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.