Robust Stabilization of Laminar Flows in Varying Flow Regimes

The stabilization of laminar flows on the base of linearizations and feedback controllers has been the subject of many recent theoretical and computational studies. However, the applicability of the standard approaches is limited due to the inherent fragility of observer based controllers with respect to arbitrary small changes in the system. We show that a slight variation in the Reynolds number of a flow setup amounts to a coprime factor perturbation in the associated linear transfer function. Based on these findings, we argue that known concepts from robust control can be exploited to come up with an output feedback law that can stabilize the cylinder wake over the transition period from a stable to a stabilized regime.