Modeling Intrajunction Dispersion at a Well-Mixed Tidal River Junction

AbstractThe 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...

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Veröffentlicht in:Journal of hydraulic engineering (New York, N.Y.) N.Y.), 2016-08, Vol.142 (8)
Hauptverfasser: Wolfram, Phillip J, Fringer, Oliver B, Monsen, Nancy E, Gleichauf, Karla T, Fong, Derek A, Monismith, Stephen G
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Sprache:eng
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Zusammenfassung:AbstractThe 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.
ISSN:0733-9429
1943-7900
DOI:10.1061/(ASCE)HY.1943-7900.0001108