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Tuesday, March 24, 2009

The Laminar Flame to Turbulent Flame to Detonation Transition: Studies of Non-Kolmogorov Turbulence and Stochasticity

The Laminar Flame to Turbulent Flame to Detonation Transition: Studies of Non-Kolmogorov Turbulence and Stochasticity

Abstract


The transition from a propagating subsonic Laminar flame to a high-speed Turbulent flame and then to supersonic Detonation wave (the LTD transition) involves a series of often dramatic events involving changes in the nature of the reaction wave. Some of the events develop continuously whereas others appear suddenly and with little apparent warning. The LTD transition occurs in highly exothermic energetic materials, for example in hydrogen-air mixtures resulting from gas leaks at hydrogen production and storage facilities as well as in carbon-oxygen mixtures in white-dwarf stars which, after ignition, become thermonuclear supernovae. This presentation describes the properties of the LTD transition using videos made from numerical solutions of the multidimensional, unsteady, chemically reacting, Navier-Stokes equations. The discussion focuses on selected features of the flow, including: formation of a turbulent flame and the nature of the turbulence, creation of hot spots as the origins of detonations, effects of stochastic processes on our ability to make predictions, and comparisons between simulations and experimental data.

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