{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/101818"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/101818","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"The influence of steps topography on the behavior of density currents – a numerical study","abstract":"Recent advances in high-resolution multibeam bathymetric imaging have revealed step-like structures interpreted as cyclic steps, or sediment waves, along the bottom of deep-sea canyons and channel levees. These bed features are formed by turbidity currents, and in turn, influence the flow characteristics of the density currents and their sediment transport behavior, thus affecting sedimentation in the oceans. To explore the interaction between density currents and stepped topographies, a series of depth-resolved numerical experiments with a lock-exchange setup were conducted using k-epsilon, two-dimensional and three-dimensional Large Eddy Simulation (LES) models. The results of the present study clearly indicate that compared with a constant slope bed, vertical steps, or “stair-case” shaped bed topographies significantly decrease the overall dense fluid transport efficiency, cause a much more rapid loss of dense fluid at the density current head, and preferentially trap dense fluid at the leeside of steps, thereby decelerating the current front at the late stage of flow evolution. Density underflow over a series of steps with smooth downward-concave geometries behaves largely similarly to the flow over a constant slope bed. To a much lesser degree, an increase in step size causes an effect similar to imposing a vertical step bed. While simulations with the three-dimensional LES numerical model most accurately represent the flow behavior, the k-e model represents vortex generation poorly and the two-dimensional LES model represents only weak eddy dissipation.","abstract_html":"Recent advances in high-resolution multibeam bathymetric imaging have revealed step-like structures interpreted as cyclic steps, or sediment waves, along the bottom of deep-sea canyons and channel levees. These bed features are formed by turbidity currents, and in turn, influence the flow characteristics of the density currents and their sediment transport behavior, thus affecting sedimentation in the oceans. To explore the interaction between density currents and stepped topographies, a series of depth-resolved numerical experiments with a lock-exchange setup were conducted using k-epsilon, two-dimensional and three-dimensional Large Eddy Simulation (LES) models. The results of the present study clearly indicate that compared with a constant slope bed, vertical steps, or “stair-case” shaped bed topographies significantly decrease the overall dense fluid transport efficiency, cause a much more rapid loss of dense fluid at the density current head, and preferentially trap dense fluid at the leeside of steps, thereby decelerating the current front at the late stage of flow evolution. Density underflow over a series of steps with smooth downward-concave geometries behaves largely similarly to the flow over a constant slope bed. To a much lesser degree, an increase in step size causes an effect similar to imposing a vertical step bed. While simulations with the three-dimensional LES numerical model most accurately represent the flow behavior, the k-e model represents vortex generation poorly and the two-dimensional LES model represents only weak eddy dissipation.","abstract_has_math":false,"creators":["Zhao, Zihe"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Geology","degree_department":null,"school":null,"contributors":["Best, James Leonard","Parker, Gary","Jewett, Brian Ford"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-09-27T16:47:34Z","date_published":"2018-09-27T16:47:34Z","updated_at":"2026-07-22T22:24:40Z","subjects":["turbidity currents","cyclic steps","numerical model"],"languages":["en"],"rights":["Copyright 2018 Zihe Zhao"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/101818","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Best, James Leonard","Parker, Gary","Jewett, Brian Ford"]},{"key":"dc:creator","label":"Author","values":["Zhao, Zihe"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2018-09-27T16:47:34Z","2020-09-28T09:15:19Z","2018-07-12","2018-08"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Geology"]},{"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":["turbidity currents","cyclic steps","numerical model"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2018 Zihe Zhao"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/101818"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Recent advances in high-resolution multibeam bathymetric imaging have revealed step-like structures interpreted as cyclic steps, or sediment waves, along the bottom of deep-sea canyons and channel levees. These bed features are formed by turbidity currents, and in turn, influence the flow characteristics of the density currents and their sediment transport behavior, thus affecting sedimentation in the oceans. To explore the interaction between density currents and stepped topographies, a series of depth-resolved numerical experiments with a lock-exchange setup were conducted using k-epsilon, two-dimensional and three-dimensional Large Eddy Simulation (LES) models. The results of the present study clearly indicate that compared with a constant slope bed, vertical steps, or “stair-case” shaped bed topographies significantly decrease the overall dense fluid transport efficiency, cause a much more rapid loss of dense fluid at the density current head, and preferentially trap dense fluid at the leeside of steps, thereby decelerating the current front at the late stage of flow evolution. Density underflow over a series of steps with smooth downward-concave geometries behaves largely similarly to the flow over a constant slope bed. To a much lesser degree, an increase in step size causes an effect similar to imposing a vertical step bed. While simulations with the three-dimensional LES numerical model most accurately represent the flow behavior, the k-e model represents vortex generation poorly and the two-dimensional LES model represents only weak eddy dissipation.