LOCAL AND GLOBAL INSTABILITY PROPERTIES OF SEPARATION-BUBBLES

A family of velocity profiles with reversed flow, typical of those fou nd in separated flows, are examined for their linear instability prope rties. Specifically, a family of modified Falkner-Skan profiles are an alyzed for the onset of absolute instability as the magnitude of the r eversed flow increases. The mode of instability associated with the in flection 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 u sed to construct generic models of separation bubble and study the pos sible onset of global instability in the representative spatially-deve loping flows. (C) Elsevier, Paris.