Low-Order Nonlinear Models for Active Flow Control of a Low L/D Inlet Duct

This paper investigates the methodology to develop low-order nonlinear state space models for flow response along the centerline of a very aggressive (length to exit diameter ratio, L/D, of 1.5) inlet duct. Reduced order models are constructed by using Numerical Algorithms for State Space Subspace System Identification (N4SID), based on 2D numerical flow simulation data. The identified models successfully predict the spatially-averaged pressure recovery along the centerline at the Aerodynamic Interface Plane (AIP) for different levels of actuation of the control jets. Based on the identified models, estimator design and sensor placement are performed.