Abstract
Aiming at the enhancement of mean lift and the suppression of lift fluctuation, effects of forcing on the flow around an NACA0012 airfoil is investigated by means of direct numerical simulation. The angle of attack is 10 degrees and the Reynolds number based on the freestream velocity and the chord length is 1000. A synthetic jet actuator is assumed to be installed on the lower surface of trailing edge. The actuator periodically gives the body force in the direction opposite to the uniform flow at a given frequency. First, we perform the open-loop control under different frequencies: it is found that at certain frequencies the mean lift force increases, but the fluctuation also increases. In order to suppress the lift fluctuation, we subsequently apply the closed-loop control, in which the frequency is dynamically optimized by using the extremum seeking. By the present closed-loop control, the lift fluctuation is found to be successfully suppressed, while the mean lift is kept high.
