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Feedback control of instabilities in the two-dimensional Blasius boundary layer: The role of sensors and actuators

Author(s): Belson, Brandt A; Semeraro, Onofrio; Rowley, Clarence W; Henningson, Dan S

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Abstract: We analyze the effects of different types and positions of actuators and sensors on controllers’ performance and robustness in the linearized 2D Blasius boundary layer. The investigation is carried out using direct numerical simulations (DNS). To facilitate controller design, we find reduced-order models from the DNS data using a system identification procedure called the Eigensystem Realization Algorithm. Due to the highly convective nature of the boundary layer and corresponding time delays, the relative position of the actuator and sensor has a strong influence on the closed-loop dynamics. We address this issue by considering two different configurations. When the sensor is upstream of the actuator, corresponding to disturbance-feedforward control, good performance is observed, as in previous work. However, feedforward control can be degraded by additional disturbances or uncertainties in the plant model, and we demonstrate this. We then examine feedback controllers in which the sensor is a short distance downstream of the actuator. Sensors farther downstream of the actuator cause inherent time delays that limit achievable performance. The performance of the resulting feedback controllers depends strongly on the form of actuation introduced, the quantities sensed, and the observability of the structures deformed by the controller's action. These aspects are addressed by varying the spatial distribution of actuator and sensor. We find an actuator-sensor pair that is well-suited for feedback control, and demonstrate that it has good performance and robustness, even in the presence of unmodeled disturbances.
Publication Date: 2013
Citation: Belson, Brandt A, Semeraro, Onofrio, Rowley, Clarence W, Henningson, Dan S. "Feedback control of instabilities in the two-dimensional Blasius boundary layer: The role of sensors and actuators" Physics of Fluids, 25, 5, 054106 - 054106, doi:10.1063/1.4804390
DOI: doi:10.1063/1.4804390
ISSN: 1070-6631
Pages: 054106 - 054106
Type of Material: Journal Article
Journal/Proceeding Title: Physics of Fluids
Version: This is the publisher’s version of the article (version of record). All rights reserved to the publisher. Please refer to the publisher's site for terms of use.

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