Micro air vehicles (MAVs) are operate in the size region under the same environmental conditions as natural flyers. Insects are a prime target for bioinspired designs of MAVs, as their wingroot fixed musculature is simpler than the flight muscles of birds and bats. Dragonflies are highly aerobatic insects having high aspect ratio wings in tandem; they control individual wings to utilize wake elements of the forewings by their hindwings. This thesis contains my effort to characterize the unique interactions between the wings of dragonflies. I use a spanwise resolved approach to address the gradual change of wing geometric relations in the root fixed flapping wing system. With the use of in-vivo flow measurements two characteristic regions with distinct flow features, and two transient re...[ Read more ]

Micro air vehicles (MAVs) are operate in the size region under the same environmental conditions as natural flyers. Insects are a prime target for bioinspired designs of MAVs, as their wingroot fixed musculature is simpler than the flight muscles of birds and bats. Dragonflies are highly aerobatic insects having high aspect ratio wings in tandem; they control individual wings to utilize wake elements of the forewings by their hindwings. This thesis contains my effort to characterize the unique interactions between the wings of dragonflies. I use a spanwise resolved approach to address the gradual change of wing geometric relations in the root fixed flapping wing system. With the use of in-vivo flow measurements two characteristic regions with distinct flow features, and two transient regions delimiting these, were identified. The dimensionless arc length was introduced to describe the effect of interaction in the wings spanwise direction. This parameter includes not only the phasing relations of the wings, but the ventral or dorsal shift in a wing’s flapping, thus it is more generally applicable. Additionally, the flight direction was found to affect the inter-wing interactions.

Secondly, a multilayer wing is proposed that generates lift with simple flapping motion. The wing takes up a different shape during the downstroke and during the upstroke; that mimics the asymmetric wing pitching of dragonflies. The wing generates an additional trailing edge vortex between its layers during upstroke that can boost thrust. The characteristic parameter defining the performance of the double layer wing is the difference between the dynamic shape deformation during the upstroke and the downstroke. It relates to the ratio of the chord length of the wing’s layers. A chord ratio of 0.5 resulted in the best performance.

I hope that my work will inspire further scientific research on dragonflies as well as MAV engineering.