A Study of The Aerodynamics of Butterfly-type Flapping Wing
Date Issued
2012
Date
2012
Author(s)
Chang, Ya-Han
Abstract
Corresponding to the requirements of applications and tasks, the size of the unmanned aerial vehicles (UAVs) is tending smaller and smaller. Following the size reduce, the aspect ratio of the UAV wings reduces as well. Consequently, the common fixed-wings are no longer capable of providing enough aerodynamic forces against the gravity. In the nature, insects’ wings have low aspect ratios, but they fly freely in the air. Their physical characteristics and movement patterns must have implications which are useful for developing micro UAVs. This study aimed at the flow fields induced by a swallowtail butterfly in use of the software “ANSYS Fluent.” Parameters such as the flapping frequency, the angle of attack, the wing shape, and the swallowtail effect were explored. The simulation results show: when a swallowtail butterfly-type wing is in gliding, its lift force increases with the angle of attack first but decreases later, peaking at an angle of 40˚. On the other hand, the drag force increases monotonically. Consequently, the lift-drag ratio has its maximum value when the angle of attack is 10˚. The flapping flight has similar variation trends in the average lift force, drag force and the lift-drag ratio to the gliding flight but the magnitudes increase with the flapping frequency. Furthermore, unlike the long flat-panel wing, the butterfly-type wing can seemingly produce a positive pitch moment to rotate its body and consequently increase the angle of attack during the downstroke motion by taking advantage of its forward-swept leading edge. A negative pitch moment is generated during the upstroke motion the other way round. Similar observation had been reported in the literature. Through the 3D-streamline visualizations, it was also found that the swallowtail can help building some solid flow structures in the neighborhood during the downstroke motion when the flapping frequency is high, regardless of the angle of attack. It is believed that these structures are related to the flow field stability.
Subjects
Swallowtail butterfly
Flapping flight
Aspect ratio
Micro aerial vehicles
Type
thesis
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