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E. Eric Adams. Gensheimer, Robert James, III Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. Massachusetts Institute of Technology. Department of Civil and Environmental Engineering 2011-01-26T14:11:42Z 2011-01-26T14:11:42Z 2010 2010 http://hdl.handle.net/1721.1/60709 695587421 Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010. 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 (p. 255-259). Open-water sediment disposal is used in many applications around the world, including land reclamation, dredging, and contaminated sediment isolation. Timely examples include the land reclamation campaign currently underway in Singapore and the Boston Harbor Navigation Improvement Project. Both of these projects required the precise dumping of millions of cubic meters of purchased sediment, in the former example, and dredged material (both clean and contaminated), in the latter example. This shows the significant economic and environmental interests in the accurate placement of sediment, which requires knowledge of how particle clouds behave in ambient currents. Flow visualization experiments were performed in a glass-walled recirculating water channel to model open-water sediment disposal by releasing particles quasi-instantaneously into the channel with ambient currents. For releases at the surface, criteria were developed to characterize ambient currents as "weak," "transitional," or "strong" as a function of particle size. In "weak" ambient currents, particle clouds advected downstream with a velocity equal to the ambient current, but otherwise the behavior and structure was similar to that in quiescent conditions. The parent cloud's entrainment coefficient (??) increased with decreasing particle size and elevation above the water surface, between values of 0.10 and 0.72, but for most experiments, the range was less significant (0.11 to 0.24). A substantial portion of the mass initially released, up to 30 %, was not incorporated into the parent cloud and formed the trailing stem. This was also heavily dependent on the initial release variables, with the greatest sensitivity on particle size. The "loss" of sediment during descent, defined as the fraction of mass missing a designated target with a radius equal to the water depth, was quantified and found to increase sharply with current speed. The cloud number (Nc), which relates the particle settling velocity to a characteristic thermal descent velocity, provides a basis for scaling laboratory results to the real world and formulating guidelines to reduce the losses that could result from open-water sediment disposal. by Robert James Gensheimer, III. S.M. 259 p. eng Massachusetts Institute of Technology M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 Civil and Environmental Engineering. Dynamics of particle clouds in ambient currents with application to open-water sediment disposal Thesis application/pdf Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="db9525d7-6be6-4d4c-91fa-420d9a9a158a"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Dynamics of particle clouds in ambient currents with application to open-water sediment disposal</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2010</PublicationDate> <Authors> <Author> <DisplayName>Gensheimer, Robert James, III</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Civil and Environmental Engineering.</Keyword> <Abstract>Open-water sediment disposal is used in many applications around the world, including land reclamation, dredging, and contaminated sediment isolation. Timely examples include the land reclamation campaign currently underway in Singapore and the Boston Harbor Navigation Improvement Project. Both of these projects required the precise dumping of millions of cubic meters of purchased sediment, in the former example, and dredged material (both clean and contaminated), in the latter example. This shows the significant economic and environmental interests in the accurate placement of sediment, which requires knowledge of how particle clouds behave in ambient currents. Flow visualization experiments were performed in a glass-walled recirculating water channel to model open-water sediment disposal by releasing particles quasi-instantaneously into the channel with ambient currents. For releases at the surface, criteria were developed to characterize ambient currents as "weak," "transitional," or "strong" as a function of particle size. In "weak" ambient currents, particle clouds advected downstream with a velocity equal to the ambient current, but otherwise the behavior and structure was similar to that in quiescent conditions. The parent cloud's entrainment coefficient (??) increased with decreasing particle size and elevation above the water surface, between values of 0.10 and 0.72, but for most experiments, the range was less significant (0.11 to 0.24). A substantial portion of the mass initially released, up to 30 %, was not incorporated into the parent cloud and formed the trailing stem. This was also heavily dependent on the initial release variables, with the greatest sensitivity on particle size. The "loss" of sediment during descent, defined as the fraction of mass missing a designated target with a radius equal to the water depth, was quantified and found to increase sharply with current speed. The cloud number (Nc), which relates the particle settling velocity to a characteristic thermal descent velocity, provides a basis for scaling laboratory results to the real world and formulating guidelines to reduce the losses that could result from open-water sediment disposal.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>