The transient interaction of flames with obstacles is a key phenomenon in determining the severity of turbulent gaseous explosions. In the present work the transition of a confined, initially laminar, stoichiometric methane-air flame to a strongly turbulent deflagration caused by its interaction with a baffle-type obstacle has been studied in detail. Time-dependent flow characteristics, including velocity vectors and Reynolds stress components, have been determined in a two-dimensional plane along the vertical tube axis through the use of Laser Doppler Anemometry (LDA). Estimates of turbulence production and the dissipation rate of turbulence have also been extracted. The configuration used yields a significant explosion with an over-pressure close to 100 kPa and peak (mean) how velocities approaching 100 m/s. Typical rms velocities are of the order 4 m/s and significant levels of anisotropy are observed in the shear layer above the obstacle. It is shown that for the geometry studied the turbulent rate of strain significantly exceeds the bulk rate of strain. Measurements through the turbulent flame brush also indicate that in the absence of mean velocity gradients the turbulence intensities are unchanged or marginally enhanced by the presence of the flame. The comprehensive nature of the present data set is expected to enable significant progress to be made in the development/validation of models for turbulent gaseous explosions. (C) 1998 by The Combustion Institute. References: 42
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