Robust control of uncertain cylinder wake flows based on robust reduced order models

A technique for the construction of robust orthogonal flow bases, to be used for model reduction and flow control, is proposed. The construction accounts for the dependence of the flow structures with the control and variability in the flow conditions. Numerical examples, for the two-dimensional flow around a circular cylinder in laminar regime, are provided to demonstrate the robust character of the resulting reduced basis. The control of the flow is then considered with the objective of reducing the body drag in a full information framework, by blowing/suction at the cylinder surface. Different control strategies are considered, some being also robust in the sense that they incorporate variability in the flow conditions (Reynolds number). The improvements brought by the robust basis and robust control strategies is evidenced for the control of the reduced model and, more important, when the control laws determined for the reduced model are applied to the fully detailed flow model (DNS).