Supercritical (and subcritical) fluid behavior and modeling: drops, streams, shear and mixing layers, jets and sprays

A critical review of recent investigations in the realm of supercritical (and subcritical) fluid behavior is presented with the goal of obtaining a perspective on the peculiarities of high pressure observations. Experiments with drops, isolated or in groups, streams, shear and mixing layers, jets and sprays are tabulated and discussed as a precursor to forming a conceptual picture of fluid comportment. The physics of fluid behavior in the supercritical and subcritical regimes is discussed, and major differences between the observations in these two regimes are identified and explained. A variety of supercritical fluid models is then examined in the context of drop studies, and salient aspects of fluid behavior are identified. In particular, a model that has been validated with microgravity drop experiments is described and summarized; in this validated model, the differences in subcritical/supercritical comportment are interpreted in terms of lengths scales and it is this difference that is responsible for the traditional Lewis number expression no longer portraying the ratio of heat to mass transfer in supercritical fluids; instead, an effective Lewis number is recommended that gives a realistic estimate of the ratio of these length scales. Furthermore, the application of various fluid models to the description of supercritical fluid in various geometric configurations is discussed for conditions relevant to liquid rocket, Diesel and gas turbine engines. Such preliminary simulations performed with the validated fluid model have already reproduced some specific experimental features of supercritical fluid jet disintegration. Finally, comments are offered regarding future areas of research.