19. On the Theory and Modelling of Flame Acceleration and Deflagration-to-Detonation Transition

Prevention of spontaneous premixed flame acceleration (FA) and deflagration (flame)-to-detonation transition (DDT) would avoid thousands of fatalities and injuries that occur every year in numerous disasters such as accidental mining or power plants explosions. On the other hand, promotion of FA and DDT can be energeticallyefficiently employed in the emerging technologies such as pulse-detonation engines and micro-combustors. Fundamentally, the DDT applications range from terrestrial burning and inertial confined fusion to thermonuclear supernovae and crystals of molecular/nano-magnets. In all these respects, the physical understanding and quantitative description of FA and DDT are critically needed from both practical and fundamental viewpoints. This need is addressed here, with a focus on combustion tubes/channels as the primary geometry. Specifically, various mechanisms of FA in pipes such as those due to (i) wall friction, (ii) in-built obstacles, and (iii) a finger flame shape are described, with various stages of FA and DDT scenarios being simulated and quantified. The locus and timing of detonation initiation, triggered by an accelerating flame front, are prescribed.