ID#: 27
Abstract Title: Effects of Boundary Layers on Shock-flame Interaction and DDT
Session Title: DDT
Session Date: 7/31/01
Session Start Time: 8:30 AM
Contributing Author: Khokhlov, A.M.
Organization: Naval Research Laboratory
Country: USA
Authors: Vadim N. Gamezo, Alexei M. Khokhlov, Elaine S. Oran
Short Abstract: The effects of boundary layers on shock-flame interactions and deflagration-to-detonation transition (DDT) are investigated using two- and three-dimensional, time-dependent, reactive Navier-Stokes fluid-dynamics simulations of shock-tube experiments. Simulations show a complex sequence of events, starting from the interactions of an incident shock with a laminar flame and the formation of a flame brush. The bifurcation of the reflected shock, due to boundary layer effects, creates a rapidly growing, leading oblique shock followed by a recirculation region. Flame becomes entrained in the recirculation region and attached to the bifurcated shock. Three-dimensional simulations show that the highly-deformed flame surface is spread out through the entire region between the reflected shock and the end-wall. The schlieren pictures made from three-dimensional data show a reflected shock followed by an approximately constant-volume region of burning. The burning region moves with the velocity of the reflected shock and is characterized by the pressure that is less than the pressure of a Chapmen-Jouguet detonation. A reactive bifurcated structure increases the energy-release rate in the system, leads to the formation of Mach stems in the middle of the shocktube, and generates multiple hot spots behind the Mach stem, thus facilitating DDT. The DDT process finally leads to the emergence of a self-sustained cellular detonation.