Aerodynamics, Wing Biomechanics, and the Evolutionary Diversification of the Chiroptera

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Swartz 9723736 The origin and elaboration of evolutionary novelty comprise one of the most fundamental areas of evolutionary inquiry. In this light, the structure of vertebrate wings, their derivation, and their function during flight have attracted the attention of biologists and engineers for many years. However, the accurate estimation of the forces developed within the structural components of the wing, and the full understanding of the mechanical, aerodynamic, and energetic significance of the wing form and wing movement patterns have been neglected. As a consequence, knowledge of the evolutionary origins and history of diversification of flight apparatus remains primitive In this study, we will model the flight of a large bat to analyze aerodynamics, mechanics, and energetics. A bat has been selected as our study organism because bats are characterized by an anatomical organization (rigid bony elements interconnected by an elastic wing membrane) that is relatively simple to model in a biologically realistic fashion. The PI will the use our computer simulation to ask: 1) what are the magnitudes of the joint forces and moments in the wing during flight? how large are the skin and bone stresses developed within the wing?; 2) how do small-scale variations in wing morphology and kinematics affect the joint forces and moments and the skin and bone stresses developed within the wing? 3) what features of wing morphology and kinematics affect the maneuverability, structural stability and aerodynamic performance of the wing, and the mechanical power of flight? These questions will be answered by accomplishing a series of interrelated objectives. A mechanically and biologically realistic computer model of a flying bat will be developed, based on Pteropus poliocephalus, the gray-headed flying fox, a species from which a great deal of functional and anatomical information has already been obtained. Inputs into the model will include anatomical information, dat a concerning the mechanical properties of wing tissues, and three-dimensional descriptions of the movement patterns of the wing. A detailed computer model will be constructed, and then used to generate information about the forces developed at the wing joints, the stresses in the wing bones and skin, the mechanical power of flight, the ability of the bones to withstand buckling, and the stability and maneuverability of the wing. Sensitivity analyses will be carried out to determine the relative influence of body size, wing shape, flight speed, and biomechanical properties on the model outputs. The results of this study will be able to serve as the foundation for future studies concerning the origin, diversity, and adaptation of flight among bats.