Marginal Separation

An analytical and numerical study is presented on the response of high Reynolds number flow when, starting from a fully attached state, it is forced to gradually approach separation as a certain critical parameter is increased. The end of attached flow near a rounded leading edge is the particular problem considered, although the application of the theory is much wider. The critical parameter is the angle of incidence. The Goldstein singularity first appears only weakly, and then the attached‐flow concept can even admit a small local separation bubble. As the singularity increases in strength, however, a solution of this type suddenly ceases to exist and a dramatic transition to another, separated form of motion seems to be implied. Nonuniqueness of the attached‐flow solution is also found.