HCNSO Student Theses and Dissertations

Defense Date

12-5-2018

Document Type

Dissertation

Degree Name

Ph.D. Oceanography/Marine Biology

First Advisor

Alexander Soloviev, Ph.D.

Second Advisor

Tracey Sutton, Ph.D.

Third Advisor

John Holmes, Ph.D.

Fourth Advisor

Tamay Ozgokmen, Ph.D.

Abstract

Small- and fine-scale biological and oceanographic processes may have a measurable electromagnetic signature. These types of processes inherently involve turbulence and three-dimensional dynamics. Traditional models of the electromagnetic signature of oceanographic processes are of an analytical nature, do not account for three-dimensional boundary layer dynamics or turbulence, self-inductance, and may not describe the variety of the environmental conditions occurring in the ocean. In order to address this problem, I have implemented magnetohydrodynamic (MHD) computational fluid dynamics (CFD) tools, which has allowed for the evaluation of the electromagnetic signature of a number of small- and fine-scale biological and oceanographic processes in the ocean. The suite of computational tools has included the commercial models ANSYS Fluent, coupled with the MHD module, and ANSYS Maxwell. These computational tools have been well-established in fluid and electromagnetic engineering. The application of CFD and MHD tools in oceanography is new but is undergoing rapid development. In this work, substantial effort was made toward the CFD, MHD, and magnetostatic model verification and identification of model limitations. Verifications of the CFD, MHD, and magnetostatic models were conducted by successfully comparing their results with the field measurements and laboratory experiments.

Comparison with the traditional (analytical) models for surface and internal waves, has revealed their limitations related to bottom boundary layer physics, effect of self-inductance, and, to a lesser extent, the magnetic permeability difference at the air-sea interface. These limitations become important for shallow water internal waves. As a result, the traditional models significantly overestimate the magnetic signature of internal waves observed at the Electromagnetic Observatory.

After model verification with the field and laboratory data, the computational models were then applied to evaluate the magnetic signature of diel vertical migration (DVM) of zooplankton, surface waves, internal wave solitons, freshwater lens spreading, and Langmuir circulation. The quantitative estimates have been made for typical environmental conditions. In other environmental conditions, their magnetic signature may be somewhat different. The suite of computational models developed in this dissertation work allows for the estimation of the magnetic signature of fine- and small-scale oceanographic processes in virtually any environmental conditions (e.g., in oil emulsions). I anticipate the result of this study will have Naval, environmental, and oil exploration applications.

ORCID ID

https://orcid.org/0000-0002-2743-3602

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