Multiscale numerical simulations of a complex macrotidal tidal-river estuary
Abstract/Contents
- Abstract
- Modern field-scale numerical models of estuaries have become widely used to study estuarine dynamics and to assess the impacts of engineering projects on estuaries. While current estuarine models focus primarily on the large-scale tidal dynamics, the model developed in the present study applies higher resolution than pre-existing models to capture the multiscale physics in a realistic estuary (the Snohomish River estuary). The scales range from tidally-driven variability in free surface, velocity and salinity in the estuary to the local-scale interaction of the tidal flow with an abrupt sill that has a dimension of roughly 10 m by 100 m. The model is developed using the SUNTANS solver and employs the Eulerian-Lagrangian Method (ELM) for advection of momentum for improved stability in the presence of substantial wetting and drying. The unstructured mesh extends more than 20 km to cover the advection of the salinity front, while the finest resolution applied around the sill is on the order of meters. Model predictions of free surface, currents and salinity are in good agreement with field measurements. Sensitivity analysis shows that the bathymetry of the intertidal mudflats across the bypass is critical for accurate prediction of the circulation around the sill, while bottom drag, advection of momentum, and fresh river inflow has a smaller and limited effect on the tidal flows. The performance of several two-equation turbulence closure models (k-kl, k-epsilon and k-omega) and stability functions (KC and CA) in predicting mixing and stratification is evaluated via the generic length scale (GLS) approach, and it shows small differences between the closure models. The model robustly obtains reasonable temporal and spatial mixing patterns in the estuary at different stages of a tidal cycle. A quadratic interpolation method is implemented for ELM following the framework in Walters et al. (2007), and both an idealized backward-facing step test case and field-scale simulations show improved accuracy and reduced diffusion and dissipation with the quadratic interpolation. When the quadratic interpolation is implemented with a fine mesh that incorporates 1 m resolution around the sill, the model captures the recirculating eddies downstream of the sill observed during ebb tides, and the velocity structures along a cross-channel transect close to the sill compare favorably to measurements. Finally, the highly variable local salinity field resulting from the interaction of the sill with the advection of the salinity front is discussed based on model results.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2011 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Wang, Bing |
|---|---|
| Associated with | Stanford University, Civil & Environmental Engineering Department. |
| Primary advisor | Fringer, Oliver B. (Oliver Bartlett) |
| Primary advisor | Street, Robert L |
| Thesis advisor | Fringer, Oliver B. (Oliver Bartlett) |
| Thesis advisor | Street, Robert L |
| Thesis advisor | Monismith, Stephen Gene |
| Thesis advisor | Stacey, Mark (Mark T.) |
| Advisor | Monismith, Stephen Gene |
| Advisor | Stacey, Mark (Mark T.) |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Bing Wang. |
|---|---|
| Note | Submitted to the Department of Civil and Environmental Engineering. |
| Thesis | Ph. D. Stanford University 2011 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Bing Wang
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