New evidence for the role of turbulence in the ignition of secondary flash

The first precursor flow of a 7.62 mm rifle has been photographed by schlieren and shadowgraph techniques and has been probed by a laser Doppler velocimeter. The results indicate that slip line formation is hindered downstream from the Mach disk, in the main flow at the critical time of intermediate flash formation. These results support the supposition that turbulence is an important process in the intermediate flash region. Specifically, the turbulence may permit oxygen to be entrained and transported even to the axis of the intermediate flash region where combustion processes may take place. These processes are assumed to be necessary in the ignition sequence leading to the formation of secondary flash.