Robust vortex control of a delta wing by distributed microelectromechanical-systems actuators

Micromachined actuators have be en used successfully to control leading-edg e vortices of a delta wing by manipulating the thin boundary layer before f low separation. In an earlier work (Lee, G. B., Ho, C. hi., Jiang, E, Liu, C., Tsao, T., and Tai, Y. C., "Distributed Flow Control by MEMS," American Society of Mechanical Engineers; International Mechanical Engineering and E xposition Nov. 1996), we demonstrated that small disturbances generated by these microactuators could alter large-scale vortex structures and conseque ntly generate appreciable aerodynamic moments along all three axes for flig ht control. In the current study, we explored the possibility of independen tly controlling these moments. Instead of using a linearly distributed arra y of microactuators covering the entire leading edge as done in the previou s study, we applied a shorter array of actuators located on either the forw ard or the rear half-section of the leading edge. Both one- and two-sided c ontrol configurations have also been investigated. Data showed that the pit ching moment could be generated independently by appropriate actuation of t he microactuators. To understand the interaction between the microactuators and leading-edge vortices, we conducted surface pressure distribution, dir ect force measurements, and flow visualization experiments. We investigated the effects of microactuators on the vortex structure, especially vortex c ore location. Experimental results showed that asymmetric vortex pairs were formed, which leads to the generation of significant torques in all three axes.