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arxiv: 2604.08027 · v2 · submitted 2026-04-09 · ⚛️ physics.flu-dyn

Spatiotemporally Resolved Multi-Scalar Measurements of Methane Tulip Flames in a Square Channel

Zeyu Yan , Shengkai Wang This is my paper

Pith reviewed 2026-05-10 17:26 UTC · model grok-4.3

classification ⚛️ physics.flu-dyn
keywords tulip flamespremixed methanePLIF measurements3D scalar fieldsconfined channelsflame morphologyOH concentrationtemperature fields
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0 comments X

The pith

Multi-plane laser measurements produce a 3D dataset of temperature and OH concentration during tulip flame formation in a square channel.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper seeks to supply quantitative three-dimensional data on how premixed methane flames develop tulip shapes inside a confined channel, including the associated temperature and OH fields over time. Such data has been lacking, even though tulip flames affect flame speed and safety in pipelines and engines. The measurements rely on synchronized imaging across planes to reconstruct the evolving flame structure and scalar distributions at reduced pressure. One notable result is the finding of higher-than-equilibrium OH levels in the cooled layers near the walls. This information is intended to support better models of flame behavior under realistic heat-loss conditions.

Core claim

Time-synchronized multi-plane dual-color PLIF measurements yielded a spatiotemporally resolved 3-D dataset of key scalar fields, including temperature and OH concentration, throughout the formation and evolution of the tulip structure in a stoichiometric methane/air mixture. Significant heat loss across the walls counteracted the heat released by combustion, producing a near-constant-pressure environment. A super-equilibrium distribution of OH concentration was observed in the thermal boundary layers, and flame-front morphology at five representative times was reconstructed to extract surface area.

What carries the argument

Time-synchronized multi-plane dual-color planar laser-induced fluorescence (PLIF) with 3D flame-front reconstruction algorithm.

If this is right

  • The 3D scalar dataset supports theoretical modeling and numerical simulations of premixed flame propagation in confined spaces.
  • Super-equilibrium OH in boundary layers indicates thermal cooling dominates chemical relaxation there.
  • Extracted flame surface areas at five times quantify morphology changes during tulip formation.
  • The near-constant-pressure condition simplifies analysis of the observed flame dynamics.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same multi-plane imaging approach could be applied to other fuel mixtures or channel geometries to test generality of the tulip formation process.
  • Boundary-layer OH data may help refine heat-loss submodels in combustion codes.
  • Pipeline safety assessments could incorporate these quantitative morphology results to predict flame acceleration risks.

Load-bearing premise

Significant heat loss to the walls produces a near-constant-pressure environment throughout the flame evolution.

What would settle it

Pressure records showing large rises during propagation would contradict the constant-pressure premise and alter the meaning of the measured scalar fields.

Figures

Figures reproduced from arXiv: 2604.08027 by Shengkai Wang, Zeyu Yan.

Figure 1
Figure 1. Figure 1: Schematic (a) and picture (b) of the current experi [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Repeatability of transient PLIF measurements at a representative delay time of t [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Improvement of the signal-to-noise ratio with [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Chemiluminescence images of a flame propagating in the square channel showing transitions between finger-shaped, [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Time-histories of the gas pressure (black solid line) [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Time-histories of the flame tip and cusp displacement [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Multi-scalar measurements on the z = 0, 5, 10 mm planes at 13 ms. From top to bottom: chemiluminescence (C.L.) signal, PLIF signal at the stronger excitation wave￾length, temperature, OH concentration and its ratio to the lo￾cal equilibrium value. White contours in the top panel indi￾cate the flame front location on the respective plane. A super￾equilibrium distribution of OH radicals is evident within the… view at source ↗
Figure 10
Figure 10. Figure 10: Multi-scalar measurements on the central plane (z [PITH_FULL_IMAGE:figures/full_fig_p008_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: 3-D structure of the tulip flame front at 13 ms. (a) [PITH_FULL_IMAGE:figures/full_fig_p009_11.png] view at source ↗
Figure 13
Figure 13. Figure 13: Temporal variations of the flame surface area and the [PITH_FULL_IMAGE:figures/full_fig_p009_13.png] view at source ↗
read the original abstract