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2020-08-01","The student, Zihe Zhao, accepted the attached license on 2018-07-11 at 19:01.","The student, Zihe Zhao, submitted this Thesis for approval on 2018-07-11 at 19:21.","This Thesis was approved for publication on 2018-07-12 at 15:01.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12840 on 2018-09-27 at 11:37:07","Made available in DSpace on 2018-09-27T16:47:34Z (GMT). No. of bitstreams: 6 ZHAO-THESIS-2018.pdf: 6800420 bytes, checksum: 63c3ed98d7d67bc8252c55de43cfb12e (MD5) Animation 3dLES.mp4: 15846090 bytes, checksum: 79e476ee5e34807d38dd76ea41bedf76 (MD5) Animation mediumssteps.mp4: 10127366 bytes, checksum: 1733f8de78587d42a5dc13d48549b1d1 (MD5) Animation mediumvsteps.mp4: 11306353 bytes, checksum: dd0d99a96c1ab02aa1b92b2ff71319fc (MD5) Animation slope.mp4: 7871065 bytes, checksum: b25feab98c299028d9d183ffd36563c2 (MD5) LICENSE.txt: 4206 bytes, checksum: 492dfab3caa9e5ece367209780e93f78 (MD5) Previous issue date: 2018-07-12","Embargo set by: Seth Robbins for item 107919 Lift date: 2020-09-27T16:47:41Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 107919 on 2020-09-28T09:15:19Z."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["The influence of steps topography on the behavior of density currents – a numerical study"]}]}],"canonical_facts":{"dc:contributor":["Best, James Leonard","Parker, Gary","Jewett, Brian Ford"],"dc:creator":["Zhao, Zihe"],"dc:date":["2018-09-27T16:47:34Z","2020-09-28T09:15:19Z","2018-07-12","2018-08"],"dc:description":["Recent advances in high-resolution multibeam bathymetric imaging have revealed step-like structures interpreted as cyclic steps, or sediment waves, along the bottom of deep-sea canyons and channel levees. These bed features are formed by turbidity currents, and in turn, influence the flow characteristics of the density currents and their sediment transport behavior, thus affecting sedimentation in the oceans. To explore the interaction between density currents and stepped topographies, a series of depth-resolved numerical experiments with a lock-exchange setup were conducted using k-epsilon, two-dimensional and three-dimensional Large Eddy Simulation (LES) models. The results of the present study clearly indicate that compared with a constant slope bed, vertical steps, or “stair-case” shaped bed topographies significantly decrease the overall dense fluid transport efficiency, cause a much more rapid loss of dense fluid at the density current head, and preferentially trap dense fluid at the leeside of steps, thereby decelerating the current front at the late stage of flow evolution. Density underflow over a series of steps with smooth downward-concave geometries behaves largely similarly to the flow over a constant slope bed. To a much lesser degree, an increase in step size causes an effect similar to imposing a vertical step bed. While simulations with the three-dimensional LES numerical model most accurately represent the flow behavior, the k-e model represents vortex generation poorly and the two-dimensional LES model represents only weak eddy dissipation.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2020-08-01","The student, Zihe Zhao, accepted the attached license on 2018-07-11 at 19:01.","The student, Zihe Zhao, submitted this Thesis for approval on 2018-07-11 at 19:21.","This Thesis was approved for publication on 2018-07-12 at 15:01.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12840 on 2018-09-27 at 11:37:07","Made available in DSpace on 2018-09-27T16:47:34Z (GMT). No. of bitstreams: 6 ZHAO-THESIS-2018.pdf: 6800420 bytes, checksum: 63c3ed98d7d67bc8252c55de43cfb12e (MD5) Animation 3dLES.mp4: 15846090 bytes, checksum: 79e476ee5e34807d38dd76ea41bedf76 (MD5) Animation mediumssteps.mp4: 10127366 bytes, checksum: 1733f8de78587d42a5dc13d48549b1d1 (MD5) Animation mediumvsteps.mp4: 11306353 bytes, checksum: dd0d99a96c1ab02aa1b92b2ff71319fc (MD5) Animation slope.mp4: 7871065 bytes, checksum: b25feab98c299028d9d183ffd36563c2 (MD5) LICENSE.txt: 4206 bytes, checksum: 492dfab3caa9e5ece367209780e93f78 (MD5) Previous issue date: 2018-07-12","Embargo set by: Seth Robbins for item 107919 Lift date: 2020-09-27T16:47:41Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 107919 on 2020-09-28T09:15:19Z."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/101818"],"dc:language":["en"],"dc:rights":["Copyright 2018 Zihe Zhao"],"dc:subject":["turbidity currents","cyclic steps","numerical model"],"dc:title":["The influence of steps topography on the behavior of density currents – a numerical study"],"dc:type":["text"],"thesis:degree_discipline":["Geology"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:40Z"}