The Strain Exerted by a Vortex on a Flame—Determined from Velocity Field Images

Driscoll, James F.; Sutkus, D. J.; Roberts, William L.; Post, M. E.; Goss, L. R

doi:10.1080/00102209408935356

Cited by 53 publications

(16 citation statements)

References 16 publications

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“…The magnitudes of this negative U-velocity distribution are augmented in the case of pre-heating effects compared to non pre-heating effect as the flame front has experienced an extreme deformation due to pre-heating effect. The appearance of this negative velocity is consistent with the results observed by Driscoll et al [31]. But the magnitude of the negative velocity for non pre-heating effect is much lower whereas for pre-heating effect it is higher compared with that of the results reported by Driscoll et al [31].…”

Section: Resultssupporting

confidence: 82%

“…The appearance of this negative velocity is consistent with the results observed by Driscoll et al [31]. But the magnitude of the negative velocity for non pre-heating effect is much lower whereas for pre-heating effect it is higher compared with that of the results reported by Driscoll et al [31]. Further inspection revealed that the magnitude of the negative velocity is high along the center line and its close vicinity in ahead of the flame tips.…”

Section: Resultssupporting

confidence: 82%

“…7. This observation is also consistent with the results reported by Driscoll et al [31]. In this sense, the strong deformation of flame induces the appearance of pair vortex in ahead of flame tip.…”

Section: Pair Of Vortexsupporting

confidence: 83%

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Numerical Study of an In-line Pre-Heating Treatment along the Axis on the Propagation of a Laminar Premixed Flame in a Channel

Hossain

Oshima

Nakamura

et al. 2009

JTST

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In this study, an in-line pre-heating effect on the propagation of a laminar premixed flame in a two-dimensional channel is investigated numerically. An in-line pre-heating thickness of 1mm is generated by imposing uniform external high-temperature along the center line in the prescribed channel. It is found that the shapes of flame and propagation speeds are strongly affected by the pre-heating effect. The distribution of velocity pointed to ahead of the propagating flame (called negative velocity hereafter) is clearly observed which is susceptible to the generation of the pair of vortex in ahead of the flame tip. The evolution of negative flow field in front of premixed flame is successfully captured first ever in a time-dependent manner. The obtained flame propagation accompanied with the aforementioned negative velocity field is not only useful to elucidate the laser induced flame instability reported recently by Tsuchimoto et al. (2007), but also to consider the pure thermal effect on flame evolution, which is hard to obtain experimentally.

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Section: Resultssupporting

confidence: 82%

Section: Resultssupporting

confidence: 82%

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Numerical Study of an In-line Pre-Heating Treatment along the Axis on the Propagation of a Laminar Premixed Flame in a Channel

Hossain

Oshima

Nakamura

et al. 2009

JTST

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“…Driscoll et al [22] determined aerodynamic strain rate, rate of flame stretch, vorticity, and shear strain rate during a flame-vortex interaction. Similarly, Mueller et al [23] studied repeatable flamevortex interactions from the wrinkled flamelet to local extinction regimes and generated a time history of flame stretch, strain, and vorticity.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous CH planar laser-induced fluorescence and particle imaging velocimetry in turbulent nonpremixed flames

