Flame curvature statistics in axisymmetric turbulent jet flames

Flame curvature in axisymmetric turbulent jet flames are obtained experimentally for u'/S-L from 0.8-1.5. The measurements indicate that the flame curvature statistics exhibit a substantial change as a function of the axial location in turbulent jet flames primarily due to the evolution of flame wrinkle structures. In particular, it is found that the flame curvature tends to be very small near the burner exit, while development of the flame wrinkle structures further from the burner exit results in an increase in magnitude and asymmetry in flame curvature probability density functions (pdf's). The mean flame curvature in the vertical plane is close to zero in spite of the asymmetry in the flame curvature pdf's except near the flame tip where the mean flame curvature becomes negative due to the frequent occurrences of cusps. In contrast, the flame curvature in the horizontal plane are strongly affected by the burner dimension and geometry in that the magnitude of both positive and negative fame curvatures are increased by the finite curvature of the conical jet flame shape in the mean. The mean flame curvature in the horizontal plane tends to be of the order of the burner radius. The flame orientation statistics of turbulent jet flames have also been obtained, which show a similar evolution as a function of the distance from the burner exit.