Modeling Intrajunction Dispersion at a Well-Mixed Tidal River Junction
Publication: Journal of Hydraulic Engineering
Volume 142, Issue 8
Abstract
The relative importance of small-scale, intrajunction flow features such as shear layers, separation zones, and secondary flows on dispersion in a well-mixed tidal river junction is explored. A fully nonlinear, nonhydrostatic, and unstructured three-dimensional (3D) model is used to resolve supertidal dispersion via scalar transport at a well-mixed tidal river junction. Mass transport simulated in the junction is compared against predictions using a simple node-channel model to quantify the effects of small-scale, 3D intrajunction flow features on mixing and dispersion. The effects of three-dimensionality are demonstrated by quantifying the difference between two-dimensional (2D) and 3D model results. An intermediate 3D model that does not resolve the secondary circulation or the recirculating flow at the junction is also compared to the 3D model to quantify the relative sensitivity of mixing on intrajunction flow features. Resolution of complex flow features simulated by the full 3D model is not always necessary because mixing is primarily governed by bulk flow splitting due to the confluence–diffluence cycle. Results in 3D are comparable to the 2D case for many flow pathways simulated, suggesting that 2D modeling may be reasonable for nonstratified and predominantly hydrostatic flows through relatively straight junctions, but not necessarily for the full junction network.
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Acknowledgments
Support for this research was provided by the Delta Science Program and by the Department of Defense through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program. Special thanks to Jon Burau and the USGS California Water Science Center team for their help in the field. USGS/DWR discharge, stage, and bathymetry data was generously provided by Patricia Orlando (USGS), Brad J Sullivan (USGS), Joel Dudas (DWR), and Wyatt Pearsall (DWR). Advice of EMFL colleagues Sean Vitousek, Bobby Arthur, Matt Rayson, Joel Weitzman, and Ed Gross was invaluable in conducting this study. The authors also thank two anonymous reviewers, an anonymous Associate Editor, and Chief Editor Prof. Thanos Papanicolaou whose comments greatly improved the quality of the manuscript.
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Information & Authors
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Published In
Journal of Hydraulic Engineering
Volume 142 • Issue 8 • August 2016
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Nov 3, 2014
Accepted: Sep 16, 2015
Published online: Apr 6, 2016
Published in print: Aug 1, 2016
Discussion open until: Sep 6, 2016
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