besides, the azimuthal shear effect related modes are more unstable than radial shear effect related modes at low frequencies. Compared to a round jet, a chevron jet reduces the growth rate of the most unstable modes at downstream locations. Moreover, linearized Euler equations are employed to obtain the beam pattern of pressure generated by spatially evolving instability waves at a dominant low frequency St = 0.3, and the acoustic efficiencies of these linear wavepackets are evaluated for both jets. It is found that the acoustic efficiency of linear wavepacket is able to be reduced greatly in the chevron jet, compared to the round jet.

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Section: Description Of the Baseflowsupporting

confidence: 78%

Instability waves and low-frequency noise radiation in the subsonic chevron jet

Ran

Wan

et al. 2017

Acta Mech. Sin.

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“…Engblom et. al [2] investigated a series of cold and hot single flow subsonic nozzle flows including a baseline round nozzle and several chevron nozzles, and a similar trend in the computations indicated much slower mixing towards the nozzle centerline than observed in experiments. Georgiadis et.…”

mentioning

confidence: 99%

“…Additionally, far downstream of the end of the jet potential core, it has been generally found that computed farfield mixing rate becomes too high. As a result, currently available RANS turbulence models are not adequate for accurate prediction of jet flow details.The impetus for the current investigation comes from detailed comparisons of the mean velocity and k fields predicted by the Wind code against Particle Imaging Velocimetry (PIV) data [2] that suggest that the RANS deficiency is most evident in the vicinity of the end of the potential core. More specifically, RANS predicts the shear layer to remain well-defined even as it reaches the centerline at a shallow angle, leaving a relatively thin "sliver" of core flow; whereas experimental results indicate that the shear layer is strongly diffused at the end of the potential core.…”

mentioning

confidence: 99%

Investigation of Variable-Diffusion Turbulence Model Correction for Round Jets

Engblom

Georgiadis

Khavaran³

et al. 2005

11th AIAA/CEAS Aeroacoustics Conference

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A Reynolds-Averaged Navier-Stokes (RANS) correction is described to account for a key effect of acoustic interaction near the end of the potential core for axisymmetric jets. Specifically, the Variable-Diffusion (Var-D) correction is formulated to mimic the effect of increased shear layer instability/motion near the end of the potential core by adjusting the local diffusion of k and . The proposed Var-D correction is initially evaluated for an unheated axisymmetric jet with a perfectly expanded jet Mach number of 0.5. Results for centerline velocity distribution and turbulent kinetic energy contours using commonly employed turbulence models (i.e. SST and k-) and k-with the Var-D correction are compared. Substantial improvement for prediction of potential core length, centerline velocity decay, and k field is demonstrated with the Var-D correction. The sensitivity of the proposed model to the closure coefficients associated with the correction is also examined using this cold subsonic jet case. Similar turbulence model performance comparisons are made for three other jets to evaluate the sensitivity of the correction to increased jet exhaust compressibility and heated jet flow conditions. The effect of the improved mean and turbulence field predictions obtained using the Var-D correction on farfield noise prediction is also evaluated using the JeNo acoustic analogy code, and shown to be negligible. Although the approach holds promise, the applicability of the Var-D correction is currently limited to round jets. I. Nomenclature= decay rate exponent = diffusion factor limit = dissipation of turbulent kinetic energy k = turbulent kinetic energy II. IntroductionDespite the routine use Reynolds-averaged Navier-Stokes (RANS) techniques for analysis of aerospace systems, the accurate prediction of nozzle and jet flows remains an area of needed improvement. Turbulence modeling remains the pacing item limiting the accuracy of jet flow predictions. Further, for aeroacoustics analysis, both the mean flow and turbulence state are important for assessment of noise emitted by jets under consideration. While Large-Eddy Simulation (LES) offers promise for the future by resolving the large-scale unsteady turbulent motion, this technique is currently prohibitively expensive computationally for realistic, high Reynolds number flows. Hence, RANS approaches will be required for the foreseeable future. As a result, there is still a need for work in the area of RANS turbulence modeling for jets, including turbulence model development to more accurately calculate developing jet flow features, as well as for comprehensive assessment of modeling advances to determine capabilities and limitations.Effective use of RANS computational fluid dynamics (CFD) in nozzle aeroacoustics investigations requires accurate simulation of both the mean flow and turbulent kinetic energy fields. Capturing the initial jet growth region remains a difficulty. There are many examples of subsonic jet potential core length underprediction in the literature. For ...

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“…In the past, this was accomplished using lobed mixer nozzles. More recently, the addition of chevrons [1][2][3][4][5][6][7][8][9] has been examined and found to reduce noise by up to 2.5 EPNdB during installed testing. However, while nozzles with chevrons can significantly reduce low frequency noise, they do so at the expense of increasing high frequency noise.…”

Section: Introductionmentioning

confidence: 99%

Computational Analyses of Offset-Stream Nozzles for Noise Reduction

Dippold

Foster

Wiese

2009

Journal of Propulsion and Power

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The Wind computational fluid dynamics code was used to perform a series of simulations on two offset stream nozzle concepts for jet noise reduction. The first concept used an S-duct to direct the secondary stream to the lower side of the nozzle. = nozzle plenum total temperature u = local axial velocity ujet = mass-averaged axial velocity of primary jet x, y, z = coordinate system ( ) = used to denote difference in discharge or thrust coefficient of the current configuration from the baseline configuration

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Numerical Prediction of Chevron Nozzle Noise Reduction Using Wind-MGBK Methodology

Cited by 53 publications

References 11 publications

Instability waves and low-frequency noise radiation in the subsonic chevron jet

Instability waves and low-frequency noise radiation in the subsonic chevron jet

Investigation of Variable-Diffusion Turbulence Model Correction for Round Jets

Computational Analyses of Offset-Stream Nozzles for Noise Reduction

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