Science
Local, Small-Scale Interaction of Turbulence with Chemical Reactions in H2-O2 Combustion
1994 Volume 14 Issue 1+2 Pages 1-18
Details
1994 Volume 14 Issue 1+2 Pages 1-18
A brief survey of commonly used techniques for simulating turbulent combustion is presented, and it is noted that, except for direct numerical simulation (which is too computationally intensive even on foreseeable supercomputers), none of the current methods is able to predict details of chemical kinetics/turbulence interactions. A new approach, based on an extension of earlier work with one-dimensional mathematical models of turbulence by McDonough and co-workers (1984a, b, 1986, 1989), is applied to study a simple, single-step forward reaction H2-O2 combustion problem. The method requires no averaging, or modeling, at any level due to an additive multi-scale decomposition of governing equations. Thus, like direct numerical simulation, it is completely consistent with the original, unaveraged equations; but required arithmetic is significantly reduced via consistent linking of large-scale and small-scale phenomena, resulting in the ability to focus on local regions and consistently (with respect to the full equations) simulate phenomena within these regions to a high degree of accuracy. In addition, the method is naturally parallelizable at several algorithmic levels. This technique, termed additive turbulent decomposition, is treated theoretically, and then applied to the one-dimensional, viscous, compressible Navier-Stokes and species equations. Preliminary computational results showing detailed chemical kinetics/turbulence interactions at the tip of an H2-O2 diffusion flame are presented and discussed for a flow with Reynolds number 6000, and thermal and mass diffusion Peclet numbers of 1000 and 3000, respectively. Computed results show a relatively long period of increase in negative amplitude of H2 and O2 concentrations followed by onset of chaotic oscillations simultaneously in velocity and temperature. Corresponding fluctuations then begin to appear in the concentrations via feedback from advective and species production terms.
