Bubble Burst Control Using Smart Structure Sensor Actuators for Stall Suppression

Abstract

Based on our previous experimental work conducted pertinent to the flow separation bubble burst control using a thin plate (hereafter burst control plate) attached to the leading-edge of laminar airfoils, the burst control plate in the current study is incorporated in the smart structure sensor actuators system on a NACA 631-012 airfoil for stall suppression, lift enhancement and drag reduction. The smart structure sensor actuators system uses a pressure transducer, a displacement sensor and a feedback controller to operate and to monitor the actuators in an autonomous mode. Note that the height of the burst control plate depends on the angular movement of the actuators located on either end of the airfoil section. Experimental studies were conducted at two different Reynolds numbers of 1.3 x 10 5 and 1.9 x 10 5 based on the airfoil chord length. The wind tunnel experiments demonstrated the effectiveness of the smart structure sensor actuators system and the burst control plate located at 6% chord-wise position (defined at the trailing-edge of the plate) of the airfoil, in that the drag is reduced, stall angle is delayed, and a significant improvement in the lift-to-drag ratio is achieved over a wide range of angles-of-attack. The feedback control approach provides a means to strengthen the vortical structures inside the separated shear layer with the overall drag of the airfoil is kept minimal. The experimental results demonstrated the application of the smart structure sensor actuators system and the burst control plate on the NACA 631-012 airfoil can be effective means of bubble burst control and airfoil stall suppression in low speed air vehicle applications.