Summary:
A detonation is characterized by a configuration of a discontinuous hydrodynamic shock wave followed by a smooth region of decaying combustion. The shock causes an adiabatic compression, which rises the temperature of the combustible mixture above the ignition limit. After the ignition, it takes an induction time of a few microseconds, until the reactants start to react rapidly to the constant equilibrium state. The chemical reaction results in an energy release that drives the shock wave forward. In a self-sustaining detonation, shock and reaction zone propagate essentially with an identical wave speed, which is approximately equal to the ChapmanJouguet (CJ) velocity. The CJ value is the minimal velocity of a discontinuous wave separating reactants and equilibrium products and can be calculated from the Chapman-Jouguet theory.
The evolution of the initial transverse waves shown in the above sequences of images illustrate the transition of the detonation in which there is a steadily repeating pattern of two triple points. Another interesting observation comes from the temperature contours shown above. Such images show an unstable slip line as the Mach stem evolves and a low temperature region behind the Mach stem the inflection point. This indicates that the reaction front and the Mach stem are not coupled. This leads to a weak energy release behind the detonation. The same contour also show a hingly unstable slip-line. The strenght of such slip line is defined in terms of the strength of the vortex sheet across it.
