The response of a laminar separation bubble to ?aircraft engine representative? freestream disturbances

Abstract

This paper investigates a large, laminar separation bubble that extends from near the leading edge and along the pressure surface of a low-pressure turbine blade. Whilst stability analyses are not performed, experiments suggest that the separation is convectively unstable at positive incidence. The separation then appears to exhibit absolute instability and, finally, global instability as the incidence of the blade becomes more negative. The conjectured onset of absolute and global instability is used to provide a possible explanation for the separation’s reduced sensitivity to ‘aircraft engine representative’ disturbances as the incidence of the blade becomes more negative.