Adaptive flow separation control over an asymmetric airfoil

Abstract

A closed-loop adaptive flow control system was experimentally demonstrated to control the flow separation over an NACA 64A210 airfoil. To control the flow separation, piezoelectrically driven synthetic jet actuators and pressure sensors were used. Before performing the closed-loop flow separation control experiment, the effectiveness of the synthetic jet actuator was investigated by open-loop experiments for an NACA 64A210 airfoil in various operating conditions to examine the effective control parameter. The pressure gradient, which was calculated from the difference of mean pressure coefficients between two sensor positions, was found to be a criterion for flow recovery in these experiments. Therefore, the pressure gradient was selected as a control parameter for separated flow. An adaptive flow control system using adaptive inverse control and extremum-seeking control was developed to control the pressure gradient for separated flow over an NACA 64A210 airfoil. The performance of the resulting flow control system was compared with a simple MD control system. Experimental results based on the proposed adaptive flow control system demonstrated the satisfactory tracking performance of the pressure gradient for the pressure recovery. As a result, the proposed adaptive flow control approach enhanced the aerodynamics performances in terms of lift and drag coefficients and lift/drag ratio in the closed-loop control system.