The need for prediction in feedback control of a mixing layer

Tamir Shaqarin (1) , Bernd R. Noack , Marek Morzyński (2)

1 Tafila Technical University
2 PUT - Poznan University of Technology

We present the first application of a Smith predictor in the model-based feedback control of a convectively unstable flow. The two-dimensional incompressible mixing layer is chosen as a plant and integrated with a finite-element Navier–Stokes solver. The flow is actuated by a modulation of the inflow mimicking a pulsed jet actuator. The state is monitored by a down-stream velocity sensor. The control goal is to command the fluctuation level at the sensor location. As an additional challenge, the incoming shear-flow profile is perturbed by the small noise level. The starting point of this study is a standard low-order control without prediction. A Smith predictor is included to compensate for the convective delay from actuation to sensing. The closed-loop results with a Smith predictor are distinctly better than without it. The design of the linear robust controllers is performed with an open-loop control. We conjecture that predictors may augment feedback control for a large class of convectively unstable flows with significant time-delay from actuation to sensing.

Domaines: Mécanique des fluides [physics.class-ph]

Tamir Shaqarin, Bernd R. Noack, Marek Morzyński. The need for prediction in feedback control of a mixing layer. Fluid Dynamics Research, 2018, 50 (6), pp.065514. ⟨10.1088/1873-7005/aae453⟩. ⟨hal-02398659⟩