1. '!'½regrowing body of literature on hypersonic lee-surface flow fields has still not resolved many of the questions that are critical to a fundamental understanding of the flow. The dominant role of vortices in tbe development of the flow field has been examined for a variety of geometric configurations, but there are inconsi.stencies in these accounts which need to be rectified. Many of the studies of lee-surface phenomena have assumed an over-simplified modeling of the flow which cannot' explain-much of the data; for example, most analyses postulate a conical lee-surface flow field whereas recent work has clearly indicated that the viscous interaction can invalidate this assumption(l]-[3),t A correct interpretation of the flow and an assessment of such variables as angle of attack and Reynolds number is imperative because the vortices induce potentially serious heating to the upper surfaces of hypersonic configurations. One of the objectives of th'ls report is to provide a unified analysis of the vortex phenomenon at high speeds by dravins on the commonfeatures observed experimentally on different geometries. The present study *Aerospace Engineers, Configur,ition Flow Fields Section, Hyµcrsonic Vehicles Division. **Resident Rcsearch Associate, Confirri.u-ation Flow Fields Section, Hypcr 5onic Vehicles Division (on let:l.vc