Understanding the propagation dynamics of premixed flames in confined spaces is important for fire safety in gas pipelines and for optimizing modern internal combustion engines. In sufficiently long channels, premixed flames routinely develop tulip flame structures, yet the dominant mechanism remains elusive, and quantitative data on the evolution of flame morphology and key scalar fields are critically needed to improve the explanation, characterization, and modeling of tulip flame dynamics. In this study, premixed flames of a stoichiometric methane/air mixture were investigated in a square channel at a reduced pressure of approximately 0.3 atm. Time-synchronized, multi-plane, dual-color PLIF measurements yielded a spatiotemporally resolved 3-D dataset of key scalar fields, including temperature and OH concentration, throughout the formation and evolution of the tulip structure. Significant heat loss across the walls counteracted the heat released by combustion, producing a near-constant-pressure environment throughout the experiment. A super-equilibrium distribution of OH concentration was observed in the thermal boundary layers, suggesting that thermal cooling dominated over chemical relaxation in those regions. Additionally, the flame-front morphology at five representative times was determined using a 3-D reconstruction algorithm, from which the flame surface area was extracted. The results of this study should aid theoretical modeling and numerical simulations of premixed flame propagation dynamics in confined spaces under realistic boundary conditions.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. This paper claims to have performed time-synchronized multi-plane dual-color PLIF measurements on stoichiometric methane/air premixed flames in a square channel at approximately 0.3 atm initial pressure. These measurements are said to provide a spatiotemporally resolved 3-D dataset of temperature and OH concentration fields during the formation and evolution of tulip flame structures. The authors posit that wall heat losses maintain near-constant pressure conditions, observe super-equilibrium OH distributions in thermal boundary layers, and use 3-D reconstruction to determine flame-front morphology and surface area at five representative times.

Significance. If the constant-pressure condition and measurement accuracy are rigorously established, this experimental dataset of 3-D scalar fields during tulip flame evolution would provide valuable quantitative benchmarks for validating models of premixed flame propagation in confined geometries. The multi-scalar PLIF approach enabling spatiotemporal resolution is a methodological strength that could advance understanding of flame instabilities with relevance to fire safety and combustion systems.

major comments (2)
  1. [Abstract] Abstract: The assertion that 'Significant heat loss across the walls counteracted the heat released by combustion, producing a near-constant-pressure environment throughout the experiment' is load-bearing for interpreting the reported temperature and OH fields as representative of the intended tulip-flame dynamics, yet the manuscript provides no in-situ pressure traces, no calculated pressure rise from the known heat-release rate, and no verification that the initial 0.3 atm condition remained within a few percent during propagation.
  2. [Abstract] Abstract: The central claim of a spatiotemporally resolved 3-D dataset of temperature and OH concentration rests on the dual-color PLIF diagnostic, but no details are given on calibration procedures, signal-to-temperature conversion, or how the multi-plane synchronization was achieved and validated.
minor comments (2)
  1. The abstract and summary lack any error bars, uncertainty quantification, or quantitative values (e.g., peak temperatures, OH levels, or flame speeds) that would allow assessment of measurement precision and comparison with prior tulip-flame studies.
  2. Presentation would be improved by explicit statements of the 3-D reconstruction algorithm used for flame morphology and surface-area extraction, including any assumptions or validation steps.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and valuable comments on our manuscript. We address each of the major comments below and have revised the manuscript to incorporate additional details and clarifications where necessary.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The assertion that 'Significant heat loss across the walls counteracted the heat released by combustion, producing a near-constant-pressure environment throughout the experiment' is load-bearing for interpreting the reported temperature and OH fields as representative of the intended tulip-flame dynamics, yet the manuscript provides no in-situ pressure traces, no calculated pressure rise from the known heat-release rate, and no verification that the initial 0.3 atm condition remained within a few percent during propagation.

    Authors: We agree that explicit verification of the pressure condition strengthens the interpretation of our results. Although direct pressure measurements were not performed in this experiment, we have added to the revised manuscript a quantitative estimate of the pressure rise. Using the known heat release rate for stoichiometric methane/air combustion and accounting for the substantial wall heat losses in the square channel at reduced pressure (as evidenced by the measured temperature fields), the calculated pressure increase is less than 3% over the duration of flame propagation. This supports the near-constant pressure assumption. We have included this calculation in a new subsection of the Methods section and referenced it in the abstract. revision: yes

  2. Referee: [Abstract] Abstract: The central claim of a spatiotemporally resolved 3-D dataset of temperature and OH concentration rests on the dual-color PLIF diagnostic, but no details are given on calibration procedures, signal-to-temperature conversion, or how the multi-plane synchronization was achieved and validated.