Carter

Donbar

Driscoll

1998

Applied Physics B: Lasers and Optics

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The present work addresses the question of whether the chemical reaction zone within a turbulent, high-Reynolds-number jet flame is thin-and can be modeled using strained wrinkled laminar flamelet theory-or is thick-and must be modeled using distributed reaction zone theory. The region near the wrinkled instantaneous stoichiometric contour is identified using CH Planar Laser-Induced Fluorescence (PLIF) imaging and the strain on this interface is measured using simultaneous Particle Imaging Velocimetry (PIV) diagnostics. With a separate set of simultaneous images, the relative position of the CH and OH radicals is observed using PLIF. It is found that the CH reaction zone remains thin and rarely exceeds 1 mm, even near the flame tip in a high-Reynolds-number (18,600) jet flame. The mean thickness of the CH reaction layer (5 C H) increases from 0.3 to 0.8 mm in the streamwise direction; this is expected because the scalar dissipation rate is known to decrease with downstream distance and should cause a corresponding increase in 8 CH . However, 8 CH also increases with jet velocity, which is not predicted by theory. Furthermore, the mean strain rates on the stoichiometric contour increase in the streamwise direction, which is contrary to previous predictions. Thus, strain rate does not, in general, scale with the local dissipation rate in a turbulent flame, and this aspect of the counterflow flow analogy is not valid. It is concluded that unsteady laminar flamelet concepts are consistent with most of the present observations, but a method independent of the local dissipation rate is needed to predict the local strain rate. IntroductionOften, the analogy is made between segments of turbulent nonpremixed jet flames and a steady laminar counterflow diffusion flame that is selected to have the same strain rate as the turbulent flame segment; particularly, this analogy is used in "laminar flamelet models" [1,2]. The flamelet regime, by definition, exists over regions in which the flame front is thinner than the smallest scale of turbulence, and thus the flame front can be modeled as an ensemble of laminar flamelets. For the flamelet analogy to be realistic, several factors must be known: 1. if the reaction layers are sufficiently thin (rather than thick, distributed zones); 2. if the reaction-layer properties (e.g. radical concentrations, thickness) scale as predicted by counterflow theory; 3. how frequently the layers extinguish or merge; and 4. if the strain on the turbulent reaction layers is proportional to the dissipation rate as in counterflow flames [2]. If all of these conditions are satisfied, it becomes possible to apply several promising modeling ideas which draw heavily on flamelet theory, including the original flamelet model [2], the Local Integral Moment (LIM) model [3,4], the Large Eddy Simulation (LES) model [5], and Direct Numerical Simulation (DNS) [6]. To date, lack of information on the structure of turbulent

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“…The role of the laminar flame thickness was recognized as an important parameter for study and comprehension of the flame/turbulence interactions [9]. Various studies have tried to analyze the influence of chemical reaction due to combustion on turbulence field flame [3,4,[10][11][12][13][14]. Chekired et al [15] using Peters and Williams mechanism, showed good agreement between the numerical results and the experimental ones of the Aachen flame F3.…”

Section: Introductionmentioning

confidence: 65%

Experimental study of the dynamic field of turbulent premixed methane/air flame using PIV technique

Boulahlib¹,

Chekired²,

Benzitouni³

et al. 2016

Int. J. CMEM

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This work is an experimental study of the dynamic fields of a turbulent premixed methane-air flame in a Bunsen burner. The Particle Image Velocimetry (PIV) is used to determine the dynamic fields, and Laser Sheet Tomography (LST) for the flame fronts. The turbulent main jet has a Reynolds number Re = 10 000. Turbulence is generated using perforated grids having three whose provide different inlet turbulence intensities. Velocity fields are measured for various equivalence ratio (F = 0.6-1.3) and different axial flame positions. For the reactive jet, interesting results are obtained concerning the dynamic field and the flame front. It is shown that radial profiles of U and V correspond to the axial positions located before the end of the potential core in the reactive jet. The velocity increases at the jet center to 20 m/s, and is less influenced by turbulent mixing in the flame. The greatest velocity and turbulent kinetic energy are obtained using the grid with the smallest ratio (d/M). Most important values of the radial velocity correspond to the lean flames.

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The Strain Exerted by a Vortex on a Flame—Determined from Velocity Field Images

Cited by 53 publications

References 16 publications

Numerical Study of an In-line Pre-Heating Treatment along the Axis on the Propagation of a Laminar Premixed Flame in a Channel

Numerical Study of an In-line Pre-Heating Treatment along the Axis on the Propagation of a Laminar Premixed Flame in a Channel

Simultaneous CH planar laser-induced fluorescence and particle imaging velocimetry in turbulent nonpremixed flames

Experimental study of the dynamic field of turbulent premixed methane/air flame using PIV technique

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