'One-dimensional turbulence' simulation of turbulent jet diffusion flames: Model formulation and illustrative applications

A novel modeling approach to the simulation of turbulent jet diffusion flames based on the One-Dimensional Turbulence (ODT) model is presented. The approach is based on the mechanistic distinction between molecular processes (reaction and diffusion), implemented by the direct solution of unsteady boundary-layer reaction-diffusion equations, and turbulent advection in a time-resolved simulation on a 1D domain. The 1D domain corresponds to a direction transverse to the mean Row of the jet. Temporal simulations of jet diffusion flames are performed to illustrate the model's predictions of turbulence-chemistry interactions in jet diffusion flames. ODT predictions of flow entrainment, finite-rate chemistry and differential diffusion effects are investigated in hydrogen-air diffusion flames at two Reynolds numbers. Two-dimensional renderings of stirring events from a single realization show that ODT reproduces a number of salient features of simple developing turbulent shear flows that reflect the growth of the boundary layer and the mechanisms of turbulence cascade and spatial intermittency. Multiple realizations of jet simulations are used to compute axial and conditional statistics of streamwise velocity, major species, NO, and temperature. Comparison with experimental measurements indicates that chemical properties of interest can be captured by a model that involves a simplified representation of the flow structure. The results show, strong differential diffusion effects in the near field, with attenuation farther downstream. (C) 2001 by The Combustion Institute.