Parallel DNS of turbulent flames with detailed reaction schemes

Abstract

Direct numerical simulations (DNS) have become one of the most effective tools for the investigation of the fundamental processes apparent in turbulent combustion. Computational power is still a limiting factor in performing such DNS. A DNS code using detailed models for molecular transport and chemical reactions is presented, which is capable of making effective use of the computational power of massively parallel computers. This code has been used for an investigation of premixed and non-premixed hydrogen-air flames interacting with (initially) homogeneous decaying turbulence. A strong impact of the turbulence on the local heat release is observed in the case of the diffusion flames. The formation and burnout of isolated pockets is observed in the turbulent premixed flame. A flame normal analysis shows the laminar flamelet like structure of the main flame front as well as of the isolated pocket in the early stage of burnout. Nomenclature Ea = activation energy Eb,P = parallel efficiency E — turbulent energy eT = total energy h = specific enthalpy — wave number kd = wave number associated with maximum of dissipation ke = wave number associated with maximum of turbulent kinetic energy k = rate coefficient M = molar mass M = mean molar mass of the mixture Nr = number of elementary reactions Ns = number of chemical species p — pressure q = heat flux R = gas constant .Re A = Reynolds number based on integral length 56jp = parallel speedup s = flame normal coordinate T = temperature t = time u = velocity u = velocity component u' = turbulent velocity fluctuation V = diffusion velocity Y = mass fraction e = dissipation z/r) = stoichiometric coefficient of reactant Z/P) = stoichiometric coefficient of product