Project No. 2313

PRIORITY PROJECT

Primary Supervisor

Dr Jorn A Cheney – University of Southampton

Co-Supervisor(s)

Dr Neil Gostling – University of Southampton

Prof Bharath Ganapathisubramani – University of Southampton

Andy Philippide – University of Sussex

Summary

Is there a biological rule that requires all gliding mammals to share similar morphology and aerodynamics?

Gliding mammals have converged upon similar body plans no fewer than six times in the orders of Rodentia (rodents), Diprodontia (within marsupials), and Dermoptera (nearest relatives being primates). Each evolved a thin membrane of skin between the forelimb and hindlimb, which forms a low-aspect-ratio wing utilised to fly at high angles relative to the wind (angles of attack). These animals fly at angles of attack three-fold greater than expected, which results in unexpectedly low glide distances. Our project aims to test whether this repeated convergence toward unexpected aerodynamics results from a local optimum in flight performance due to a steep drop in performance caused by the aeromechanics of thin and compliant membrane wings. Specifically, at certain angles of attack, depending on wing geometry and material, membrane wings vibrate and create instability in control and performance which could act as an evolutionary barrier.

Students would first construct and measure the aerodynamic performance, membrane 3-D shape, and pitching behaviour of wings varying in aspect ratio and membrane thickness to map the evolutionary landscape of flight with membrane wings at high angles of attack. This fitness landscape will then be used in evolutionary simulations with varying conditions, to test whether, and under what simulated conditions, there is a point of convergence, or slowed evolutionary speed that could lead to temporary convergence.

This work will elucidate the evolution of flight in all mammals, which all fly using skin membranes with a tendency to vibrate; it may also lead to understanding the evolutionary restrictions placed upon bats, the only mammalian flapping-winged flier. Additionally, it will provide aerodynamic insights into two neglected aerodynamic domains: high-angle-of-attack flight, and low-aspect-ratio wings.

Ideal candidates will be interested in both biological and physical sciences.