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You searched for subject:(density driven circulation). Showing records 1 – 2 of 2 total matches.

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Delft University of Technology

1. Pubben, S.G.T. (author). 3D Mixing patterns in San Francisco South Bay.

Degree: 2017, Delft University of Technology

Estuaries are complex systems that show a variety of hydrodynamic conditions. These conditions are influenced by bathymetry, geometry, climate characteristics, interacting fresh and salt water flows, and mixing effects caused by winds and wind-waves. The interaction between fresh and salt water flows in combination with mixing effects caused by wind and waves give rise to spatial and temporal varying salinity and temperature fields. Gradients in these fields can give rise to density driven circulation. These density driven currents play an important role in sediment circulation and water quality properties of estuaries. This research focuses on density driven circulation patterns in complex estuarine systems, in which San Francisco South Bay (SFSB) presents an interesting and excellent case study. SFSB can be considered as a unique estuarine system that is influenced by both far-field and local fresh water sources during periods of high fresh water inflow. Fresh water inflow from local sources causes a classic estuarine circulation with a lower salinity landward. In contrast, peak fresh water flows from the far-field sources enter SFSB through the same inlet as through which ocean water enters SFSB, which is exceptional in an estuarine system. As a result, SFSB changes in a reverse estuary, which is normally only found in regions where evaporation rates exceed precipitation and fresh water inflow so that the estuary becomes saltier than the ocean. The research objective of this thesis is to understand the circulation pattern and density dynamics in SFSB, caused by spatial and temporal gradients in salinity and temperature. A 3D process-based model, Delft3D FM, is set up in order to simulate the influences of fresh water, tide and wind, referred to as the driving forces, on the density driven circulation in SFSB. Model results showed that the main drivers of estuarine circulation in SFSB are the tide and the frehs water inflow. The influence of the wind on the density driven circulation is negligilbe. Additionally, it is found that the influence of salinity is dominant over the influence of water temperature on the water density in SFSB. During the majority of the year the fresh water inflow is low. As a result, SFSB is well mixed and a classic estuarine circulation can be observed. However, peaks in fresh water from far-field fresh water sources can drive a temporal reverse estuarine circulation in SFSB. The reverse estuarine circulation and stratification are found to be restricted to the main channel of SFSB. In addition, it is found that the amount of fresh water that originates from the far-field fresh water sources determines the extent of which reverse estuarine circulation can be observed in SFSB.

Civil Engineering and Geosciences

Hydraulic Engineering

Advisors/Committee Members: Uijttewaal, W.S.J. (mentor), Labeur, R.J. (mentor), Katsman, C. (mentor), van der Wegen, M. (mentor).

Subjects/Keywords: Delft3D FM; San Francisco Bay; hydrodynamics; density driven circulation; estuary

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Pubben, S. G. T. (. (2017). 3D Mixing patterns in San Francisco South Bay. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:d5ca021e-8652-41f8-b91a-5c2bccdb777e

Chicago Manual of Style (16th Edition):

Pubben, S G T (author). “3D Mixing patterns in San Francisco South Bay.” 2017. Masters Thesis, Delft University of Technology. Accessed October 21, 2020. http://resolver.tudelft.nl/uuid:d5ca021e-8652-41f8-b91a-5c2bccdb777e.

MLA Handbook (7th Edition):

Pubben, S G T (author). “3D Mixing patterns in San Francisco South Bay.” 2017. Web. 21 Oct 2020.

Vancouver:

Pubben SGT(. 3D Mixing patterns in San Francisco South Bay. [Internet] [Masters thesis]. Delft University of Technology; 2017. [cited 2020 Oct 21]. Available from: http://resolver.tudelft.nl/uuid:d5ca021e-8652-41f8-b91a-5c2bccdb777e.

Council of Science Editors:

Pubben SGT(. 3D Mixing patterns in San Francisco South Bay. [Masters Thesis]. Delft University of Technology; 2017. Available from: http://resolver.tudelft.nl/uuid:d5ca021e-8652-41f8-b91a-5c2bccdb777e


Delft University of Technology

2. van Kempen, Oxana (author). Sediment pathways in San Francisco South Bay.

