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| 2001-2002 Fluids Seminar Page |
Laboratory for Computational Physics and Fluid Dynamics,
Naval Research Laboratory,
Washington, DC
Abstract-
The mechanism by which a high-speed deflagration becomes a detonation (deflagration-to-detonation
transition, or DDT) remains as an outstanding problem in combustion theory. DDT is an extremely
complex process involving deflagration, shocks, boundary layers, and all of their interactions with each
other.
The process of DDT for conditions similar to reflected shock-tube experiments in acetylene-air and
ethylene-air mixtures is investigated using two- and three-dimensional reactive Navier-Stokes
fluid-dynamics simulations. A dynamically adapting mesh is used to
resolve flames, shocks, boundary layers, and vortices in flow. Simulations reveal a complex sequence
of events, starting from the interaction of an incident shock with an initially laminar flame and the
formation of a flame brush.
Boundary layers have a major effect on shock-flame interaction and DDT.
Shock bifurcations caused by boundary layers create multi-dimensional shock-flame
structures with a flame entrained in the recirculation region and moving with the speed of the bifurcated
shock. The DDT process finally leads to the emergence of a self-sustained cellular detonation.
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