Investigation of passive flow control techniques to enhance the stall characteristics of a microlight aircraft

Abstract

This report investigates the enhancement of aerodynamic stall characteristics of a Skyranger microlight aircraft by the use of passive flow control techniques, namely vortex generators and turbulators. Each flow control device is designed and scaled to application conditions. Force balance measurements and surface oil flow visualisation are carried out on a half-model of the microlight to further investigate the nature of the flow on the aircraft with and without the flow control devices. The results indicate a clear advantage to the use of turbulators compared with vortex generators. Turbulators increased the maximum lift coefficient by 2.8%, delayed the onset of stall by increasing the critical angle by 17.6% and reduced the drag penalty at both lower (pre-stall) and higher angles of attack by 8% compared to vortex generators. With vortex generators applied, the results indicated a delayed stall with an increase in the critical angle by 2% and a reduced drag penalty at higher angles of attack.