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Elaine S. Oran Thursday April 19, 4:30 PM | Research 1 Room 301 The transition from a subsonic turbulent flame to a supersonic reaction wave called a detonation, called the deflagration-to-detonation transition or DDT, is a dynamic process involving deflagrations, turbulence, shocks waves, and boundary layers. Because of the unsteady nature of DDT and the wide range of spatial and temporal scales involved, experimental diagnostics of DDT are difficult and extremely costly to make, and dare difficult and expensive to perform. DDT has been called one of the major unsolved problems in combustion and detonation theory. DDT has important practical consequences. For example, it continues to be the cause of severe damage in mines, chemical plants, and explosive storage containers. DDT is a fundamental in igniting explosives: it can start in very small gas-filled channels in granular energetic materials. Knowing whether and how DDT occurs in Type Ia (thermonuclear) supernovae is extremely important in astrophysics and cosmology for understanding the element abundance and determining the age, size, and curvature of the universe. This presentation summarizes results from series of multidimensional numerical simulations used to investigate the effects preceding and causing DDT. The reactive Navier-Stokes equations were solved on an locally adaptive mesh that resolves selected features of the flow, including the structure of the laminar flame. Applications of the results to chemical micropropulsion, safety in hydrogen storage, and Type Ia supernova explosions will be discussed. |