Development of model-based sensors and their use for closed-loop control of separated shear flows

Closed-loop control of separated flows is still hindered by a lack of fast and practical sensors for the measurement of the length of a separation bubble or of the position of reattachment. Therefore, a new real-time algorithm for the online detection of flow states is developed to overcome this limitation. For a model-based sensor microphone measurements in the separation zone are exploited and a control concept is outlined. The actuated backward-facing step flow is chosen as a benchmark configuration in which the length of the separated flow region is to be controlled. A closed-loop setup with a robust controller is implemented and studied experimentally showing a much better performance compared to a former approach. Based on the analysis of microphone signals a second model-based sensor for tracking of coherent vortical structures is proposed, too, and an extended control concept is outlined.