# Partial Oscillation Flow Control on Airfoil at Low Reynolds Numbers
## 5 Conclusions  
(1) The application of partial oscillation on the airfoil skin significantly enhances its aerodynamic attributes. Relative to a rigid airfoil configuration, the lift coefficient rises by 4.9%, the drag coefficient reduces by 15.3% and consequently, the lift-to-drag ratio escalates by 23.8% due to this oscillatory effect.  
(2) In comparison with a non-oscillating rigid airfoil, the pressure drag coefficient of the oscillating airfoil diminishes, whereas the viscous drag coefficient increases. As the oscillation frequency rises, the lift coefficient initially ascends but subsequently declines, while the drag coefficient first drops and then rises.  
(3) The chordwise position of the oscillating surface plays a pivotal role in influencing the airfoil's performance and flow field properties. The most advantageous placement for the partial oscillation surface is in proximity to the airfoil's leading edge and at the center of the LSB. Under such configurations, the partial oscillation effectively mitigates laminar separation over the airfoil, thereby improving its overall lift-to-drag performance characteristics.  
This study confines its investigation to two-dimensional analyses of localized oscillation on airfoil surfaces, inherently possessing certain limitations. Future endeavors will extend to explore flow control research involving the three-dimensional oscillation  
Figure 19: Shapes of LSB at different times in one oscillation cycle (\(P=0.6c\)). (**a**) \(t=0T\); (**b**) \(t=0.2T\); (**c**) \(t=0.4T\); (**d**) \(t=0.6T\); (**e**) \(t=0.8T\); (**f**) \(t=1.0T\).  
of wing surfaces. The intent is to delve deeper into the synergistic interactions between three-dimensional vortex formations, spanwise flow, wingtip vortices and wing surface oscillation under three-dimensional conditions, thereby advancing the understanding of these intricate dynamics. On the other hand, this paper conducts a study on the local oscillation of airfoils using numerical simulation methods. Nevertheless, experimental investigations into the local oscillation of the airfoil have not yet been undertaken, and thus, the numerical simulation outcomes regarding the local oscillation of the airfoil have not yet been validated through experimental verification. Future work will encompass an extended study into wind tunnel experiments on the local vibrations of airfoils, with the objective of validating their flow control efficacy.  
G.L.: conceptualization, methodology, writing--original draft. J.W.: data curation, writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Natural Science Foundation of China (grant number 12202297) and Sichuan Science and Technology Program (Project No. 2021 ZDZX0001, 2023 YFG0329).  
Not applicable.  
The data in this paper can be obtained from the corresponding authors according to reasonable requirements.  
We sincerely thank the Tianfu Engineer-oriented Numerical Simulation and Software Innovation Center of Sichuan University for providing the necessary computational resources and financial support for our research.  
The authors declare no conflicts of interest.