Robust Multivariable Closed-Loop Control of a Turbulent Backward-Facing Step Flow

Active control of separated flows has become an attractive approach enabling the designer to meet increased performance demands for various systems. Whereas a significant part of the work published so far in the area of closed-loop flow control is based on simulation studies, this paper presents an example of a successful application of a multivariable controller in wind tunnel experiments. A robust H ∞ controller is used to control the spanwise variable reattachment length downstream of a benchmark problem, the backward-facing step. To reduce the conservatism of this approach, a nonlinear static precompensation is included, first. The synthesis of the controller is based on a family of identified linear black-box models, which describe the compensated input/output behavior of the plant. Tracking performance and disturbance rejection of the controller are tested in wind tunnel experiments and shown in this paper.