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Investigation of a Pitching Airfoil under Stall Flutter Conditions with an Energy Harvesting Approach

Sedaaghi, Reza | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58682 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Ebrahimi, Abbas
  7. Abstract:
  8. This dissertation presents an experimental study on the direct conversion of the aeroelastic phenomenon of flutter stall into electrical energy. A NACA 0015 airfoil with one torsional degree of freedom was coupled to an electrical power generator, and the system’s performance was systematically evaluated through simultaneous characterization of aerodynamic power and electrical output power. The experiments were conducted on a one-degree-of-freedom test rig in a wind tunnel. The research was carried out within the Reynolds number range of 6×10⁴ to 1.6×10⁵, examining the effects of key parameters including free-stream velocity, initial angle of attack, torsional stiffness, and elastic axis position. Their influence on the amplitude and fundamental frequency of limit-cycle oscillations, the hysteresis loops of the torsional moment coefficient, the extractable aerodynamic power, and the electrical output power was investigated. The results identified downstream displacement of the elastic axis from 0.25c to 0.33c as the most significant variable, increasing aerodynamic power by up to 107%. Moreover, the transition from asymmetric to symmetric limit-cycle oscillations led to a 176% increase in aerodynamic power. This phenomenon is associated with the transition from “weak” to “deep” dynamic stall, and analysis of torsional moment hysteresis loops confirmed that symmetric, three-subloop patterns of torsional moment produce the highest aerodynamic power
  9. Keywords:
  10. Energy Harvesting ; Stall Flutter ; Dynamic Stall ; Limit Cycle Oscillation ; Pitching Airfoil ; NACA 0015 Airfoil

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