NARX Modeling and Extremum-Seeking Control of a Separation

A numerical study concerning a SISO active closed-loop separation control on a rounded step is presented. A first study of the synthetic jet frequency effect on the separation shows that the mean separation bubble surface is minimized if the mean pressure of a single wall pressure sensor is maximized. With the aim of designing a closed-loop strategy for the control of the recirculation bubble, a NARX black-box model of the pressure signal is identified using a single unsteady RANS simulation. The basic extremum- seeking algorithm is improved with an adaptive gain, to guarantee algorithm performance and this modification is validated against the nonlinear blackbox model of the forced flow. Then, the robust adaptive closed-loop is applied in realtime with an unsteady RANS simulation. Closed-loop results show the ability of the extremum-seeking control with adaptive gain to automatically control the separation, by minimizing the recirculation bubble surface using an unsteady RANS simulation.