Flow field comparisons from three Navier-Stokes solvers for an axisymmetric separate flow jet

Koch, L. Danielle; Bridges, Jackie; Khavaran, Abbas

doi:10.2514/6.2002-672

Cited by 20 publications

(10 citation statements)

References 4 publications

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“…For example, Koch et. al [1] investigated subsonic axisymmetric separate flow jets with three flow solvers using twoequation k-turbulence models where the mixing rate in each of the calculations was slower than that indicated by experimental results. The turbulent kinetic energy levels were also lower, which corresponds to the slower mixing rate.…”

Section: Introductionmentioning

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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Section: Introductionmentioning

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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“…Since noise generation is an inherently unsteady process, LES will probably be the most powerful computational tool to be used in jet noise research in the foreseeable future since it is the only way, other than DNS, to obtain time-accurate unsteady data. Although the application of Reynolds Averaged Navier Stokes (RANS) methods to jet noise prediction is also a subject of ongoing research, [4][5][6][7][8] RANS methods heavily rely on turbulence models to model all relevant scales of turbulence. Moreover, such methods try to predict the noise using the mean flow properties provided by a RANS solver.…”

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confidence: 99%

Coupling of Integral Acoustics Methods with LES for Jet Noise Prediction

Uzun

Lyrintzis

Blaisdell

2004

42nd AIAA Aerospace Sciences Meeting and Exhibit

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This study is focused on developing a Computational Aeroacoustics (CAA) methodology that couples the near field unsteady flow field data computed by a 3-D Large Eddy Simulation (LES) code with various integral acoustic formulations for the far field noise prediction of turbulent jets. Noise computations performed for a Reynolds number 400,000 jet using various integral acoustic results are presented and the results are compared against each other as well with an experimental jet at similar flow conditions. Our results show that the surface integral acoustics methods (Kirchhoff and Ffowcs Williams -Hawkings) give similar results to the volume integral method (Lighthill's acoustic analogy) at a much lower cost. To our best knowledge, Lighthill's acoustic analogy was applied to a reasonably high Reynolds number jet for the first time in this study. A database greater than 1 Terabytes (TB) in size was post-processed using 1160 processors in parallel on a modern supercomputing platform for this purpose.

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“…The solid lines and symbols represent the numerical results and the experimental data presented in Ref. 32, respectively. The computed result is in very good agreement with the experimental data at the first streamwise station indicating that the early jet shear layers are quite well resolved in the simulation.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Ref. 32 found experimentally that the jet flow is a self-similar single stream at locations greater than about six fan diameters downstream of the fan nozzle exit plane, which corresponds to about x = 11 here. The numerical results are in general agreement with the experimental results for stations two, three, and five.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…The current computation is for a subsonic dual-stream flow issuing from the NASA Glenn 3BB baseline coannular nozzle, 32 see Fig. 1 In what follows, the exit diameter D of the of the core nozzle, the density ρ ∞ , the speed of sound a ∞ , and the (static) temperature T ∞ in the co-flow are used as scales to make all the dependent variables nondimensional.…”

Section: The Jet Flowmentioning

confidence: 99%

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