Drag reduction by closed-loop control of a separated flow over a bluff body with a blunt trailing edge

The present investigation focuses on the drag reduction of a bluff body with a blunt trailing edge in wind tunnel experiments. Two different approaches of closed-loop control are presented. First, a robust controller based on a family of linear black-box models is designed to suppress the vortex shedding by controlling the base pressure. To reduce the conservatism of this approach, a nonlinear static precompensation is included. In the second approach, a model-based based sensor and an extremum seeking controller are combined to determine the optimal phase of the actuation to synchronise the vortex shedding. It is shown that the synchronisation of the vortex shedding leads to a more efficient drag reduction with respect to energy.