Hypersonic Mixing Enhancement by Compression at a High Convective Mach Number

AIAA Journal ◽  
2004 ◽  
Vol 42 (4) ◽  
pp. 787-795 ◽  
Author(s):  
Bernard Parent ◽  
Jean P. Sislian
Keyword(s):  
Mach Number ◽  
Mixing Enhancement ◽  
Convective Mach Number

Mixing enhancement in supersonic shear layers. III - Effect of convective Mach number

1988 ◽  
Author(s):  
T. YOUNG ◽  
E. ORAN ◽  
J. BORIS ◽  
RAAFAT GUIRGUIS ◽  
F. GRINSTEIN
Keyword(s):  
Mach Number ◽  
Shear Layers ◽  
Mixing Enhancement ◽  
Supersonic Shear Layers ◽  
Convective Mach Number

Large-scale structure and entrainment in the supersonic mixing layer

1995 ◽  
Vol 284 ◽  
pp. 171-216 ◽  
Author(s):  
N. T. Clemens ◽  
M. G. Mungal
Keyword(s):  
Mach Number ◽  
High Speed ◽  
Large Scale ◽  
Mixture Fraction ◽  
Mixing Layer ◽  
Mie Scattering ◽  
Planar Laser ◽  
The Cross ◽  
Convective Mach Number ◽  
Stream Direction

Experiments were conducted in a two-stream planar mixing layer at convective Mach numbers,Mc, of 0.28, 0.42, 0.50, 0.62 and 0.79. Planar laser Mie scattering (PLMS) from a condensed alcohol fog and planar laser-induced fluorescence (PLIF) of nitric oxide were used for flow visualization in the side, plan and end views. The PLIF signals were also used to characterize the turbulent mixture fraction fluctuations.Visualizations using PLMS indicate a transition in the turbulent structure from quasi-two-dimensionality at low convective Mach number, to more random three-dimensionality for$M_c\geqslant 0.62$. A transition is also observed in the core and braid regions of the spanwise rollers as the convective Mach number increases from 0.28 to 0.62. A change in the entrainment mechanism with increasing compressibility is also indicated by signal intensity profiles and perspective views of the PLMS and PLIF images. These show that atMc= 0.28 the instantaneous mixture fraction field typically exhibits a gradient in the streamwise direction, but is more uniform in the cross-stream direction. AtMc= 0.62 and 0.79, however, the mixture fraction field is more streamwise uniform and with a gradient in the cross-stream direction. This change in the composition of the structures is indicative of different entrainment motions at the different compressibility conditions. The statistical results are consistent with the qualitative observations and suggest that compressibility acts to reduce the magnitude of the mixture fraction fluctuations, particularly on the high-speed edge of the layer.

Numerical Simulation of the Supersonic Planar Mixing Layer

2011 ◽  
Vol 347-353 ◽  
pp. 922-926
Author(s):  
Jin Liang Gu ◽  
Huan Hao Zhang ◽  
Zhi Hua Chen ◽  
Xiao Hai Jiang
Keyword(s):  
Numerical Simulation ◽  
Mach Number ◽  
Large Eddy Simulation ◽  
Engineering Design ◽  
Mixing Layer ◽  
Eddy Simulation ◽  
Layer Structures ◽  
Eddy Characteristics ◽  
Large Eddy ◽  
Convective Mach Number

Large eddy simulation (LES) has been used to simulate both non-reacting and reacting supersonic planar mixing layers at convective Mach number Mc=0.3. The different eddy characteristics of two cases have been visualized and discussed based on our calculated results, and the differences of mixing layer structures have also been shown, which can provide some important guide for future relative engineering design.

Entrainment in a compressible turbulent shear layer

2016 ◽  
Vol 797 ◽  
pp. 564-603 ◽  
Author(s):  
Reza Jahanbakhshi ◽  
Cyrus K. Madnia
Keyword(s):  
Mach Number ◽  
Shear Layer ◽  
Surface Area ◽  
Mass Flux ◽  
Geometrical Shape ◽  
Turbulent Region ◽  
Irrotational Flow ◽  
Entrainment Velocity ◽  
Mass Fluxes ◽  
Convective Mach Number

