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FEEDBACK CONTROL FOR LAMINARIZATION OF FLOW OVER WINGS

Reza Dadfar
Linne Flow Centre, KTH Mechanics SE-100 44 Stockholm, Sweden

Ardeshir Hanifi
Linne FLOW Centre and Swedish e-Science Research Centre (SeRC) KTH Mechanics, Royal Institute of Technology SE-100 44 Stockholm, Sweden; Swedish Defence Research Agency, FOI, SE-164 90 Stockholm, Sweden

Dan S. Henningson
Linne FLOW Centre and Swedish e-Science Research Centre (SeRC) KTH Mechanics, Royal Institute of Technology SE-100 44 Stockholm, Sweden

Abstract

An output feedback controller is designed to attenuate the amplitude of the Tollmien-Schlichting (TS) waves inside the boundary layer of an airfoil. The dynamics of the system are modelled by the linearised Naiver-Stokes equation. The impulse response to a generic initial condition is investigated. The perturbation evolves and penetrates inside the boundary layer and triggers the TS waves. A linear Gaussian controller based on the reduced order model is designed where the sensors and actuates are localised near the wall. An output projection is used to identify the unstable disturbances and the modes with large energy content in the TS wave frequency band; the objective function of the controller is selected as a set of Proper Orthogonal Decomposition (POD) modes. A plasma actuator is modelled and implemented as an external forcing on the flow. To account for the limitation of the plasma actuators several strategies are examined. The results are compared with an ideal LQG controller where the constraints are not accounted for the control design. The outcomes reveal successful performance in mitigating the amplitude of the wavepacket developing inside the boundary layer.