{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/23019"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/23019","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"The evolution of vortices in a turbulent boundary layer","abstract":"Most scientists would agree that the greatest unsolved problem of fluid mechanics is turbulence. Turbulence is not only an intellectual challenge to mathematicians and theorists, it is also of practical interest since the highly dissipative and dispersive nature of turbulence has a significant impact on many applications. Over the years, many investigations have yielded descriptions of turbulent velocity fields and hypotheses for the physical basis of turbulence; however, the fundamental physics of turbulence remain unknown. In this investigation, the evolution of a perturbed vortex tube near a boundary is examined in order to gain insight into turbulent boundary layer phenomena. A Lagrangian vortex model is used to describe the vortex tube evolution, including the influence of shear. Based on numerical calculations, it is shown that small perturbations evolve into large horseshoe-shaped vortex structures which have been observed in laboratory experiments and direct numerical solutions of the Navier-Stokes equations. Additionally, horseshoe-shaped vortices are shown to collapse and form vortex rings which have also been reported in experimental investigations. The motion of evolving vortices is shown to provide a physical basis for enhanced momentum transport and observed inclinations of vorticity. In addition, collections of vortices are shown to provide an inviscid basis for mean velocity gradients and random-appearing, yet well correlated, velocity fluctuations.","abstract_html":"Most scientists would agree that the greatest unsolved problem of fluid mechanics is turbulence. Turbulence is not only an intellectual challenge to mathematicians and theorists, it is also of practical interest since the highly dissipative and dispersive nature of turbulence has a significant impact on many applications. Over the years, many investigations have yielded descriptions of turbulent velocity fields and hypotheses for the physical basis of turbulence; however, the fundamental physics of turbulence remain unknown. In this investigation, the evolution of a perturbed vortex tube near a boundary is examined in order to gain insight into turbulent boundary layer phenomena. A Lagrangian vortex model is used to describe the vortex tube evolution, including the influence of shear. Based on numerical calculations, it is shown that small perturbations evolve into large horseshoe-shaped vortex structures which have been observed in laboratory experiments and direct numerical solutions of the Navier-Stokes equations. Additionally, horseshoe-shaped vortices are shown to collapse and form vortex rings which have also been reported in experimental investigations. The motion of evolving vortices is shown to provide a physical basis for enhanced momentum transport and observed inclinations of vorticity. In addition, collections of vortices are shown to provide an inviscid basis for mean velocity gradients and random-appearing, yet well correlated, velocity fluctuations.","abstract_has_math":false,"creators":["Kempka, Steven Norman"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Mechanical Science and Engineering","degree_department":null,"school":null,"contributors":["Dunn, William E."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T13:59:16Z","date_published":"2011-05-07T13:59:16Z","updated_at":"2026-07-22T22:25:21Z","subjects":["Engineering, Mechanical"],"languages":["eng"],"rights":["Copyright 1989 Kempka, Steven Norman"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI8924858","(UMI)AAI8924858"],"render_values":[{"text":"AAI8924858","href":null,"code":true},{"text":"(UMI)AAI8924858","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/23019","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Dunn, William E."]},{"key":"dc:creator","label":"Author","values":["Kempka, Steven Norman"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T13:59:16Z","10000-01-01","1989"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Science and Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"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":["Engineering, Mechanical"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1989 Kempka, Steven Norman"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI8924858","(UMI)AAI8924858","http://hdl.handle.net/2142/23019"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Most scientists would agree that the greatest unsolved problem of fluid mechanics is turbulence. Turbulence is not only an intellectual challenge to mathematicians and theorists, it is also of practical interest since the highly dissipative and dispersive nature of turbulence has a significant impact on many applications. Over the years, many investigations have yielded descriptions of turbulent velocity fields and hypotheses for the physical basis of turbulence; however, the fundamental physics of turbulence remain unknown. In this investigation, the evolution of a perturbed vortex tube near a boundary is examined in order to gain insight into turbulent boundary layer phenomena. A Lagrangian vortex model is used to describe the vortex tube evolution, including the influence of shear. Based on numerical calculations, it is shown that small perturbations evolve into large horseshoe-shaped vortex structures which have been observed in laboratory experiments and direct numerical solutions of the Navier-Stokes equations. Additionally, horseshoe-shaped vortices are shown to collapse and form vortex rings which have also been reported in experimental investigations. The motion of evolving vortices is shown to provide a physical basis for enhanced momentum transport and observed inclinations of vorticity. In addition, collections of vortices are shown to provide an inviscid basis for mean velocity gradients and random-appearing, yet well correlated, velocity fluctuations.","Made available in DSpace on 2011-05-07T13:59:16Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 8924858.pdf: 8973719 bytes, checksum: 365121b1a0c8d4dd029db9f9050aa7fe (MD5) Previous issue date: 1989","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T15:01:37Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:29:14-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"]},{"key":"dc:title","label":"Title","values":["The evolution of vortices in a turbulent boundary layer"]}]}],"canonical_facts":{"dc:contributor":["Dunn, William E."],"dc:creator":["Kempka, Steven Norman"],"dc:date":["2011-05-07T13:59:16Z","10000-01-01","1989"],"dc:description":["Most scientists would agree that the greatest unsolved problem of fluid mechanics is turbulence. Turbulence is not only an intellectual challenge to mathematicians and theorists, it is also of practical interest since the highly dissipative and dispersive nature of turbulence has a significant impact on many applications. Over the years, many investigations have yielded descriptions of turbulent velocity fields and hypotheses for the physical basis of turbulence; however, the fundamental physics of turbulence remain unknown. In this investigation, the evolution of a perturbed vortex tube near a boundary is examined in order to gain insight into turbulent boundary layer phenomena. A Lagrangian vortex model is used to describe the vortex tube evolution, including the influence of shear. Based on numerical calculations, it is shown that small perturbations evolve into large horseshoe-shaped vortex structures which have been observed in laboratory experiments and direct numerical solutions of the Navier-Stokes equations. Additionally, horseshoe-shaped vortices are shown to collapse and form vortex rings which have also been reported in experimental investigations. The motion of evolving vortices is shown to provide a physical basis for enhanced momentum transport and observed inclinations of vorticity. In addition, collections of vortices are shown to provide an inviscid basis for mean velocity gradients and random-appearing, yet well correlated, velocity fluctuations.","Made available in DSpace on 2011-05-07T13:59:16Z (GMT). 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