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ERIC Number: ED526596
Record Type: Non-Journal
Publication Date: 2009
Pages: 193
Abstractor: As Provided
Reference Count: N/A
ISBN: ISBN-978-1-1095-7951-2
ISSN: N/A
Bed Morphology and Sediment Transport under Oscillatory Flow
Pedocchi Miljan, Francisco
ProQuest LLC, Ph.D. Dissertation, University of Illinois at Urbana-Champaign
Recent laboratory and field experiments have shown the inability of existing oscillatory flow ripple predictors to accurately predict both ripple size and planform geometry. However, at this time, only partial adaptations of these predictors have been proposed in the literature to account for the observed discrepancies with experimental data obtained after the publication of these predictors. This work presents a comprehensive dataset compiled from twenty seven literature studies and our new experimental data. Dimensional analysis is used both to clarify the importance of the different variables involved in the development of ripples and to generate the basic dimensionless framework for the study of ripple morphology under oscillatory flow. This includes the development of a revised formulation for the oscillatory flow friction coefficient in the transition from hydraulically rough to smooth regimes. Several ripple size and planform geometry predictors are contrasted against the compiled dataset. New predictors for ripple wavelength and height are proposed as well as a new predictor for the planform geometry. This new predictors overcome several of the limitations found in earlier predictors. The new predictors emphasize the existence of local and global sediment transport mechanisms over a ripple bed, each of them acting at different scales. In particular, sediment size is found to have an important effect on the size and geometry of bedforms that can be generated under oscillatory flows. Our new large scale experimental data was obtained in the Large Oscillatory Water-Sediment Tunnel (LOWST) at the Hydrosystems Laboratory of the University of Illinois at Urbana-Champaign. As part of this work several measuring devices have been installed in the LOWST, and the required data acquisition and post-processing tools have been developed. The installed equipment includes: a Sontek Micro Acoustic Doppler Velocimeter, a pressure transducer, an Ultrasonic Velocity Profiler (Met-Flow UVP-DUO), a peristaltic pump, and a in-house adapted pencil beam sonar. The experiments focused on two aspects of the bed morphology: the study of the ripple planform geometry under a broad range of flow conditions, and the effect of orbital velocities on the ripple size under long water excursions. Regarding the planform geometry of the ripples, the results showed that narrow facilities restrict the three-dimensional development of bedforms. For the case of the long water excursion experiments, the ripple size was found to initially decrease as the maximum orbital velocity was increased, as it has been reported by other authors. However, as the maximum orbital velocity was further increased anorbital ripples did not develop and instead the ripples started to increase their size. These last ripples had round crests, and do not seem to belong to the same bedform class as the sharp crested ripples usually reported in the literature. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]
ProQuest LLC. 789 East Eisenhower Parkway, P.O. Box 1346, Ann Arbor, MI 48106. Tel: 800-521-0600; Web site: http://www.proquest.com/en-US/products/dissertations/individuals.shtml
Publication Type: Dissertations/Theses - Doctoral Dissertations
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
Identifiers - Location: Illinois