Direct initiation of detonation by non-ideal blast waves

This study is a theoretical investigation of the initiation of detonation by nonideal blast waves. The study used the output of the CLOUD program as the source of flow data for blast waves generated by bursting spheres. Each cell that surrounds the bursting sphere is assumed to be reactive with an Arrhenius type kinetic rate law over a temperature range of from 1000 - 2700 K. Outside this range the cell is assumed to be nonreactive. In the technique the delay to explosion is integrated numerically from the time of shock passage over that cell until the temperature of the cell drops below 1000 K. A minimum of this summation time was found for cells either near the bursting sphere or right at the edge of the sphere. Conceptually, as the bursting sphere is made larger and larger one eventually reaches a point at which the delay time to explosion in at least one of the cells is long enough such that an explosion process can start. This is taken as the criterion for detonation initiation in this model. Numerous cases were run and initiation behavior was plotted both as a function of the total energy of the bursting sphere and the energy density of the bursting sphere. In addition, a few runs were made for the ramp edition of energy to compare to the bursting sphere results. The study shows that as the energy density of the sphere gas becomes lower the total energy required for initiation increases sharply. This is in agreement with experimental studies using spark initiation.