Graduation Year

2015

Document Type

Dissertation

Degree

Ph.D

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Civil Engineering

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Andrés E. Tejada-Martínez, Ph.D.

Co-Major Professor

Daniel C. Simkins, Jr., Ph.D.

Committee Member

Daniel C. Simkins, Jr., Ph.D.

Committee Member

Muhammad M. Rahman, Ph.D.

Committee Member

Mark Luther, Ph.D.

Committee Member

Boris Galperin, Ph.D.

Keywords

LES, numerical simulation, ocean modeling, surface cooling, vertical mixing

Abstract

In a shallow shelf region, turbulent motion can have a major effect on coastal processes including ecosystem functioning, surface gas exchange and sediment resuspension. Many factors contribute to such turbulence; wind and wave forcing, buoyancy induced by surface heat fluxes and tidal forcing all play a key role in generating vertical mixing in this shallow region. Alongside these independent sources of turbulence, combinations thereof can lead to full-depth turbulent structures acting secondary to the mean flow and leading to enhanced vertical mixing throughout the entire water column.

Field and laboratory experiments can often prove to be costly and time consuming, and reproducing or maintaining the complex flow dynamics of real world ocean flows is a constant challenge to these methods of research. As such, those interested in developing realistic and useful models of the marine environment to further understand its behavior often rely on 3-dimensional mathematical modeling and simulation. In this dissertation, simulations will be presented of turbulent flow and associated vertical mixing in a domain representative of the shallow coastal ocean, sufficiently far off shore that the land-ocean boundary does not significantly affect the flow behavior. This will be done using a large-eddy simulation (LES) method; solving the governing Navier-Stokes equations over a finite grid designed to capture the large, energy containing turbulent scales, and modeling the smaller, sub-grid scales.

The simulations to be presented feature combinations of coastal forcing mechanisms which are either presently unexplored or the analysis of which has been hindered by the complexity of field measurements and the challenge of isolating independent causes of turbulent motion. This will include surface heat fluxes, tidal forcing and Langmuir (or wave) forcing, acting both in isolation and in conjunction with each other, in order to bridge existing gaps in knowledge and provide a more complete understanding of the generation of full-depth turbulent structures in this shallow coastal water column.

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