The structure and behaviour of separation bubbles

Abstract

Summary. A study has been made of laminar separation bubbles formed over a wide range of Reynolds numbers and in a variety of pressure distributions. The structure of the bubble depended on the value of the Reynolds number of the separating boundary layer and a parameter based on the pressure rise over the region occupied by the bubble. Conditions for the bursting of \\'short\\' bubbles were determined by a unique relationship between these two parameters. Hot-wire measurements of both mean and fluctuating velocity in the separated region, together with oscilloscope records of the fluctuations, explain some of the flow mechanisms involved.