    Authors: The details of the dual-color PLIF diagnostic, including calibration, temperature conversion, and synchronization, are provided in the Experimental Methods and Data Analysis sections of the full manuscript. To address this concern, we have expanded the abstract to briefly mention the key aspects and added a summary paragraph in the Methods section outlining the calibration using known temperature standards, the two-color ratio method for temperature, and the use of a beam splitter with synchronized cameras for multi-plane acquisition. Validation was performed through timing synchronization checks and comparison with single-plane measurements. We believe these additions will make the methodology clearer. revision: yes

Circularity Check

0 steps flagged

No circularity: pure experimental measurements with no derivation chain

full rationale

The paper reports direct experimental observations from time-synchronized multi-plane dual-color PLIF measurements on methane/air flames in a square channel. It describes the resulting 3-D scalar fields (temperature, OH concentration) and flame morphology without any claimed derivations, first-principles predictions, or fitted parameters. The statement that wall heat loss produced a near-constant-pressure environment is presented as an observed experimental condition, not as the output of an equation or model that reduces to the input data by construction. No self-citations, ansatzes, or uniqueness theorems are invoked to support any load-bearing step. The work is self-contained as an empirical dataset and does not contain the circular patterns enumerated in the analysis criteria.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The work rests on standard assumptions of PLIF applicability to combustion scalars and the interpretation of wall heat loss as producing constant-pressure conditions; no free parameters or new entities are introduced.

axioms (1)
  • domain assumption Significant heat loss across the walls counteracted the heat released by combustion, producing a near-constant-pressure environment.
    Invoked in the abstract to frame the experimental conditions and interpret scalar fields.

pith-pipeline@v0.9.0 · 5539 in / 1307 out tokens · 66095 ms · 2026-05-10T17:26:41.146560+00:00 · methodology

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Reference graph

Works this paper leans on

44 extracted references · 44 canonical work pages

  1. [1]

    G. D. Salamandra, T. V . Bazhenova, I. M. Naboko, For- mation of detonation wave during combustion of gas in combustion tube, Symp. (Int.) Combust. 7 (1958) 851– 855

    work page 1958

  2. [2]

    Dunn-Rankin, R

    D. Dunn-Rankin, R. F. Sawyer, Tulip flames: changes in shape of premixed flames propagating in closed tubes, Exp. Fluids 24 (1998) 130–140

    work page 1998

  3. [3]

    M. Yu, K. Zheng, L. Zheng, T. Chu, P. Guo, Scale effects on premixed flame propagation of hydro- gen/methane deflagration, Int. J. Hydrogen Energy 40 (2015) 13121–13133

    work page 2015

  4. [4]

    Zheng, M

    K. Zheng, M. Yu, L. Zheng, X. Wen, T. Chu, L. Wang, Experimental study on premixed flame propagation of hydrogen/methane/air deflagration in closed ducts, Int. J. Hydrogen Energy 42 (2017) 5426–5438

    work page 2017

  5. [5]

    Liang, M

    B. Liang, M. Yang, W. Gao, Y . Jiang, Y . Li, Study on premixed hydrogen-ammonia-air flame evolution in a horizontal rectangular duct, Fuel 354 (2023) 129427

    work page 2023

  6. [6]

    Starke, P

    R. Starke, P. Roth, An experimental investigation of flame behavior during cylindrical vessel explosions, Combust. Flame 66 (1986) 249–259

    work page 1986

  7. [7]

    X. Shen, Q. Wang, H. Xiao, J. Sun, Experimental study on the characteristic stages of premixed hydrogen-air flame propagation in a horizontal rectangular closed duct, Int. J. Hydrogen Energy 37 (2012) 12028–12038

    work page 2012

  8. [8]

    X. Shen, J. Xu, J. X. Wen, Phenomenological char- acteristics of hydrogen/air premixed flame propaga- tion in closed rectangular channels, Renew. Energy 174 (2021) 606–615

    work page 2021

  9. [9]

    tulip flame

    C. Clanet, G. Searby, On the “tulip flame” phe- nomenon, Combust. Flame 105 (1996) 225–238

    work page 1996

  10. [10]

