Dispersion and upwind-side shear-layer characteristics of forward-inclined transverse jet in crossflow

Transverse jets in crossflow are widely used in energy systems, especially as dilution air jets, fuel/air mixers, and combustion equipment, and have received extensive attention and plenty of research. However, the studies of the circular transverse jet issued from a circular gap at the circumferential direction of a tube in crossflow are very limited. This paper studies a relatively new jet: the circular transverse jet. Firstly, numerical calculations are conducted under different turbulence models but with the same boundary conditions. By comparing the numerical results of different turbulence models with the existing experimental data, the turbulence model which is most suitable for the numerical calculation of the circular transverse jet is selected. Then, this turbulence model is used to calculate and analyze the flow field structure and its characteristics. It is found that due to the aerodynamic barrier effect of the high-velocity jet, a negative pressure zone is formed behind the jet trajectory; the existence of the negative pressure zone causes the formation of a vortex structure and a recirculation zone downstream the circular transverse jet; and the length/width ratio of the recirculation zone does not change with the changes of the crossflow and the jet parameters. It means that the recirculation zone is a fixed shape for a definite device. This would be fundamental references for the studying of fuel/air mixing characteristics and combustion efficiency when the circular transverse jet is used as a fuel/air mixer and stable combustion system.

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Spatial Development of Shear Layer Vortices in a Reacting Jet in Crossflow

2018 AIAA Aerospace Sciences Meeting ◽

10.2514/6.2018-2186 ◽

2018 ◽

Author(s):

Vedanth Nair ◽

Benjamin Wilde ◽

Benjamin L. Emerson ◽

Tim C. Lieuwen

Keyword(s):

Shear Layer ◽

Spatial Development ◽

Jet In Crossflow

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Transition to global instability in transverse-jet shear layers

Journal of Fluid Mechanics ◽

10.1017/s0022112010003046 ◽

2010 ◽

Vol 661 ◽

pp. 294-315 ◽

Cited By ~ 35

Author(s):

J. DAVITIAN ◽

D. GETSINGER ◽

C. HENDRICKSON ◽

A. R. KARAGOZIAN

Keyword(s):

Shear Layer ◽

Near Field ◽

Single Mode ◽

Shear Layers ◽

Global Instability ◽

Frequency Tracking ◽

Transverse Jet ◽

Critical Range ◽

Crossflow Velocity ◽

Lock In

In a recent paper (Megerianet al.,J. Fluid Mech., vol. 593, 2007, pp. 93–129), experimental exploration of the behaviour of transverse-jet near-field shear-layer instabilities suggests a significant change in the character of the instability as jet-to-crossflow velocity ratiosRare reduced below a critical range. The present study provides a detailed exploration of and additional insights into this transition, with quantification of the growth of disturbances at various locations along and about the jet shear layer, frequency tracking and response of the transverse jet to very strong single-mode forcing, creating a ‘lock-in’ response in the shear layer. In all instances, there is clear evidence that the flush transverse jet's near-field shear layer becomes globally unstable whenRlies at or below a critical range near 3. These findings have important implications for and provide the underlying strategy by which active control of the transverse jet may be developed.

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Strategic Control of Transverse Jet Shear Layer Instabilities

AIAA Journal ◽

10.2514/1.j050336 ◽

2010 ◽

Vol 48 (9) ◽

pp. 2145-2156 ◽

Cited By ~ 30

Author(s):

J. Davitian ◽

C. Hendrickson ◽

D. Getsinger ◽

R. T. M'Closkey ◽

A. R. Karagozian

Keyword(s):

Shear Layer ◽

Strategic Control ◽

Transverse Jet

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Evaluation of a Machine Learning Turbulence Model in a Square Transverse Jet in Crossflow

10.1115/1.0003116v ◽

2021 ◽

Author(s):

Ruben Bruno Diaz ◽

Fabiola Paula Costa ◽

Pedro M. Milani ◽

Jesuino Takachi Tomita ◽

Cleverson Bringhenti

Keyword(s):

Machine Learning ◽

Turbulence Model ◽

Transverse Jet ◽

Jet In Crossflow

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Transverse-jet shear-layer instabilities. Part 1. Experimental studies

Journal of Fluid Mechanics ◽

10.1017/s0022112007008385 ◽

2007 ◽

Vol 593 ◽

pp. 93-129 ◽

Cited By ~ 97

Author(s):

