Feedback Control and Estimation Applied to Boundary Layers Subject to Free-Stream Turbulence

This report results from a contract tasking KTH The Royal Institute of Technology as follows: The grantee will investigate and develop linear feedback control and estimation techniques for nonlinear wall-bounded transitional and turbulent flow phenomena, and to apply them in numerical closed-loop flow simulations. Control will be applied through blowing and suction at the wall to manage transition in boundary layers exposed to high levels of free-stream turbulence. Specifically, an estimation technique and full-state feedback control will be combined to compensate based upon wall information. To achieve this, full information feedback control will first be implemented in the numerical simulation of a spatially evolving boundary layer exposed to free-stream turbulence. Controller parameters will then be tuned in order to maximize performance. An estimation technique will then be implemented using an extended Kalman filter, and this will be tuned for performance as well. Finally, the controller and estimator will be combined, and the performance of the resulting output feedback compensator will be compared to that of the full information control. This approach represents a step forward in the applicability and realization of linear feedback control for realistic nonlinear control situations. The original document contains color images.