| dc.description.abstract | In this study, an experimental investigation was performed to characterize and validate three novel flow control strategies for unsteady aerodynamics. These three strategies are based on active and passive flow control designs. The two active control strategies make use of smart material alloy’s (SMA) located on the leading and trailing edge of a Boeing-Vertol VR-12 airfoil used in rotorcraft wings. The SMA used were macro fiber composites (MFC) a piezo-electric actuator. These actuators were located at the 25% and 85% of the chord length. Two different implementation strategies are used: one as an active morphing of the leading and trailing edge, second as acoustic resonators on the leading edge. The third strategy was of a passive flow control structure located on the pressure side of the leading edge of a NACA 0012 airfoil. This strategy makes use a microcavity to mitigate the transient separation and dynamic stall. In addition to the three novel strategies, traditional approaches such as drooping of the leading and trailing edge were studies. All systems were tested in both a static condition where the airfoil is held stationary as a freestream velocity is applied to the airfoil. As well as testing with a dynamic motion of the airfoil simulating a sinusoidal pitching motion. All of these tests were performed in the open loop wind tunnel located in the advanced flow diagnostics lab. The details of the wings design, manufacturing, actuation, programing, control, and test implementation is reported herein. The flow fields were measured through use of 2-D particle image velocimetry (PIV) an optical diagnostic flow methodology used for characterization and validation of the designs. To capture more detail of the unsteady and unpredictable nature of the flow, time resolved 2-D PIV, is implemented to provide full details of the flow while each strategy undergoes multiple pitching cycles. All three flow control strategies showed positive improvements to the airfoil performance. The active morphing provided the largest performance boost as the flow remained attached throughout the pitching experimentation. Showcasing the improvement that active morphing has over traditional methods of droop. The acoustic resonance was a close follow-up showing improvement in both pitching and static conditions, however for the case of pitching the system was inconsistent. This has been attributed to the need to adjust the frequency generated while the angle of attack changes. Lastly the passive cavity structure showed limited improvement during light dynamic stall, improving the flow when compared to the baseline. However, the flow conditions needed to concisely prove the control strategy were not possible with the current equipment. | en_US |
