Numerical simulation of deflagration-to-detonation transition: The role ofshock-flame interactions in turbulent flames

Two-dimensional reactive Navier-Stokes equations for an acetylene-air mixtu re are solved numerically to simulate the interaction of a shock wave and a n expanding flame front, the formation of a flame brush, and deflagration-t o-detonation transition (DDT). The effects of viscosity, thermal conduction , molecular diffusion, and chemical reactions are included. A new method fo r adaptive mesh refinement was used to ensure that the structure of the fla me front was resolved. The shock-flame interactions, through the Richtmyer- Meshkov instability, create and maintain a highly turbulent flame brush. Th e turbulence is not Kolmogorov turbulence, but it is driven at all scales b y repeated shock-flame interactions. Pressure fluctuations generated in the region of the turbulent flame brush create, in turn, hot spots in unreacte d material. These hot spots may then transition to DDT through the gradient mechanism. Repeated shock-flame interactions and merging shocks in unreact ed material lead to the development of a high-speed shock that moves out in front of the turbulent flame. The region between this shock and the flame is subject to intense fluctuations generated in the flame. The simulations show that the interactions of shocks and flames create the conditions under which deflagration-to-detonation transition may occur. (C) 1999 by The Com bustion Institute.