On the effect of a co-flowing stream on the structure of an axisymmetric turbulent jet

Borean, J.-L.; Huilier, Daniel; Burnage, H.

doi:10.1016/s0894-1777(97)10044-9

Cited by 12 publications

(7 citation statements)

References 14 publications

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“…[3][4][5][6] The effect of confinement and co-flowing streams (external mean velocity) on the structure of axisymmetric turbulent jets has also been studied. Borean et al 8 observed that the variation of the mean velocity and the rate of expansion of the jet are identical to that of a free jet, which suggests that the inner flow (jet) is not affected by the external flow. A similar result was obtained for the turbulent quantities where only some of the third order moments exhibit a different behavior near the axis of the flow.…”

Section: Introductionmentioning

confidence: 98%

Measurements and Modeling of the Flow Field in an Ultra-Low Emissions Combustor

Gopalakrishnan

Undapalli

Bobba

et al. 2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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The flowfield of a novel combustor design that can operate stably even at high flowrates and very lean conditions is studied. This Stagnation Point Reverse Flow (SPRF) combustor consists of a central injector at the single open end of a cylindrical chamber, with the injector inlet area much less than the open area of the combustor through which the exhaust products leave. Thus the flowfield can be characterized as a confined jet in an opposed flow. Experiments with Particle Image Velocimetry (PIV) as well as computations employing Large Eddy Simulations (LES) have been used to characterize the nonreacting and reacting flowfields within the combustor for premixed and nonpremixed modes of operation. Both nonreacting and reacting cases exhibit a "stagnation" region with local average and high fluctuating velocities. The reacting flows exhibit higher mean and fluctuating velocities than the nonreacting flow. The nonreacting flow stagnates earlier than the reacting flow due to the effects of gas expansion in the reacting flow case. Consequently, the jet decay rates are higher for the reacting flows. The high shear between the forward and reverse flows causes significant recirculation, resulting in enhanced entrainment and mixing of the returning hot product gases into the incoming reactant jet. Comparison of the instantaneous flowfields reveals that the reacting jets exhibit significant lateral motion and distortion compared to the nonreacting case. This parallels the large increase in fluctuating velocities and turbulence intensities that coincide witht the region of high heat release. Nonpremixed and premixed reacting flowfields at the same fuel and air mass flow rates are found to be very similar except in the near field region of the jet, due partly to the lack of heat release there in the nonpremixed case.

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Section: Introductionmentioning

confidence: 98%

Measurements and Modeling of the Flow Field in an Ultra-Low Emissions Combustor

Gopalakrishnan

Undapalli

Bobba

et al. 2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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“…Fewer studies presented the effect of confinements imposed peripherally at the jet flow. A parametric computational study was presented by Kandakure et al (2008), who focused on the effect of the enclosure size around a round jet that evolve inside a cylinder while Borean et al (1998) discussed the influence of the confinement combined with a co-flowing stream inside a cylindrical pipe. Both these studies mentioned the strong degradation of the entrainment process, which results to narrower radial extent of the jet and also the lower values of the turbulent statistics compared to those of typical "free" jets.…”

Section: Introductionmentioning

confidence: 99%

Influence of an Exit Wall Boundary on the Flow of a Circular Jet

2013

JAFM

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The flow of the axisymmetric jet constitutes a subject of research from the origins of fluid dynamics; however it remains a subject of interest due to the recent findings that denote the influence of flow and geometry conditions in configurations that diverge from the theoretical "free-jet" case. In the present study, the effect of a wall boundary produced by a circular disk of twice the jet diameter, which is imposed on the exit of the jet is investigated experimentally and numerically. Computational simulations are performed to predict the flow characteristics incorporating different turbulence models (k-ε and Reynolds Stress) and solvers (Simplec and Coupled). Supportive pressure measurements are used to evaluate the predictions within the initial region of a circular jet at two Reynolds numbers (50,000 and 65,000). The results indicate that the presence of the exit wall boundary results to the formation of recirculation zone behind the exit, which prevents the entrainment of ambient fluid. Comparing with the flow field of the free from confinement jet, it is shown that the imposition of the wall has a minor effect on the mean velocity field; it is however capable of altering the turbulent flow properties, including the normal and the Reynolds shear stresses, in the region before the establishment of the self-similarity zone.

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“…In this numerical study, several traditional scalar dissipation rate models are examined for scalar transport modeling in mixing turbulent round jets with co-flowing air. Therefore, it is not intended here to review previous work detail [9][10][11] on a co-flowing jet, since a review on the subject matter is given by the references [7,8]. The experimental and numerical investigations of this type of flow are also relatively scarce.…”

Section: Introductionmentioning

confidence: 99%

The dynamic field in turbulent round jet discharging into a co-flowing stream

Gazzah¹,

Boughattas²,

Belmabrouk³

et al. 2010

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The effects of a co-flow on a spreading and entrainment rate of turbulent round jets have been studied numerically. The first and second order closure models are used and have been compared with existing experimental data. The influence of theses models on the dynamic fields is examined. The results of the models in general agree well with the trends observed experimenttally. The co-flowing imposed noticeable restrictions on the spreading and the turbulent mixing. Finally, an entrainment hypothesis has been introduced to describe the development of turbulent jets issuing into a stagnant or co-flowing air. It relates the mass flow rate of the surrounding fluid entrained into the jet to the characteristic velocity difference between the jet and the co-flow. It is obvious that the co-flow decreases considerably the entrainment of air.

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On the effect of a co-flowing stream on the structure of an axisymmetric turbulent jet

Cited by 12 publications

References 14 publications

Measurements and Modeling of the Flow Field in an Ultra-Low Emissions Combustor

Measurements and Modeling of the Flow Field in an Ultra-Low Emissions Combustor

Influence of an Exit Wall Boundary on the Flow of a Circular Jet

The dynamic field in turbulent round jet discharging into a co-flowing stream

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