Local and global instability properties of separation bubbles

A family of velocity profiles with reversed flow, typical of those found in separated flows, are examined for their linear instability properties. Specifically, a family of modified Falkner-Skan profiles are analyzed for the onset of absolute instability as the magnitude of the reversed flow increases. The mode of instability associated with the inflection point in the vicinity of the dividing streamline is found to become absolutely unstable as the peak reversed flow approaches about thirty percent of the free stream value. The family of profiles were used to construct generic models of separation bubble and study the possible onset of global instability in the representative spatially-developing flows. (C) Elsevier, Paris.