Deflagration-to-Detonation Transition (DDT)
Definition
The acceleration of a deflagrating burn front to supersonic detonation velocity, triggered by confinement. Relevant to understanding how improvised devices using low explosives in confined containers can produce detonation-like effects.
- Flame speed transition
- From subsonic (deflagration) to supersonic (detonation)
- Primary driver
- Confinement and pressure run-up
Common questions
What happens during deflagration-to-detonation transition?+
A deflagration (subsonic burn) accelerates to detonation (supersonic shock) when turbulent flame acceleration and pressure build up enough under confinement. This typically happens inside confined spaces like sealed pipes or containers. The result is mixed scene signatures, where physical evidence reflects characteristics of both the initial deflagration and the resulting detonation.
Why do low explosives sometimes produce detonation-like effects?+
Low explosives normally burn subsonically, but when confined in a sealed container, confinement drives turbulent flame acceleration and pressure run-up to detonation velocity. This DDT mechanism explains why seemingly weak materials can cause severe damage in improvised devices.
What role does confinement play in DDT?+
Confinement is the key trigger. As the flame front accelerates, pressure builds against the confining walls and turbulent flame acceleration intensifies, together driving the burn to detonation velocity. Without confinement, a deflagration stays subsonic.
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Explained in these topics
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