ABSTRACT
As we noted in Table 1.1, the variations possible in the density of a flowing fluid lead to one of the main divisions common in the study of fluid mechanics. In this part we put aside any detailed treatment of other complicating factors such as intricate geometries and/or viscous effects. Limits on geometric variations will be imposed by the one-dimensional constraint and, when viscous effects are taken into account, only cases of constant-area internal flows will be considered. These simplifications will not impede the main goals of Part Two, which are to demonstrate the effects of variable density and to present some of the standard methods for analyzing flows in which density variations play a significant role. We begin with a description of the assumptions that form a foundation for the subsequent developments.
