### Abstract

The curvature of turbulent premixed flame fronts is an important spatial property that needs to be quantified over a range of turbulence conditions. In this study, measurements of flamelet curvature along with orientation statistics for u'/S_{L}— 1.42-5.71 are obtained from OH planar laser-induced fluorescence images of the flame boundary by applying a curve-tracing difference formula with interval length of the order of the inner cutoff scale. Use of this particular interval length is essential for accurate tracing of the flame boundary with implicit filtering of extraneous noise that can introduce significant errors in the curvature measurements. The distributions of flamelet curvature are found to be symmetric with respect to the zero mean, while the variance increases with increasing u'/S_{L}. These distributions can be approximated by Gaussian distribution functions. The positive and negative mean curvatures show a nearly square-root dependence on u’/S_{L}, whereas the mean flamelet radius of curvature is approximately a factor of two larger than the Taylor scale of turbulence in the approach flow. The effect of Lewis number on flamelet curvature is evidenced by a 20% increase in mean cuvatures which is attributed to the unstable flame fronts at Lewis number less than unity. The evolution of flamelet orientation with increasing u'/S_{L}shows a trend toward isotropy, which is estimated to prevail when u’ becomes an order of magnitude larger than S_{L}. For unstable flame fronts (Le &; 1), flamelets are more randomly orientated and thus isotropy may be achieved for somewhat smaller ratio of u'/S_{L}.

Original language | English (US) |
---|---|

Pages (from-to) | 121-132 |

Number of pages | 12 |

Journal | Combustion Science and Technology |

Volume | 84 |

Issue number | 1-6 |

DOIs | |

State | Published - Jul 1 1992 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Chemical Engineering(all)
- Chemistry(all)
- Energy Engineering and Power Technology
- Fuel Technology
- Physics and Astronomy(all)

### Cite this

*Combustion Science and Technology*,

*84*(1-6), 121-132. https://doi.org/10.1080/00102209208951848

**Curvature and Orientation Statistics of Turbulent Premixed Flame Fronts.** / Lee, Taewoo; North, G. L.; Santavicca, D. A.

Research output: Contribution to journal › Article

*Combustion Science and Technology*, vol. 84, no. 1-6, pp. 121-132. https://doi.org/10.1080/00102209208951848

}

TY - JOUR

T1 - Curvature and Orientation Statistics of Turbulent Premixed Flame Fronts

AU - Lee, Taewoo

AU - North, G. L.

AU - Santavicca, D. A.

PY - 1992/7/1

Y1 - 1992/7/1

N2 - The curvature of turbulent premixed flame fronts is an important spatial property that needs to be quantified over a range of turbulence conditions. In this study, measurements of flamelet curvature along with orientation statistics for u'/SL— 1.42-5.71 are obtained from OH planar laser-induced fluorescence images of the flame boundary by applying a curve-tracing difference formula with interval length of the order of the inner cutoff scale. Use of this particular interval length is essential for accurate tracing of the flame boundary with implicit filtering of extraneous noise that can introduce significant errors in the curvature measurements. The distributions of flamelet curvature are found to be symmetric with respect to the zero mean, while the variance increases with increasing u'/SL. These distributions can be approximated by Gaussian distribution functions. The positive and negative mean curvatures show a nearly square-root dependence on u’/SL, whereas the mean flamelet radius of curvature is approximately a factor of two larger than the Taylor scale of turbulence in the approach flow. The effect of Lewis number on flamelet curvature is evidenced by a 20% increase in mean cuvatures which is attributed to the unstable flame fronts at Lewis number less than unity. The evolution of flamelet orientation with increasing u'/SLshows a trend toward isotropy, which is estimated to prevail when u’ becomes an order of magnitude larger than SL. For unstable flame fronts (Le &; 1), flamelets are more randomly orientated and thus isotropy may be achieved for somewhat smaller ratio of u'/SL.

AB - The curvature of turbulent premixed flame fronts is an important spatial property that needs to be quantified over a range of turbulence conditions. In this study, measurements of flamelet curvature along with orientation statistics for u'/SL— 1.42-5.71 are obtained from OH planar laser-induced fluorescence images of the flame boundary by applying a curve-tracing difference formula with interval length of the order of the inner cutoff scale. Use of this particular interval length is essential for accurate tracing of the flame boundary with implicit filtering of extraneous noise that can introduce significant errors in the curvature measurements. The distributions of flamelet curvature are found to be symmetric with respect to the zero mean, while the variance increases with increasing u'/SL. These distributions can be approximated by Gaussian distribution functions. The positive and negative mean curvatures show a nearly square-root dependence on u’/SL, whereas the mean flamelet radius of curvature is approximately a factor of two larger than the Taylor scale of turbulence in the approach flow. The effect of Lewis number on flamelet curvature is evidenced by a 20% increase in mean cuvatures which is attributed to the unstable flame fronts at Lewis number less than unity. The evolution of flamelet orientation with increasing u'/SLshows a trend toward isotropy, which is estimated to prevail when u’ becomes an order of magnitude larger than SL. For unstable flame fronts (Le &; 1), flamelets are more randomly orientated and thus isotropy may be achieved for somewhat smaller ratio of u'/SL.

UR - http://www.scopus.com/inward/record.url?scp=0000140010&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000140010&partnerID=8YFLogxK

U2 - 10.1080/00102209208951848

DO - 10.1080/00102209208951848

M3 - Article

VL - 84

SP - 121

EP - 132

JO - Combustion Science and Technology

JF - Combustion Science and Technology

SN - 0010-2202

IS - 1-6

ER -