BISHOP, K.L.; Brown University: A physical modelling approach for determining the effect of shape on the aerodynamic forces generated by a flexible wing.

Although it is generally accepted that bats evolved from arboreal gliders, there is an implicit assumption in the literature that gliding and flapping flight represent two separate adaptive zones. It is also commonly assumed in the literature that typical mammalian gliding membranes are not effective flapping wings and that typical bat wings are not effective gliding membranes, suggesting that there is no functional continuity between these two locomotor modes. To begin to address the question of functional continuity across this morphospace, I test the assumption that wings with a more bat-like morphology have poorer gliding performance than wings with a more glider-like morphology. In this study, better performance is defined as having a higher lift to drag ratio, which results in a lower glide angle, thus a longer glide distance for a given vertical drop. To do this, I have built physical models of differently shaped wings with an elastic wing membrane, spanning a plausible morphological series from a more glider-like to a more bat-like shape. I then measured the lift and drag forces on these models in a wind tunnel at a wide range of speeds and angles of attack. This study combined with further studies using flapping wing models will help to clarify whether a gliding to flapping transition is physically possible in mammals.