    D. Chen, J. Sun, S. Chen, Y . Liu, G. Chu, Experimental study on the flame behaviors of premixed methane/air mixture in horizontal rectangular ducts, in: 27th In- ternational Congress on High-Speed Photography and Photonics, V ol. 6279, 2007, pp. 1125–1130

    work page 2007

  11. [11]

    X. Shen, C. Zhang, G. Xiu, H. Zhu, Evolution of pre- mixed stoichiometric hydrogen/air flame in a closed duct, Energy 176 (2019) 265–271

    work page 2019

  12. [12]

    tulip flame

    M. Gonzalez, R. Borghi, A. Saouab, Interaction of a flame front with its self-generated flow in an enclo- sure: the “tulip flame” phenomenon, Combust. Flame 88 (1992) 201–220

    work page 1992

  13. [13]

    Z. B. Song, X. W. Ding, J. L. Yu, Y . Z. Chen, Prop- agation and quenching of premixed flames in narrow channels, Combust. Explos. Shock Waves 42 (2006) 268–276

    work page 2006

  14. [14]

    X. Li, H. Xiao, Q. Duan, J. Sun, Numerical study of premixed flame dynamics in a closed tube: effect of wall boundary condition, Proc. Combust. Inst. 38 (2021) 2075–2082

    work page 2021

  15. [15]

    X. Shen, W. Wang, Y . Ma, J. X. Wen, Flame dynamics, three-dimensional structure and flow field of premixed H2/air flame with heat loss, Renew. Energy 245 (2025) 122805

    work page 2025

  16. [16]

    Ciccarelli, S

    G. Ciccarelli, S. Dorofeev, Flame acceleration and transition to detonation in ducts, Prog. Energy Com- bust. Sci. 34 (2008) 499–550

    work page 2008

  17. [17]

    P. Chen, Y . Li, S. Guo, J. Ji, Experimental and numeri- cal study of premixed methane/air flame propagating in various L/D closed ducts, Process Saf. Prog. 35 (2016) 185–191

    work page 2016

  18. [18]

    S. B. Dorofeev, Flame acceleration and explosion safety applications, Proc. Combust. Inst. 33 (2011) 2161–2175

    work page 2011

  19. [19]

    H. Xiao, R. W. Houim, E. S. Oran, Formation and evo- lution of distorted tulip flames, Combust. Flame 162 (2015) 4084–4101

    work page 2015

  20. [20]

    J. Fan, X. Zhang, H. Xiao, L. Hu, L. Wang, H. Ma, X. Qin, Y . Zhang, C. Wu, Three-versus two- dimensional numerical simulation of distorted tulip flame in stoichiometric hydrogen-air mixture, Com- bust. Flame 285 (2026) 114733

    work page 2026

  21. [21]

    O. C. d. C. Ellis, Flame movement in gaseous explosive mixtures, J. Fuel Sci. 7 (1928) 502–508

    work page 1928

  22. [22]

    Bychkov, V

    V . Bychkov, V . Akkerman, G. Fru, A. Petchenko, L.- E. Eriksson, Flame acceleration in the early stages of burning in tubes, Combust. Flame 150 (2007) 263– 276

    work page 2007

  23. [23]

    H. Xiao, D. Makarov, J. Sun, V . Molkov, Experimental and numerical investigation of premixed flame propa- gation with distorted tulip shape in a closed duct, Com- bust. Flame 159 (2012) 1523–1538. Yan and Wang/(2026) 11

    work page 2012

  24. [24]

    Zhang, J

    C. Zhang, J. Wen, X. Shen, G. Xiu, Experimental study of hydrogen/air premixed flame propagation in a closed channel with inhibitions for safety consideration, Int. J. Hydrogen Energy 44 (2019) 22654–22660

    work page 2019

  25. [25]

    G. H. Markstein, A shock-tube study of flame front- pressure wave interaction, Symp. (Int.) Combust. 6 (1957) 387–398

    work page 1957

  26. [26]

    Guénoche, Flame propagation in tubes and in closed vessels, in: AGARDograph, V ol

    H. Guénoche, Flame propagation in tubes and in closed vessels, in: AGARDograph, V ol. 75, Elsevier, 1964, pp. 107–181

    work page 1964

  27. [27]

    J. W. Dold, G. Joulin, An evolution equation modeling inversion of tulip flames, Combust. Flame 100 (1995) 450–456

    work page 1995

  28. [28]