Degree: 2017, Delft University of Technology

This study aims for a better understanding of the sediment pathways in San Francisco South Bay (South Bay). Many issues relevant to the Bay Area community such as shipping, recreational and commercial fishing, habitat restoration, human health, and environmental water quality are reliant on understanding sediment pathways (McKee et al. [2006]). Existing theories suggest that the Sacramento-San Joaquin Delta deliver sediment to South Bay during periods of high river flows. Different hydrodynamic forces, such as the tide, wind and baroclinic flows, redistribute these sediments around South Bay. In this research, trends are analysed using a new set of data (WY2015-WY2017) and sediment pathways in time and space are investigated using a 3D numerical model. In this model, the pathways of three sediment classes with different settling velocities are traced from their source throughout the Bay Area. No such study has yet been undertaken in the South Bay Area. There is a high Delta sediment input to South Bay during periods of high river flow. The local tributaries contribute only marginally to the suspended sediment concentration of South Bay. With a decreasing sediment load from the Delta, the importance of the local tributaries as a sediment source for South Bay could increase. In this research, three different types of sediment exchange between Central Bay and South Bay are observed. The first type is observed during periods of low river flows (Q < 800m3/s). A seaward directed residual flow is found in the channel at Bay Bridge. Sediments are slowly transported out of South Bay. The second type is observed after a period of moderate river flow (Q > 800m3/s). A pulsed sediment flux from the Delta increases the turbidity of Central Bay, resulting in a horizontal spatial variation in SSC from Central Bay to South Bay. The diffusive character of the tide transports the sediments slowly from the turbid Central Bay to the relatively clearer South Bay. The third sediment exchange type is observed after an extreme Delta river flow (QDel ta È 5000m3/s)). The extreme Delta flow refreshes a large part of Central Bay and South Bay. The salinity of Central Bay increases slowly, resulting in a substantially more saline Central Bay than South Bay for a couple of months. The resulting baroclinic flow transports the sediments from Central Bay into South Bay through the landward directed bottom current. Two dominant pathways with opposite transport direction characterise the sediment transport in South Bay. One pathway is located in the channel and is directed southward during periods of high river runoff. The second pathway is located on the extensive east flat and is directed northward during periods of high river runoff. The transport in the channel is dominant during the wet period, resulting in a net transport landward. Besides these two dominant pathways, four re-circulations cells are found, facilitating the exchange between the channel and the shoals. The next step in gaining more insight into the sediment physics is a model… Advisors/Committee Members: Pietrzak, Julie (mentor), Wang, Zhengbing (mentor), van Maren, Bas (mentor), van der Wegen, Mick (mentor), Delft University of Technology (degree granting institution).

Subjects/Keywords: San Francisco Bay; San Francisco South Bay; Sediment pathways; density driven circulation; Delft3D-FM

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

van Kempen, O. (. (2017). Sediment pathways in San Francisco South Bay. (Masters Thesis). Delft University of Technology. Retrieved from http://resolver.tudelft.nl/uuid:e219bed5-cee3-42ba-a2f8-571539b1d66f

Chicago Manual of Style (16th Edition):

van Kempen, Oxana (author). “Sediment pathways in San Francisco South Bay.” 2017. Masters Thesis, Delft University of Technology. Accessed October 21, 2020. http://resolver.tudelft.nl/uuid:e219bed5-cee3-42ba-a2f8-571539b1d66f.

MLA Handbook (7th Edition):

van Kempen, Oxana (author). “Sediment pathways in San Francisco South Bay.” 2017. Web. 21 Oct 2020.

Vancouver:

van Kempen O(. Sediment pathways in San Francisco South Bay. [Internet] [Masters thesis]. Delft University of Technology; 2017. [cited 2020 Oct 21]. Available from: http://resolver.tudelft.nl/uuid:e219bed5-cee3-42ba-a2f8-571539b1d66f.

Council of Science Editors:

van Kempen O(. Sediment pathways in San Francisco South Bay. [Masters Thesis]. Delft University of Technology; 2017. Available from: http://resolver.tudelft.nl/uuid:e219bed5-cee3-42ba-a2f8-571539b1d66f

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