{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/92747"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/92747","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Open-loop and closed-loop trailing-edge separation control on a natural laminar flow airfoil","abstract":"Active Unsteady Flow Control experiments were performed on a Natural Laminar Flow, NLF 0414 airfoil at Re = 1.0 × 10(6) in a 3-ft × 4-ft low-speed, low-turbulence wind tunnel. The NLF 0414 was designed with a region of favorable pressure gradient extending almost 70% of the chord on the upper surface of the airfoil. Aggressive pressure recovery in the aft 30% of the chord near the trailing edge results in the separation of the flow from the airfoil surface at the off-design conditions. The goal of this study was to control boundary-layer separation across the trailing-edge region of the airfoil in an effort to improve the performance beyond the designed angle-of-attack range. Active control of separation was achieved using a series of fast-switching solenoid valves connected to blowing slots at x/c = 0.75 on the upper surface of the airfoil. The airfoil in its baseline configuration was first evaluated to identify the dominant modes in the spectral content of unsteady Cp. Airfoil performance data were then acquired across a parametric range of blowing amplitudes, actuation frequencies and duty cycles in order to understand the effects of variations in the major forcing parameters on the performance of the model. Phase-averaged and phase locked planar PIV measurements were also acquired across a horizontal plane near the trailing-edge region of the airfoil model in order to examine the spatio-temporal evolution of the flowfield and understand the mechanism responsible for the alleviation of separation as a result of actuation at the different flow control settings. A closed loop controller was developed to vary the actuation parameters in-situ using sensory feedback from the unsteady surface pressure measurements. Adaptive modal decomposition methods were used to identify the frequencies of natural instabilities in the flowfield in real-time. A proportional controller was designed to automatically control the blowing amplitude by estimating the state of the flow and the extent of boundary-layer separation. The closed-loop system was able to simultaneously control the blowing amplitude and the actuation frequency such that a desired value of Cl was obtained.","abstract_html":"Active Unsteady Flow Control experiments were performed on a Natural Laminar Flow, NLF 0414 airfoil at Re = 1.0 × 10(6) in a 3-ft × 4-ft low-speed, low-turbulence wind tunnel. The NLF 0414 was designed with a region of favorable pressure gradient extending almost 70% of the chord on the upper surface of the airfoil. Aggressive pressure recovery in the aft 30% of the chord near the trailing edge results in the separation of the flow from the airfoil surface at the off-design conditions. The goal of this study was to control boundary-layer separation across the trailing-edge region of the airfoil in an effort to improve the performance beyond the designed angle-of-attack range. Active control of separation was achieved using a series of fast-switching solenoid valves connected to blowing slots at x/c = 0.75 on the upper surface of the airfoil. The airfoil in its baseline configuration was first evaluated to identify the dominant modes in the spectral content of unsteady Cp. Airfoil performance data were then acquired across a parametric range of blowing amplitudes, actuation frequencies and duty cycles in order to understand the effects of variations in the major forcing parameters on the performance of the model. Phase-averaged and phase locked planar PIV measurements were also acquired across a horizontal plane near the trailing-edge region of the airfoil model in order to examine the spatio-temporal evolution of the flowfield and understand the mechanism responsible for the alleviation of separation as a result of actuation at the different flow control settings. A closed loop controller was developed to vary the actuation parameters in-situ using sensory feedback from the unsteady surface pressure measurements. Adaptive modal decomposition methods were used to identify the frequencies of natural instabilities in the flowfield in real-time. A proportional controller was designed to automatically control the blowing amplitude by estimating the state of the flow and the extent of boundary-layer separation. The closed-loop system was able to simultaneously control the blowing amplitude and the actuation frequency such that a desired value of Cl was obtained.","abstract_has_math":false,"creators":["Gupta, Rohit"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Aerospace Engineering","degree_department":null,"school":null,"contributors":["Ansell, Phillip J."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2016,"date_issued":"2016-11-10T17:50:04Z","date_published":"2016-11-10T17:50:04Z","updated_at":"2026-07-22T22:26:35Z","subjects":["Unsteady Aerodynamics","Active Flow Control","Natural Laminar Flow","Particle Image Velocimetry"],"languages":["en"],"rights":["Copyright 2016 by Rohit Gupta"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/92747","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Ansell, Phillip J."]