Structure of detonation fronts

It has been standard practice to base safety considerations in the design of plant on the concept of a steady unidimensional detonation front. Again, methods of controlling and preventing detonations (to be described in Chapters 7 and 8) have a similar basis, despite the existence for some time of evidence for the non-steady and multidimensional nature of detonations. There are a number of reasons for this situation. For instance, comprehensive and easily applied theories have been developed for steady waves which result in tolerable descriptions of the average properties of the wave in readily detonable media in the absence of confinement or in the presence of straight containment walls of constant cross-section. As will become increasingly apparent, comprehensive theories for structured fronts are not available. Again, since the pressures developed in contained detonations are so high, approximate estimates of their magnitude may well suffice to demonstrate that preventative measurements are necessary. However, there are situations in which a knowledge of the structure of the front is essential. In particular, it is necessary in order to understand the interactions of a detonation with a change in confinement, to estimate local pressure histories and how these may be influenced by gradients and non-uniformities in the composition of the explosive medium, so that the maximum pressure likely to be generated may be estimated.