Deflagrationtodetonation

Deflagration-to-detonation transition (DDT) is the process by which a subsonic combustion wave, known as a deflagration, evolves into a detonation, which is a supersonic shock-driven combustion wave. In a deflagration, heat and species diffusion sustain flame propagation, while a detonation travels at high speed with a leading shock front that compresses and ignites the reactive mixture behind it.

DDT is particularly relevant in confined or turbulent environments, such as gas pipelines, vessels, or porous geometries, where interactions between the flame, obstacles, and pressure waves can create local shocks and hotspots. These interactions may compress and heat unburned gas to conditions that auto-ignite, enabling a transition to a self-sustaining detonation. The process is not instantaneous and often depends on factors such as mixture composition, initial pressure and temperature, confinement, and turbulence intensity.

Detonations feature a characteristic, highly structured reaction zone and a shock front, with wave speeds determined by the Chapman–Jouguet framework and often exhibiting cellular patterns due to the dynamic interactions of shocks and reactions. The Zeldovich–von Neumann–Döring (ZND) theory provides a fundamental description of the detonation structure, while modern analyses use experiments and numerical simulations to study the transition and its thresholds.

DDT has practical significance for safety and design in industries handling reactive gases. Understanding the conditions under which a deflagration may transition to detonation informs risk assessment, mitigation strategies, and the development of explosion-resistant geometries and operating procedures.