Challenges in Turbulent Mixing with Combustion

Turbulent combustion combines the complexities of turbulence and mixing, challenges not met in the twentieth century, with the complexity and subtlety of chemical kinetics. This discussion focuses on progress and some turbulent-mixing issues in chemically reacting flows stemming from experimental, modeling, and direct-numerical simulation (DNS) studies. The mixing transition will be discussed. DNS studies of the Rayleigh-Taylor instability in miscible fluids reveal an early-time diffusive growth and a strong sensitivity to initial conditions. Recent experiments address the assumption of isotropy in turbulence and mixing. Experiments in high-speed shear layers elucidate some effects of compressibility on the mixed-fluid field. Issues involving molecular-transport coefficients will also be discussed.