Several physical and chemical phenomena invalidate the assumption of adiabatic flow in many compressible flow problems. When such processes are included in the mathematical model, the difficulties of calculation usually mask the important non-adiabatic nature of the flow. Hence, the effects of the variation of total temperature along the streamlines is often studied without direct reference to the mechanisms responsible for this behavior. These inviscid, non-conducting, steady flows with energy addition by heat sources are termed "diabatic" and correspond to heating processes which are thermodynamically reversible. The results from diabatic flow studies provide the basic insight into heat addition effects which is necessary before investigating more complicated problems where such phenomena as viscosity, conduction, diffusion, changes in gas composition, and electromagnetic effects are considered. Some fluid dynamics problems related to combustion processes and involving changes in total temperature were first formulated correctly in the independent work of Chapman [1] and Jouguet [2] at the early part of this century. In a later paper, with application to meteorology, Kiebel [3] gave a complete classification of viscous, compressible flow with energy addition into thirteen dynamically permissible categories. In spite of the early recognition of the importance of heating effects, the discipline of diabatic flow has essentially been developed since 1944. Only a few representative papers and those which are necessary to place this work in proper perspective with respect to past investigations will be discussed here, but a more complete summary of the existing literature on diabatic flow can be found elsewhere [4]. Compressible flow textbooks usually present only the fundamentals of one-dimensional "simple-heating", although Tsien [5] and Krzywoblocki [6] present discussions of some of the more general aspects of diabatic flow. Most of the basic ideas about the effects of heat addition on the flow properties, the behavior of the streamlines at the sonic condition, and the phenomenon of thermal choking were obtained from the early one-dimensional studies [7, 8, 9, 10]. It was established [11, 12, 13, 14] that the effects of localized heat sources are much like those of fluid sources. Such ideas led to the patent *