Effects of Velocity Gradients and Secondary Flow on the Dispersion of Solutes in a Meandering Channel
Publication: Journal of Hydraulic Engineering
Volume 132, Issue 12
Abstract
Two contrasting mechanisms, created by channel curvature which strongly affect longitudinal dispersion of solutes in rivers are examined. In natural channels the large cross-sectional variability of the primary velocity component tends to increase longitudinal dispersion by providing a large difference between adjacent fast and slow moving zones of fluid. By contrast secondary circulation tends to decrease longitudinal dispersion by enhancing transverse mixing. A series of tests have been carried out in a very large flume containing a meandering water-formed sand bed channel to measure the longitudinal dispersion coefficient at various locations around a meander. These experimental observations are compared with experimental data obtained from meandering channels with smooth, fixed sides and regular cross-sectional shapes. All the data has been compared against predictions from two current modeling approaches. Finally, the significance of the two competing mechanisms in curved channels is discussed with regard to their relative influence on longitudinal mixing.
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Acknowledgments
The experiments on the Flood Channel Facility were executed under a research project granted to the first writer by the EC Commission, Directorate General for Science, Research and Development as part of the program Training and Mobility of Researchers, Large Scale Facilities, under Control No. ERB FGME CT95 0082. Data analysis has been partially funded by the Italian National Research Council (CNR), National Group on Chemical-Industrial and Environmental Hazards and by CO.RI.LA (Consortium for Research on Venice Lagoon). The writers thank Dr. Jobie Boxall and Dr. Ian Guymer for technical support and valuable discussions, Professor Stefano Lanzoni for his suggestions on model. Mrs. Paola Trevisan and Mrs. Elena Romano contributed to the experimental work. The writers are also thankful to Dr. Roger Bettess and Dr. Jesper Damgaard for coordinating the activity on the facility.
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Information
Published In
Journal of Hydraulic Engineering
Volume 132 • Issue 12 • December 2006
Pages: 1295 - 1302
Copyright
© 2006 ASCE.
History
Received: Oct 20, 2004
Accepted: Jun 6, 2006
Published online: Dec 1, 2006
Published in print: Dec 2006
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