Detection of Boundary Layer Separation and Implementation of Autonomous Vortex Generators

Boundary layer separation is a physical phenomenon that can result in aircraft stall, which is responsible for many fatal airplane accidents. This research aims at designing a boundary layer separation detection system that could be added on new aircraft or retrofitted on existing aircraft. This detection system was designed, fabricated, and used to demonstrate an autonomous vortex generator system that detects boundary layer separation in real-time and activates vortex generators to delay the boundary layer separation. The system uses flush-mounted microphones to detect an increase of acoustic power in the low-frequency range of pressure fluctuations indicating incipient separation. Vane-type vortex generators are aligned with the flow until the microphones detect separation. The vortex generators are then rotated to an angle of attack at which they produce vortices that delay boundary layer separation. Wind tunnel tests are performed with a 2D wing with aNACA0012 airfoil at chord Reynolds numbers of 500,000 and 1,000,000 in order to characterize the boundary layer’s frequency domain over a range of angle of attack that includes stall. Results show that the microphones are effective at detecting boundary layer separation and can be used to activate vortex generators. The active vortex generators are shown to increase maximum CL 13.8% and 6.9% for Reynolds numbers of 500,000 and 1,000,000 respectively when compared to maximum CL of the clean wing.