Advance in Boundary Layer Control: Robust Reduced-Order Transition Controller

A framework to derive optimal and robust reduced-order controllers of transitional boundary layers using linear-quadratic-Gaussian (LQG) design, or, in modern terms, H2 design, is presented. As a test case, two-dimensional Poiseuille flow is considered. A controller based on a reduced model, 8% of the order of the full size system, is designed. Initial conditions creating transient growth of wall-shear stresses are constructed. The controller is tested on a 32 wave numbers simulation. Wall-shear stresses reduction, up to 90%, is obtained. The transferability of the controller to Navier-Stokes simulations and engineering applications is discussed. Corresponding author: Telephone (310) 206-2732, Facsimile (310) 206-6673, E-mail: crtlz@math.ucla.edu The reduction of drag produced by skin friction, or, in other words, the reduction of wall-shear stresses (WSS) generated by near-wall turbulence have received wide attention. "The skin friction constitutes about 50%, 90%, and 100% of the ..