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Title: Oceanic boundary layers : a theoretical, numerical and laboratory approach
Author: Shravat, Amrita
ISNI:       0000 0004 2725 3286
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2012
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In this thesis, the behaviour of oceanic boundary layers is investigated via theoretical, numerical and laboratory studies. Some of the novel features of the next generation ocean model developed at Imperial College are tested. The process of separation of the western boundary currents is not fully understood. Over the years, there have been several theories to explain this process. However, none of these are complete and lack one or the other aspect of separation of western boundary currents. The triple-deck theory is extended to oceanography to provide a theoretical understanding for the competing effects of differential rotation and curvature. It was found that the differential rotation causes the flow to accelerate, while the curvature acts to decelerate the flow. The fate of the oceanic boundary layer lies on this competition. The Imperial College Ocean Model (ICOM) is employed to undertake numerical experi- ments to investigate the separation of western boundary currents further. The study exposes the various shortcomings of the ICOM, which as a result caused the investigation to be severely constrained. The idealised wind-driven barotropic model is used to assess some of the novel features of the ICOM and to understand the instabilities and their role on the separation of the western boundary current. Another idealised model is set-up with laboratory scales to examine the role of topography and the influence of Deep Western Boundary Current on the boundary current separation. It is found that the bottom boundary condition, the width of the continental shelf and the stratification play a significant role in boundary current separation from a sloping sidewall, in the modeled laboratory analogue. A laboratory study is undertaken to explore the energetics of a shear-driven stratified fluid in a cylinder. It is found that for moderate Richardson number, about half of the external energy is spent on mixing the fluid, while the other half goes into driving the mean flow.
Supervisor: Marshall, D. P. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available