Aircraft, turbomachinery, wind turbines, and other systems that generate or rely on aerodynamic forces are designed to operate most efficiently when flows are fully attached. However, especially due to increasing off-design performance requirements, there is significant risk of inefficient operation or failure due to flow separation. This work formulates a procedure for extending the performance envelope of many fluidic systems by delaying flow separation through real time separated flow state estimation and control. The history of active separation control is rich; however the approach presented here is novel in that it employs "real time" dynamical system updates to track nonlinear variations in the flow and provide robustness to flow state conditions. First, the dynamics of the canonical laminar separated flow over a flat plate at Rec=10⁵ are characterized by employing full-field, time-resolved PIV and unsteady surface pressure measurements. Dynamic Mode Decomposition (DMD) is employed on the high dimensional PIV velocity fields to identify the dynamically relevant spatial structure and temporal characteristics of the separated flow. Then, results of various cases of open-loop control using a zero-net mass flux actuator slot located just upstream of separation are presented that show separation reduction occurs for the employed actuation method. Real time estimates of the dynamical characteristics are provided by performing online DMD on measurements from a linear array of unsteady surface pressure transducers. The results show that online DMD of the pressure measurements provides reliable estimates of the modal characteristics of the separated flow subject to forcing. Furthermore, the dynamical estimates are updated at a rate commensurate with the characteristic time scales of the flow. Therefore, as the separated flow reacts to the applied forcing, online DMD applied to the surface pressure measurements provides a time-varying linear estimate of the evolution of the flow. Building upon these results, methods for adaptive control of flow separation based on the model provided by online DMD are formulated and implemented on the separated flow. Feedback control is implemented in which Linear Quadratic Regulator gains are computed recursively as the model provided by online DMD is updated. This physics-motivated, autonomous approach results in more efficient flow reattachment, requiring approximately 30% less actuator effort as compared with the commensurate open loop forcing case. Since this approach relies solely on observations of the separated flow, it is robust to variable flow conditions. Additionally, this approach does not require prior knowledge of the characteristics of the separated flow. / A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2018. / June 12, 2018. / Adaptive Control, Dynamic Mode Decomposition, Flow Control, Laminar Separation / Includes bibliographical references. / Louis N. Cattafesta, Professor Directing Dissertation; Mark Sussman, University Representative; Kunihiko Taira, Committee Member; Emmanuel Collins, Committee Member; Matthew Moore, Committee Member; Maziar Hemati, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_647215 |
| Contributors | Deem, Eric Anthony (author), Cattafesta, Louis N. (professor directing dissertation), Sussman, Mark (university representative), Taira, Kunihiko (committee member), Collins, E. (committee member), Moore, Matthew Nicholas J. (committee member), Hemati, Maziar (committee member), Florida State University (degree granting institution), College of Engineering (degree granting college), Department of Mechanical Engineering (degree granting departmentdgg) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text, doctoral thesis |
| Format | 1 online resource (148 pages), computer, application/pdf |
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