Recent interest in developing micro air vehicles (MAVs) for a variety of both civil and military uses has driven significant research into the aerodynamics of natural flyers, such as insects, birds and bats. Insects, in particular, exhibit desirable flight characteristics that MAV designers wish to incorporate into their designs, however our understanding of how these animals fly is still limited. Research into insect flight has shown that they employ a number of unsteady mechanisms, the most

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... evalent of these being the formation of a leading-edge vortex (LEV) which provides the wing with enhanced lift. While this research has greatly improved our understanding of insect flight, the effect of the wing's shape on these unsteady mechanisms is not well understood. This thesis describes an investigation into the effect of two wing morphological parameters, aspect ratio and camber, on the flow structures around flapping and rotating wings in an insect-like flight regime. The effect of wing aspect ratio is first explored at different Reynolds numbers using a numerical model of an altered fruit fly wing revolving at a constant angular velocity. Increasing the Reynolds number for an aspect ratio of 2.91 resulted in the development of a dual LEV structure, however increasing aspect ratio at a fixed Reynolds number generated the same flow structures. This result shows that the effects of Reynolds number and aspect ratio are linked. An alternate flow scaling method, using the wing span as the characteristic length, is presented to decouple the effects of Reynolds number from those of aspect ratio. This resulted in a span-based Reynolds number, which can be used to independently describe the development of the LEV. Indeed, universal behaviour was found for various parameters using this scaling. The effect of aspect ratio on the vortex structures was then assessed at different span-based Reynolds numbers and it was found the wing aspect ratio had the effect of shortening the wing's chord length relative to a fixed LEV size. [...]