S. MEGERIAN ◽

J. DAVITIAN ◽

L. S. DE B. ALVES ◽

A. R. KARAGOZIAN

Keyword(s):

Shear Layer ◽

Near Field ◽

Experimental Studies ◽

Single Mode ◽

Tunnel Wall ◽

Low Level ◽

Transverse Jet ◽

Free Jet ◽

Instability Modes ◽

Crossflow Velocity

This study provides a detailed exploration of the near-field shear-layer instabilities associated with a gaseous jet injected normally into crossflow, also known as the transverse jet. Jet injection from nozzles which are flush as well as elevated with respect to the tunnel wall are explored experimentally in this study, for jet-to-crossflow velocity ratiosRin the range 1 ≲R≤ 10 and with jet Reynolds numbers of 2000 and 3000. The results indicate that the nature of the transverse jet instability is significantly different from that of the free jet, and that the instability changes in character as the crossflow velocity is increased. Dominant instability modes are observed to be strengthened, to move closer to the jet orifice, and to increase in frequency as crossflow velocity increases for the regime 3.5 <R≤ 10. The instabilities also exhibit mode shifting downstream along the jet shear layer for either nozzle configuration at these moderately high values ofR. WhenRis reduced below 3.5 in the flush injection experiments, single-mode instabilities are dramatically strengthened, forming almost immediately within the shear layer in addition to harmonic and subharmonic modes, without any evidence of mode shifting. Under these conditions, the dominant and initial mode frequencies tend to decrease with increasing crossflow. In contrast, the instabilities in the elevated jet experiments are weakened as R is reduced below about 4, probably owing to an increase in the vertical coflow magnitude exterior to the elevated nozzle, untilRfalls below 1.25, at which point the elevated jet instabilities become remarkably similar to those for the flush injected jet. Low-level jet forcing has no appreciable influence on the shear-layer response when these strong modes are present, in contrast to the significant influence of low-level forcing otherwise. These studies suggest profound differences in transverse-jet shear-layer instabilities, depending on the flow regime, and help to explain differences previously observed in transverse jets controlled by strong forcing.

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Transverse-jet shear-layer instabilities. Part 2. Linear analysis for large jet-to-crossflow velocity ratio

Journal of Fluid Mechanics ◽

10.1017/s002211200800102x ◽

2008 ◽

Vol 602 ◽

pp. 383-401 ◽

Cited By ~ 31

Author(s):

LEONARDO S. DE B. ALVES ◽

ROBERT E. KELLY ◽

ANN R. KARAGOZIAN

Keyword(s):

Shear Layer ◽

Near Field ◽

Velocity Ratio ◽

Base Flow ◽

Experimental Results ◽

Dimensional Parameter ◽

Potential Core ◽

Transverse Jet ◽

Spatial Growth ◽

Crossflow Velocity

The dominant non-dimensional parameter for isodensity transverse jet flow is the mean jet-to-crossflow velocity ratio,R. In Part 1 (Megerianet al.,J. Fluid Mech., vol. 593, 2007, p. 93), experimental results are presented for the behaviour of transverse-jet near-field shear-layer instabilities for velocity ratios in the range 1 <R≤ 10. A local linear stability analysis is presented in this paper for the subrangeR>4, using two different base flows for the transverse jet. The first analysis assumes the flow field to be described by a modified version of the potential flow solution of Coelho & Hunt (J. Fluid Mech., vol. 200, 1989, p. 95), in which the jet is enclosed by a vortex sheet. The second analysis assumes a continuous velocity model based on the same inviscid base flow; this analysis is valid for the larger values of Strouhal number expected to be typical of the most unstable disturbances, and allows prediction of a maximum spatial growth rate for the disturbances. In both approaches, results are obtained by expanding in inverse powers ofRso that the free-jet results are obtained asR→∞. The results from both approaches agree in the moderately low-frequency regime. Maximum spatial growth rates and associated Strouhal numbers extracted from the second approach both increase with decreasing velocity ratioR, in agreement with the experimental results from Part 1 in the range 4<R≤10. The nominally axisymmetric mode is found to be the most unstable mode in the transverse-jet shear-layer near-field region, upstream of the end of the potential core. The overall agreement of theoretical and experimental results suggests that convective instability occurs in the transverse-jet shear layer for jet-to-crossflow velocity ratios above 4, and that the instability is strengthened asRis decreased.

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