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Aerodynamic Investigation of an Aeroelastic Flapping Wing and Optimum Design Method

Ebrahimi, Abbas | 2011

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 41945 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Mazaheri, Karim
  7. Abstract:
  8. Flapping wing vehicles produce aerodynamic lift and thrust through the flapping motion of their wings. The dynamic performance of a flexible membrane flapping wing is experimentally investigated here. To investigate aeroelastic effects of flexible wings (specifically, wing’s twisting stiffness) on hovering and cruising aerodynamic performance, a flapping-wing system and an experimental setup were designed and built. This system measures the unsteady aerodynamic and inertial forces, power usage and angular speed of the flapping wing motion for different flapping frequencies, angles of attack, various wind tunnel velocities up to 12 m/s and for various wings with different chordwise flexibility. Aerodynamic performance of the vehicle for both no wind (hovering) and cruise condition was investigated. Results show how elastic deformations caused by interaction of inertial and aerodynamic forces with the flexible structure may affect specific power consumption. A new scheme for finding flight envelops for a special flapping vehicle is introduced as well. For each given weight (or payload), one may find the best cruise speed for maximum range, corresponding to minimum ratio of power to cruise speed (i.e., energy usage for unit distance), or for maximum endurance corresponding to minimum power (i.e., minimum flapping frequency).
    Also, in this thesis the dynamic formulation of the equations of motion of flexible wing that undergo large rotational displacements as a rigid body flapping motion are developed using the floating frame of reference formulation. The structural dynamic model contains rigid body motion, flap-wise bending and torsional elastic deformations. The Lagrange approach is utilized in deriving the dynamic equations of motion for the total flexible flapping wing system with specified trajectory. Approximation method is used to modeling the elastic deformations of flapping wing system by assuming that the shape of deformation of the body can be predicted using finite set of known functions. The equations of motion become nonlinear in the deformation degrees of freedom due to inertial coupling between the rotation and the deformation of the body
  9. Keywords:
  10. Flexible Wing ; Aeroelasticity ; Flapping Wing ; Aerodynamic Performance

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