{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/112371"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/112371","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Investigation of velocity gradient as driving force of flow pulsation in fuel assemblies","abstract":"The presence of quasi-periodic flow pulsations in fuel assemblies has been observed since the 1960's but is still not fully understood. Current design and licensing practices for nuclear reactor fuel mostly rely on 1-dimensional subchannel simulation tools, which might not accurately predict the increased subchannel mixing caused by flow pulsations. The present work develops a quantitative relationship between subchannel mixing and the inter-subchannel velocity gradient, shown to be the driving force of flow pulsation. A sensitivity study on rod-bundle geometry, based on an experiment by Bardet and Balaras at George Washington University, was conducted with a URANS method in transient simulations using the commercial software Star-CCM+. A linear relationship was observed between crossflow mixing and [delta]vbulk, defined as the difference in bulk velocities of adjacent subchannels. A threshold value of [delta]vbulk was seen close to 0.4 m/s, below which very little crossflow mixing was observed. Using these results, an analytical relationship between inter-subchannel velocity gradient and crossflow mixing could be developed and implemented into subchannel codes for more accurate modeling of flow in a fuel assembly.","abstract_html":"The presence of quasi-periodic flow pulsations in fuel assemblies has been observed since the 1960's but is still not fully understood. Current design and licensing practices for nuclear reactor fuel mostly rely on 1-dimensional subchannel simulation tools, which might not accurately predict the increased subchannel mixing caused by flow pulsations. The present work develops a quantitative relationship between subchannel mixing and the inter-subchannel velocity gradient, shown to be the driving force of flow pulsation. A sensitivity study on rod-bundle geometry, based on an experiment by Bardet and Balaras at George Washington University, was conducted with a URANS method in transient simulations using the commercial software Star-CCM+. A linear relationship was observed between crossflow mixing and [delta]vbulk, defined as the difference in bulk velocities of adjacent subchannels. A threshold value of [delta]vbulk was seen close to 0.4 m/s, below which very little crossflow mixing was observed. Using these results, an analytical relationship between inter-subchannel velocity gradient and crossflow mixing could be developed and implemented into subchannel codes for more accurate modeling of flow in a fuel assembly.","abstract_has_math":false,"creators":["Everett, Patrick F"],"institution":"Massachusetts Institute of Technology","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Nuclear Science and Engineering.","school":null,"contributors":[],"advisors":["Emilio Baglietto."],"committee_chairs":[],"committee_members":[],"year":2017,"date_issued":"2017","date_published":"2017","updated_at":"2026-07-22T22:22:24Z","subjects":["Nuclear Science and Engineering."],"languages":["eng"],"rights":["MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."],"rights_urls":["http://dspace.mit.edu/handle/1721.1/7582"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/1721.1/112371","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Emilio Baglietto."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. Department of Nuclear Science and Engineering."]},{"key":"dc:contributor.other","label":"Dc Contributor Other","values":["Massachusetts Institute of Technology. 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They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://dspace.mit.edu/handle/1721.1/7582"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/1721.1/112371"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Thesis: S.B., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.","This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.","Cataloged from student-submitted PDF version of thesis.","Includes bibliographical references (pages 24-26)."]},{"key":"dc:description.abstract","label":"Abstract","values":["The presence of quasi-periodic flow pulsations in fuel assemblies has been observed since the 1960's but is still not fully understood. Current design and licensing practices for nuclear reactor fuel mostly rely on 1-dimensional subchannel simulation tools, which might not accurately predict the increased subchannel mixing caused by flow pulsations. The present work develops a quantitative relationship between subchannel mixing and the inter-subchannel velocity gradient, shown to be the driving force of flow pulsation. A sensitivity study on rod-bundle geometry, based on an experiment by Bardet and Balaras at George Washington University, was conducted with a URANS method in transient simulations using the commercial software Star-CCM+. A linear relationship was observed between crossflow mixing and [delta]vbulk, defined as the difference in bulk velocities of adjacent subchannels. A threshold value of [delta]vbulk was seen close to 0.4 m/s, below which very little crossflow mixing was observed. Using these results, an analytical relationship between inter-subchannel velocity gradient and crossflow mixing could be developed and implemented into subchannel codes for more accurate modeling of flow in a fuel assembly."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["S.B."]},{"key":"dc:title","label":"Title","values":["Investigation of velocity gradient as driving force of flow pulsation in fuel assemblies"]}]}],"canonical_facts":{"dc:contributor.advisor":["Emilio Baglietto."],"dc:contributor.department":["Massachusetts Institute of Technology. Department of Nuclear Science and Engineering."],"dc:contributor.other":["Massachusetts Institute of Technology. Department of Nuclear Science and Engineering."],"dc:creator":["Everett, Patrick F"],"dc:date.accessioned":["2017-12-05T16:24:58Z"],"dc:date.available":["2017-12-05T16:24:58Z"],"dc:date.issued":["2017"],"dc:description":["Thesis: S.B., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.","This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.","Cataloged from student-submitted PDF version of thesis.","Includes bibliographical references (pages 24-26)."],"dc:description.abstract":["The presence of quasi-periodic flow pulsations in fuel assemblies has been observed since the 1960's but is still not fully understood. Current design and licensing practices for nuclear reactor fuel mostly rely on 1-dimensional subchannel simulation tools, which might not accurately predict the increased subchannel mixing caused by flow pulsations. The present work develops a quantitative relationship between subchannel mixing and the inter-subchannel velocity gradient, shown to be the driving force of flow pulsation. A sensitivity study on rod-bundle geometry, based on an experiment by Bardet and Balaras at George Washington University, was conducted with a URANS method in transient simulations using the commercial software Star-CCM+. A linear relationship was observed between crossflow mixing and [delta]vbulk, defined as the difference in bulk velocities of adjacent subchannels. A threshold value of [delta]vbulk was seen close to 0.4 m/s, below which very little crossflow mixing was observed. Using these results, an analytical relationship between inter-subchannel velocity gradient and crossflow mixing could be developed and implemented into subchannel codes for more accurate modeling of flow in a fuel assembly."],"dc:description.degree":["S.B."],"dc:identifier.uri":["http://hdl.handle.net/1721.1/112371"],"dc:language.iso":["eng"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."],"dc:rights.uri":["http://dspace.mit.edu/handle/1721.1/7582"],"dc:subject":["Nuclear Science and Engineering."],"dc:title":["Investigation of velocity gradient as driving force of flow pulsation in fuel assemblies"],"dc:type":["Thesis"]},"updated_at":"2026-07-22T22:22:24Z"}