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- Type of Document: Ph.D. Dissertation
- Language: Farsi
- Document No: 55478 (45)
- University: Sharif University of Technology
- Department: Industrial Engineering
- Advisor(s): Ebrahimi, Abbas
- Abstract:
- Increasing the kinetic energy of the near-wall fluid by exciting shear layers is known as an effective method for flow separation control. So far, choosing the proper approach to apply excitations has been a challenging issue in the field of flow control. This work investigates flow control of airfoils in static stall and flutter conditions, employing shear layer excitation technique and plasma actuators. This research introduces a novel flow separation control, namely dual-point excitation of shear layers and compares its performance with the conventional single-point excitation method. Two airfoils (NACA 4415 and NACA 0015) have been considered as the baseline test-cases. In the first part of this research, large eddy simulation was used to examine the feasibility of dual-point excitation technique in static stall control. PSD and DMD analyses were utilized to identify turbulent flow structures among the wake and the effect of the proposed control method on the flow field was determined. In the second part of this research, the effectiveness of dual-point excitation technique in controlling static stall was examined through wind tunnel testing. In addition, the effect of different excitation frequencies on the aerodynamic performance of proposed flow control method was studied considering the airfoil surface pressure scans. The last part of the research investigated the potential of using dual-point excitation technique to modify stall flutter oscillations of an airfoil. Wind tunnel experiments were performed, using a test-rig that provides an elastic degree of freedom in pitch. In this part, the effect of excitation frequency on the airfoil pitching moment and aerodynamic damping was identified. According to the first and second parts of this work, dual-point excitation method has promising performance compared to single-point excitation. In Addition, it was shown that excitation with a frequency of twice that of the natural vortex shedding has the most influence on enhancing L/D parameter. Finally, the third part of the research indicated that applying dual-point excitation to the airfoil in stall flutter oscillations delays dynamic stall process and advances flow reattachment.
- Keywords:
- Stall Control ; Wind Tunnel ; Plasma Actuator ; Shear Layer ; Dual-Point Excitation ; NACA 0015 Airfoil ; Large Eddy Simulation (LES)
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