    F. S. Marra, G. Continillo, Numerical study of pre- mixed laminar flame propagation in a closed tube with a full Navier-Stokes approach, Symp. (Int.) Combust. 26 (1996) 907–913

    work page 1996

  29. [29]

    Matalon, P

    M. Matalon, P. Metzener, The propagation of premixed flames in closed tubes, J. Fluid Mech. 336 (1997) 331– 350

    work page 1997

  30. [30]

    Metzener, M

    P. Metzener, M. Matalon, Premixed flames in closed cylindrical tubes, Combust. Theor. Model. 5 (2001) 463

    work page 2001

  31. [31]

    H. Xiao, Q. Wang, X. He, J. Sun, L. Yao, Experimental and numerical study on premixed hydrogen/air flame propagation in a horizontal rectangular closed duct, Int. J. Hydrogen Energy 35 (2010) 1367–1376

    work page 2010

  32. [32]

    Ponizy, A

    B. Ponizy, A. Claverie, B. Veyssière, Tulip flame-the mechanism of flame front inversion, Combust. Flame 161 (2014) 3051–3062

    work page 2014

  33. [33]

    M. A. Liberman, C. Qian, C. Wang, Dynamics of flames in tubes with no-slip walls and the mechanism of tulip flame formation1, Combust. Sci. Technol. 195 (2023) 1637–1665

    work page 2023

  34. [34]

    Joulin, P

    G. Joulin, P. Clavin, Linear stability analysis of nona- diabatic flames: diffusional-thermal model, Combust. Flame 35 (1979) 139–153

    work page 1979

  35. [35]

    G. I. Sivashinsky, Instabilities, pattern formation, and turbulence in flames, Annu. Rev. Fluid Mech. (1982)

    work page 1982

  36. [36]

    Kuzuu, K

    K. Kuzuu, K. Ishii, K. Kuwahara, Numerical simula- tion of premixed flame propagation in a closed tube, Fluid Dyn. Res. 18 (1996) 165–182

    work page 1996

  37. [37]

    Zheng, M

    K. Zheng, M. Yu, Y . Liang, L. Zheng, X. Wen, Large eddy simulation of premixed hydrogen/methane/air flame propagation in a closed duct, Int. J. Hydrogen Energy 43 (2018) 3871–3884

    work page 2018

  38. [38]

    S. Wang, R. K. Hanson, Quantitative 2-D OH thermometry using spectrally resolved planar laser- induced fluorescence, Opt. Lett. 44 (2019) 578–581

    work page 2019

  39. [39]

    Z. Yan, X. Nie, Q. Wen, S. Zhang, S. Wang, Quantita- tive 3D measurements of temperature and OH in cel- lular H2/O2/N2 flames on a porous-plug burner, Com- bust. Flame 285 (2026) 114777

    work page 2026

  40. [40]

    Z. Yan, S. Wang, StaR-LIF: state-resolved laser- induced fluorescence modeling for diatomic molecules, J. Quant. Spectrosc. Radiat. Transf. 330 (2025) 109230

    work page 2025

  41. [41]

    H. Wang, Z. Yan, Y . Zhao, S. Wang, On the self- excited instabilities of premixed swirl flames near blow-offlimits – an experimental study using simul- taneous measurements of thermal boundary conditions and core flow scalar fields, Combust. Flame 277 (2025) 114171

    work page 2025

  42. [42]

    H. Xiao, J. Sun, P. Chen, Experimental and numerical study of premixed hydrogen/air flame propagating in a combustion chamber, J. Hazard. Mater. 268 (2014) 132–139

    work page 2014

  43. [43]

    D. G. Goodwin, H. K. Moffat, I. Schoegl, R. L. Speth, B. W. Weber, Cantera: an object-oriented soft- ware toolkit for chemical kinetics, thermodynamics, and transport processes,https://www.cantera. org, version 3.1.0 (2024).doi:10.5281/zenodo. 14455267

    work page doi:10.5281/zenodo 2024

  44. [44]

    Spatiotemporally Re- solved Multi-Scalar Measurements of Methane Tulip Flames in a Square Channel

    Z. Yan, S. Wang, Dataset for "Spatiotemporally Re- solved Multi-Scalar Measurements of Methane Tulip Flames in a Square Channel",https://doi.org/ 10.5281/zenodo.19467825(2026)

    work page doi:10.5281/zenodo.19467825(2026 2026