Frequency-domain based feedback control of flow separation using synthetic jets

Abstract

This research aims to facilitate feedback control of flow separation using synthetic jets. The effects of synthetic jets on flow separation are assessed via CFD simulations on a rounded backward-facing step. The NARMAX (Nonlinear Auto Regressive Moving Average with eXogenous inputs) system identification method is applied to develop a nonlinear flow model. Low-pass filtering is introduced as an effective method to facilitate a quasi-linear approximation of the nonlinear fluidic system including synthetic jet actuation in the frequency domain. Employing the describing function method, the approximate frequency response of the system is analyzed and implemented for the synthesis of a linear feedback controller. Finally, a PI controller is demonstrated to achieve tracking of a desired pressure with an improvement in the transient response over the open loop system.