Turbulent Transport Properties of Wrinkled Flames

Abstract

Direct numerical simulation of a turbulent premixed flame with a single-step irreversible Arrhenius-type reaction is performed at u′/u L = 0.88, l t /δ = 15.9 and ρ u /ρ b = 7.53, and turbulent transport properties are evaluated. A fully developed stationary wrinkled flame is obtained in a domain of 8 mm × 4 mm × 4 mm. Turbulent fluctuations generally increase in the flame region, but streamwise component increases more than transversal components. This results in the generation of anisotropic turbulence in the flame region. Analysis based on the Favre-averaged transport equation of turbulent kinetic energy shows that pressure gradient term and pressure work term increase turbulent kinetic energy in the flame region, while diffusion and dissipation term and velocity gradient term decrease it in the flame region. The counter-gradient diffusion dominates turbulent scalar flux in the DNS data, and the BML model well predicts it. Analysis based on the Favre-averaged transport equation of turbulent scalar flux shows that mean pressure gradient term, velocity-reaction rate correlation term and fluctuating pressure term play important roles on production of counter-gradient diffusion, while mean velocity gradient term, mean progress variable gradient term and dissipation terms suppress it.