Gaseous diffusion flames: simple structures and their interaction

This is a synoptic overview of a selection of works dealing with single dif fusive structures, with their mutual interaction in simple flows and their statistical modeling in complex flows. The focus is on reacting conditions pertaining to gaseous diffusion flames, but isothermal structures are also described when they are of some conceptual interest. This paper considers o nly few representative works for each subject, which are functional in expl aining the key characteristics of the diffusive structures. The extension, given to single subjects, is not weighed according to the number of related publications but on the relevance to the basic understanding of the genera l framework concerning diffusion flames. One-dimensional structures are fir st discussed. They are ordered according to the number of balance equation terms needed for their description. Two-dimensional (2D) structures are the n introduced following an order based on their convolution level. Some pion eering work on three-dimensional structures is further quoted. The temporal evolution of simple structures in quiescent or simple flowing 2D systems i s considered. The latter case is exploited to present classification of dif fusion-controlled mixing regimes. Modeling characterization approach of tur bulent diffusion flames is also described in order to yield a self-sufficie nt didactic presentation. The approach based on the flame surface density m odel is specifically discussed because of its potential use in the determin ation of qualitative and quantitative features of simple diffusion flames. (C) 2001 Elsevier Science Ltd. All rights reserved.