Direct numerical simulations (DNS) of temporally evolving shear layers have been performed to study the entrainment of irrotational flow into the turbulent region across the turbulent/non-turbulent interface (TNTI). Four cases with convective Mach number from 0.2 to 1.8 are used. Entrainment is studied via two mechanisms; nibbling, considered as vorticity diffusion across the TNTI, and engulfment, the drawing of the pockets of the outside irrotational fluid into the turbulent region. The mass flow rate due to nibbling is calculated as the product of the entrained mass flux with the surface area of the TNTI. It is found that increasing the convective Mach number results in a decrease of the average entrained mass flux and the surface area of the TNTI. For the incompressible shear layer the local entrained mass flux is shown to be highly correlated with the viscous terms. However, as the convective Mach number increases, the mass fluxes due to the baroclinic and the dilatation terms play a more important role in the local entrainment process. It is observed that the entrained mass flux is dependent on the local dilatation and geometrical shape of the TNTI. For a compressible shear layer, most of the entrainment of the irrotational flow into the turbulent region due to nibbling is associated with the compressed regions on the TNTI. As the convective Mach number increases, the percentage of the compressed regions on the TNTI decreases, resulting in a reduction of the average entrained mass flux. It is also shown that the local shape of the interface, looking from the turbulent region, is dominated by concave shaped surfaces with radii of curvature of the order of the Taylor length scale. The average entrained mass flux is found to be larger on highly curved concave shaped surfaces regardless of the level of dilatation. The mass fluxes due to vortex stretching, baroclinic torque and the shear stress/density gradient terms are weak functions of the local curvatures on the TNTI, whereas the mass fluxes due to dilatation and viscous diffusion plus the viscous dissipation terms have a stronger dependency on the local curvatures. As the convective Mach number increases, the probability of finding highly curved concave shaped surfaces on the TNTI decreases, whereas the probability of finding flatter concave and convex shaped surfaces increases. This results in a decrease of the average entrained mass flux across the TNTI. Similar to the previous works on jets, the results show that the contribution of the engulfment to the total entrainment is small for both incompressible and compressible mixing layers. It is also shown that increasing the convective Mach number decreases the velocities associated with the entrainment, i.e. induced velocity, boundary entrainment velocity and local entrainment velocity.

Experimental investigation on mixing characteristics of high speed co-flow jets by using tabbed chevron nozzle

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Saravanan A. R. ◽  
Thanigaiarasu S. ◽  
Rakesh Divvela ◽  
Rathakrishnan E.
Keyword(s):  
Experimental Investigation ◽  
Mach Number ◽  
High Speed ◽  
Radial Profile ◽  
Mixing Enhancement ◽  
Primary Flow ◽  
Potential Core ◽  
Mixing Characteristics ◽  
Chevron Nozzle ◽  
Better Than

Abstract The present study investigates the effect of chevron with tab (Tabbed chevron) fixed at the exit of the co-flowing primary nozzle on the mixing characteristics in subsonic and sonic jets. The experiment was conducted for the jet Mach number 0.6 and 0.8. The centerline Mach number decay was calculated for all these jet Mach numbers for the co-flow baseline nozzle, nozzle with chevrons and tabbed chevron (primary flow) nozzle respectively. It was found that tabbed chevron was effective in reducing the potential core length by 88.23% as compared to the chevron nozzle with baseline nozzle. The radial profile also shows that the mixing enhancement by tabbed chevron is better than chevron nozzle.

scholarly journals Effect of Strut Geometry in Supersonic Mixing

2020 ◽  
Vol 9 (6) ◽  
pp. 386-389
Keyword(s):  
Experimental Study ◽  
Mach Number ◽  
Residence Time ◽  
High Speed ◽  
Free Stream ◽  
Mixing Enhancement ◽  
Supersonic Mixing ◽  
Mixing Chamber ◽  
Mixing Method ◽  
Selection Of

Effective mixing in a short mixing chamber is a major challenge in supersonic air breathing engines, especially the mixing between two high speed co-axial streams. The residence time is a major factor to get the two streams properly mixed. The selection of mixing method is crucial in the supersonic conditions. An experimental study has been performed on the supersonic mixing of air from strut injectors of various combinations in their trailing ramp angles with a free stream air of Mach number 2. Two different configurations of geometries, a plain geometry and a lobed geometry considered and further two different combinations, slot and hole injections, are taken for the study in each geometry. Among different combinations, it is found that a better mixing enhancement is achieved for the 9o lobed geometry struts.

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