},{"key":"dc:creator","label":"Author","values":["Gupta, Rohit"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2016-11-10T17:50:04Z","2016-07-07","2016-08"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Aerospace Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Unsteady Aerodynamics","Active Flow Control","Natural Laminar Flow","Particle Image Velocimetry"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2016 by Rohit Gupta"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/92747"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Active Unsteady Flow Control experiments were performed on a Natural Laminar Flow, NLF 0414 airfoil at Re = 1.0 × 10(6) in a 3-ft × 4-ft low-speed, low-turbulence wind tunnel. The NLF 0414 was designed with a region of favorable pressure gradient extending almost 70% of the chord on the upper surface of the airfoil. Aggressive pressure recovery in the aft 30% of the chord near the trailing edge results in the separation of the flow from the airfoil surface at the off-design conditions. The goal of this study was to control boundary-layer separation across the trailing-edge region of the airfoil in an effort to improve the performance beyond the designed angle-of-attack range. Active control of separation was achieved using a series of fast-switching solenoid valves connected to blowing slots at x/c = 0.75 on the upper surface of the airfoil. The airfoil in its baseline configuration was first evaluated to identify the dominant modes in the spectral content of unsteady Cp. Airfoil performance data were then acquired across a parametric range of blowing amplitudes, actuation frequencies and duty cycles in order to understand the effects of variations in the major forcing parameters on the performance of the model. Phase-averaged and phase locked planar PIV measurements were also acquired across a horizontal plane near the trailing-edge region of the airfoil model in order to examine the spatio-temporal evolution of the flowfield and understand the mechanism responsible for the alleviation of separation as a result of actuation at the different flow control settings. A closed loop controller was developed to vary the actuation parameters in-situ using sensory feedback from the unsteady surface pressure measurements. Adaptive modal decomposition methods were used to identify the frequencies of natural instabilities in the flowfield in real-time. A proportional controller was designed to automatically control the blowing amplitude by estimating the state of the flow and the extent of boundary-layer separation. The closed-loop system was able to simultaneously control the blowing amplitude and the actuation frequency such that a desired value of Cl was obtained.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2016-11-09 without embargo terms","The student, Rohit Gupta, accepted the attached license on 2016-07-01 at 17:51.","The student, Rohit Gupta, submitted this Thesis for approval on 2016-07-01 at 18:04.","This Thesis was approved for publication on 2016-07-07 at 08:43.","DSpace SAF Submission Ingestion Package generated from Vireo submission #9746 on 2016-11-09 at 10:22:36","Made available in DSpace on 2016-11-10T17:50:04Z (GMT). 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Aggressive pressure recovery in the aft 30% of the chord near the trailing edge results in the separation of the flow from the airfoil surface at the off-design conditions. The goal of this study was to control boundary-layer separation across the trailing-edge region of the airfoil in an effort to improve the performance beyond the designed angle-of-attack range. Active control of separation was achieved using a series of fast-switching solenoid valves connected to blowing slots at x/c = 0.75 on the upper surface of the airfoil. The airfoil in its baseline configuration was first evaluated to identify the dominant modes in the spectral content of unsteady Cp. Airfoil performance data were then acquired across a parametric range of blowing amplitudes, actuation frequencies and duty cycles in order to understand the effects of variations in the major forcing parameters on the performance of the model. Phase-averaged and phase locked planar PIV measurements were also acquired across a horizontal plane near the trailing-edge region of the airfoil model in order to examine the spatio-temporal evolution of the flowfield and understand the mechanism responsible for the alleviation of separation as a result of actuation at the different flow control settings. A closed loop controller was developed to vary the actuation parameters in-situ using sensory feedback from the unsteady surface pressure measurements. Adaptive modal decomposition methods were used to identify the frequencies of natural instabilities in the flowfield in real-time. A proportional controller was designed to automatically control the blowing amplitude by estimating the state of the flow and the extent of boundary-layer separation. The closed-loop system was able to simultaneously control the blowing amplitude and the actuation frequency such that a desired value of Cl was obtained.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2016-11-09 without embargo terms","The student, Rohit Gupta, accepted the attached license on 2016-07-01 at 17:51.","The student, Rohit Gupta, submitted this Thesis for approval on 2016-07-01 at 18:04.","This Thesis was approved for publication on 2016-07-07 at 08:43.","DSpace SAF Submission Ingestion Package generated from Vireo submission #9746 on 2016-11-09 at 10:22:36","Made available in DSpace on 2016-11-10T17:50:04Z (GMT). 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