On self-similarity of detonation diffraction

Abstract

We consider diffraction of a detonation into an unconfined region of explosive. One might expect detonation flow to be self-similar, as in inert shock diffraction, when the reaction zone length is short compared to a geometric flow scale. One might expect that at very early time after the detonation has turned the corner, the region of explosive along the wall behaves according to the self-similar expansion for an inert flow, or as a self-similar Taylor blast wave of fixed strength. We use direct numerical simulations and study dynamic transients in self-similar coordinates to explore these hypotheses. We consider state-insensitive and state-sensitive reaction rate laws that mimic condensed explosives. We find through an analysis of shock arrival times, that the cylindrical detonation is useful in describing the dynamics of the expansion region in a two-dimensional detonation diffraction event. Therefore, we believe that detailed study of cylindrical (or spherical) detonations can be used to develop simplified or analytic models of detonation diffraction.