# Study of Airfoil Deflections for Unsteady Aerodynamics Optimization in Pitching Airfoils +
## 4 Conclusions  
Four versions of the Boeing-Vertiol VR-12 wings having leading edge and trailing edge deflections were designed, fabricated, and tested. Numerical simulations and particle image velocimetry were used to assess the basic performance of the deflected airfoils as a proof of concept of the functionality with pitching and tandem configurations. The wings were fabricated with an interior to produce a light-weight and robust wing to withstand pitching and aerodynamic conditions in a wind tunnel. Numerical simulations determined the initial geometry parameters to be implemented and studied from the aerodynamics benefits of the deflections in terms of lift and drag as a function of angle of attack. The aerodynamic designs utilized these initial CFD assessments and were then proven using PIV phase-averaged techniques in the wind tunnel. The conditions of this study were a Reynolds number of 250,000 and pitching frequency of 4.8 Hz (reduced frequency of 0.04), representing a medium regime of rotorcraft operations. Linear tandem tests with two in-phase or out-of-phase pitching wings with centers of pressure separated by three and a quarter chord length were also performed to simulate unsteady wing-wing interactions and test the deflection performances. Three separate test methods were performed for the deflected models, the singular pitching airfoil and in-phase and out-of-phase tandem pitching. Comparing results, it was found that the wing with leading edge deflection had significant benefits over the baseline and the trailing edge deflected wings, including dynamic stall mitigation for certain angles of attack during pitching with separation region sizes and origin measured from the PIV fields. The study puts forward the initial conditions towards producing a fully dynamic morphing airfoil.  
Conceptualization, W.R., J.E., T.S. and Y.B.S.; methodology, W.R., J.E., T.S., and Y.B.S.; software, T.S. and Y.B.S.; validation, W.R., J.E. and C.F.; formal analysis, W.R., J.E., C.F., T.S. and Y.B.S.; investigation, W.R., J.E., T.S. and Y.B.S.; resources, W.R., J.E. and Y.B.S.; data curation, J.E., T.S. and Y.B.S.; writing--original draft preparation, W.R., J.E., T.S. and Y.B.S.; writing--review and editing, W.R., J.E., T.S., C.F. and Y.B.S.; visualization, W.R., J.E. and C.F.; supervision, J.E. and Y.B.S.; project administration, J.E.; funding acquisition, J.E. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Department of the Navy Science and Technology Office of Naval Research. Aerospace Science Research (grant No. N00014-20-S-B001) under Program Officer Dr. [PERSON] made this research project possible.  
Not applicable.  
Data Availability Statement: Data are available from the authors upon request.  
The authors thank [PERSON] and [PERSON] from the NDSU Department of Mechanical Engineering for their advice, machining and fabrication of various necessary components and airfoils. The NDSU Department of Mechanical Engineering is also acknowledged for additional resources and financial support.  
The authors declare no conflicts of interest.