Prediction of explosive effects

Both courts and police investigators need to be able to understand the potential effects of a particular explosive or explosive device and to be able to set it into its proper context. For example was this a mere firework being misused by a naughty schoolboy, or a weapon of mass destruction That is not, of course, to forget that devices illegally constructed from fireworks can cause horrific injuries. 

The nature of the explosive involved in a particular incident may be inferred from statements made by suspects or witnesses, from evidential material seized by investigators, or from chemical analysis. Expert scientific evidence about the fikely performance and effect of a suspect explosive will be needed to assist the relevant court in its deliberations. If the explosive is a well-known mifitary or commercial type then this is relatively straightforward. In the case of improvised or home-made explosives the issues can be more complex. This is particularly so where individuals have been experimenting with unusual chemicals. Unless the scientist has previous experience of the materials involved, the first step is fikely to be a search of the relevant literature [28-30]. 

Calculations can also be helpful. The defence departments of various countries have developed sophisticated computer codes for the prediction and analysis of explosive effects. However not only are these not generally published which makes forensic review and scrutiny difficult, but they are also designed for use with mifitary materials and may be less applicable to home-made explosives. 

A widely recognised approach uses the modified Kistiakowsky—Wilson rules to predict the chemical products from an explosion, and then the Berthelot approximation to evaluate the explosive output compared with a standard explosive, usually TNT. 

The first step is to devise a set of decomposition reactions, assuming the transformation of the reactants (i.e. explosive ingredients) into their constituent elements. 

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The 3D CFD computer code FLAGS (Flame Acceleration Simulator) developed at the Christian-Michelson Institute in Bergen, Norway, is able to handle complete chemical processing plants down to the level of piping. The code treats spreading and combustion of flammable gases and determines concentration distributions and the impact on structures from explosions. Its main application is the prediction of explosion effects in offshore geometries [118]. 

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