Chemical Regimes in a Post-Detonation PETN Fireball

What is it about?

The detonation of four PETN explosive charges in air were simulated in 3D Cartesian coordinates. At early times, the flow behaves in a nearly self-similar fashion. As time progresses, the air and detonation products mix and react in a mixing layer. While mixing timescales scale linearly with size, nonlinear differences in chemical time scales between the charge sizes influence the temperature and chemical composition. These differences culminate in a transition from a finite-rate regime to a mixing-limited regime in the mixing layer.

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Photo by Luke Jernejcic on Unsplash

Photo by Luke Jernejcic on Unsplash

Why is it important?

Scaled experiments are often used to explore physics at a reduced cost. However, nonlinear scaling can influence your ability to extrapolate to larger experiments. This study shows that the post-detonation flow of a relatively well oxygen balanced explosive like PETN may have noticeably different temperatures and chemical compositions between different charge sizes.