Early development of spherical blast from a particular charge

The growth of spherical blast from a particular charge, the initial behaviour of which was analyzed in Berry & Holt (1954), is determined by numerical integration of equations of motion along characteristics. The complete field of disturbance and motion of boundaries are calculated during the early stages of development. It is found that, after a very brief outward movement, the second blast wave turns to move towards the centre of the explosion; this is in agreement with observed behaviour. The results, most of which are presented graphically, reveal a very rapid decline in pressure along both shocks, initially, and emphasize the dominating influence of the singularity at the origin of blast on the subsequent course of the disturbance. In the course of the work several new numerical techniques involved in the application of the method of characteristics are developed. Particular attention is drawn (§ 5) to the process of fitting a spherical shock wave between two non-uniform sectors of flow. The numerical method as a whole is quite general and, in later papers, application to spherical charges of other types will be described.