Date of Award
Doctor of Philosophy (PhD)
Mechanical and Aerospace Engineering
Micro air vehicles--Wings., Wings (Anatomy)--Aerodynamics., Animal flight.
Animal wings deform significantly during flight. However, the aerodynamic features of flexible wings interacting with the surrounding fluid have not been adequately explored. One of the main challenges in predicting aerodynamic forces is that the wing shape and motion are a priori unknown. In this dissertation, two-way coupled analytical fluid-structure interaction models for chordwise and spanwise flexible flapping wings in forward flight are derived. The unsteady aeroelasticity is modeled with the Euler-Bernoulli beam and Theodorsen equations under the small deformation assumption. The two-way coupling for a chordwise flexible airfoil is realized by considering the trailing-edge deformation relative to the leading-edge as passive pitch, affecting the unsteady aerodynamics. The spanwise flexible wing model considers transverse displacement as an effective plunge under the dynamic balance of wing inertia, elastic restoring force, and aerodynamic force. The aeroelastic response of both models agrees well with the high-fidelity numerical and experimental results. A novel aeroelastic frequency ratio is derived, which scales with the wing deformation, lift, and thrust for a chordwise flexible airfoil. The propulsive efficiency of the chordwise flexible airfoil strongly correlates with the amplitude of relative wing deformation. The spanwise flexible wing model suggests that the wing aspect ratio of the abstracted passerine and goose models corresponds to the optimal aeroelastic response. At these optimal aspect ratios, the flapping frequency is near the first spanwise natural frequency of the wing, suggesting that these birds may benefit from resonance to generate thrust. These analytical models can help further the understanding of biological locomotion and will be valuable for modeling and analysis of the dynamics, stability, and control of flapping flyers.
Kodali, Deepa, "Analytical aeroelastic models for chordwise and spanwise flexible flapping wings in forward flight" (2019). Dissertations. 194.