Dual stream axisymmetric mixing in the presence of axial vorticity

Belovich, Vincent; Samimy, Mo; Reeder, Mark F.

doi:10.2514/6.1994-3084

Cited by 7 publications

(10 citation statements)

References 2 publications

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“…Flow instabilities in plane wakes and shear layers have been studied for a lobed mixer type geometry with small lobe ramp angles (␣Ͻ1°) and moderate Reynolds numbers; 22,23 an uncoupled development of streamwise and spanwise vorticity by the lobed trailing edge is seen here. Axisymmetric lobed or corrugated mixer geometries have also been investigated; 24,25 these also demonstrate the propensity for streamwise vorticity generation.…”

Section: Introductionmentioning

confidence: 99%

Mixing enhancement in a lobed injector

et al. 1997

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A study on a lobed jet mixing flow by using stereoscopic particle image velocimetry technique An experimental investigation of the non-reactive mixing processes associated with a lobed fuel injector in a coflowing air stream is presented. The lobed fuel injector is a device which generates streamwise vorticity, producing high strain rates which can enhance the mixing of reactants while delaying ignition in a controlled manner. The lobed injectors examined in the present study consist of two corrugated plates between which a fuel surrogate, CO 2 , is injected into coflowing air. Acetone is seeded in the CO 2 supply as a fuel marker. Comparison of two alternative lobed injector geometries is made with a straight fuel injector to determine net differences in mixing and strain fields due to streamwise vorticity generation. Planar laser-induced fluorescence ͑PLIF͒ of the seeded acetone yields two-dimensional images of the scalar concentration field at various downstream locations, from which local mixing and scalar dissipation rates are computed. It is found that the lobed injector geometry can enhance molecular mixing and create a highly strained flowfield, and that the strain rates generated by scalar energy dissipation can potentially delay ignition in a reacting flowfield.

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Section: Introductionmentioning

confidence: 99%

Mixing enhancement in a lobed injector

et al. 1997

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“…Similarly, the production term P k and the dissipation 1 appearing in the source terms of the k -1 equations are computed in the corresponding control volumes using equations (27) and (28). For the dissipation equation, 1 is explicitly specified at the grid nodes associated with near-wall control volumes according to equation (28), amounting to a Dirichlet boundary condition for the 1 equation.…”

Section: Numerical Discretizationmentioning

confidence: 99%

Prediction of a non-isothermal three-dimensional mixing layer created by a scarfed lobed mixer

Salman

McGuirk

Page

2006

Proceedings of the Institution of Mechanical Engineers, Part G:

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• This is an article from the journal, Proceedings of the Institution of Me- Abstract: The work presented here considers the complex mixing processes associated with a three-dimensional non-isothermal convoluted mixing layer such as produced by scarfed lobed mixers as used in aero-engine gas turbine exhaust ducts. Numerical simulations of the compressible Navier -Stokes equations in Reynolds-averaged form with a k -1 turbulence model are conducted. The discretization of the high-Reynolds-number form of the k-1 model for the unstructured mesh numerical solver used is described. The discretization was verified against two elemental flows that represent subcomponents of lobed mixer problems: a planar shear layer and a developing boundary layer. A grid dependency study is also presented for different grid types: purely quadrilateral, a purely triangular, and a mixed grid, to assess the influence of different mesh types on predictions. Results for a two-dimensional planar shear layer flow indicated that quadrilateral grids yielded best results for a given grid resolution. This result was confirmed in the numerical simulations of three-dimensional convoluted shear layers created by a generic lobed mixer geometry in which hexahedral grids yielded the most accurate results relative to a purely tetrahedral grid and a mixed grid. The model was finally used to simulate the flow field in an engine-representative scarfed mixer configuration under non-isothermal flow conditions representative of current engine practice. Results showed that the scarfed mixer introduced strong flow asymmetries in the azimuthal direction. This caused adjacent vortical structures produced by the alternating short and long gullies of the lobes to interact with one another and this behaviour dominated the flow evolution. Detailed comparisons between predicted and measured temperature fields were also carried out and generally showed encouraging agreement and capture of correct trends. The evolution of the predicted thermal mixing layer slightly lagged the measured data as was also the case for the velocity fields, indicating that improvements in the prediction of the thermal mixing layer may be strongly dependent on correct prediction of the momentum transport process as well as improved modelling of the turbulent heat fluxes.

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“…The results revealed the existence of large-scale streamwise vortices which Manning 21 reported the separate role of the streamwise vortices and the increased interfacial area on mixing; they also reported that the mixing enhancements of the lobed mixers increased with bypass ratio. Following Manning's work, Belovich et al 22 performed flow visualizations using a smoke test and found that the ratio of the mixing enhancement due to streamwise vorticity and that due to increased interfacial contact area increased with the doublestream velocity ratio. Elliot et al 23 reported three primary contributors to the mixing process in lobed mixing flows, namely spanwise vortices due to the Kelvin-Helmholtz instability, and increased interfacial contact area due to the trailing edge shape.…”

Section: Introductionmentioning

confidence: 99%

Aeroacoustic study of Internal Mixing Nozzles with Forced Lobed Mixers using a High-Mach Subsonic Lattice Boltzmann Scheme

Habibi

Mongeau

Casalino³

et al. 2014

20th AIAA/CEAS Aeroacoustics Conference

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Numerical simulation of the transient compressible flow through lobed mixers inside turbofan engine nozzles was performed. A novel entropic Lattice Boltzmann (LB) scheme was used for the computational studies. The very large eddy simulation scheme (LBM-VLES) was used to capture sub-grid scale flow structures. The sound generation process was investigated using the porous Ffwocs William-Hawkings (FW-H) surface integral method. A contoured dual-stream nozzle with a standard 12-lobed mixer (12CL) was selected as a test case to validate the LBM simulation. A detailed model of the mixer and the nozzle was concurrently created to simulate both the internal flow through the mixer and the external jet plume. All operating boundary conditions were imposed based on available measured data for the same mixer geometry. The transient and mean flow characteristics of the flow field were obtained both inside the nozzle and within the jet plume. The transient behavior of the streamwise vortices at the nozzle exit was visualized and quantified. The Reynolds number based on nozzle exit diameter was 2.02×10 6 and the acoustic Mach number reached 0.94. Both near field and far field results and trends were in good agreement with experimental data. Specifically the predicted averaged velocity field was within the range of measure values. The overall radiated sound pressure was within 2-3dB of measured sound at all directional angles.Nomenclature c i = particle velocity f = particle distribution function f i eq = equilibrium distribution function D J = jet diameter M = Mach number (M=U /a) P = pressure P a = ambient pressure Re D = jet Reynolds number (Re D = U j D j / υ j ) T = temperature T a = ambient temperature t = time * Corresponding Author, Research assistant -AIAA member, Email: kaveh.habibi@mail.mcgill.ca. † Professor, Senior AIAA member ‡ Technical director, AIAA member § Senior physics validation Engineer, AIAA member Downloaded by ROKETSAN MISSLES INC. on February 8, 2015 | http://arc.aiaa.org |

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Dual stream axisymmetric mixing in the presence of axial vorticity

Cited by 7 publications

References 2 publications

Mixing enhancement in a lobed injector

Mixing enhancement in a lobed injector

Prediction of a non-isothermal three-dimensional mixing layer created by a scarfed lobed mixer

Aeroacoustic study of Internal Mixing Nozzles with Forced Lobed Mixers using a High-Mach Subsonic Lattice Boltzmann Scheme

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