Retained Lift: Theoretical Difficulties With the Concept and an Alternative Explanation of Observations

Despite its broad acceptance, the present authors have come to believe that there are serious theoretical difficulties with the retained-lift concept. These difficulties were outlined by Yaras et al. (1992), who also presented an alternative explanation for the experimental observations. The title of this paper, however, reflected its broader content and the relatively brief comments regarding retained lift understandably attracted little attention. The present note contains a more thorough discussion of the theoretical considerations, which indicate that the retained-lift concept is invalid. It also contains an alternative physical explanation of why measured streamwise circulation is less than the bound circulation for typical tip clearances.