Interaction of a shock with a sinusoidally perturbed flame

The interaction of a shock wave and a sinusoidally perturbed premixed flame was studied by solving the reactive Navier-Stokes equations with flame front resolved. An idealized chemical model was used that reproduces the combustion properties of a stoichiometric acetylene-air mixture. The interaction increases the surface area of the flame and the energy release in the system. The increase in energy release is due to two effects: the increase in surface area and the increase in the density of the compressed material. The timescale of the growth of the energy release is the Richtmyer-Meshkov characteristic timescale. The interaction creates vorticity, and the vortices act to maintain a high level of energy release long after the shock wave has passed through the flame. The strength of this vorticity is not enough to stretch and locally extinguish the flame. Three-dimensional perturbations of the same amplitude and wavelength grow a factor of similar or equal to 2 faster than the two-dimensional perturbations, and the maximum energy release rate is a factor of similar or equal to 2 larger. The calculations show that the maximum increase in the energy generation rate due to a single interaction of a shock and a flame does not exceed a factor of 20 to 30. To greatly increase the burning rate, multiple shock-flame interactions are required. (C) 1998 by The Combustion Institute.