EXPLORING TURBULENT WAKES IN A NON-UNIFORMLY STRATIFIED ENVIRONMENT FOR SUBMARINE DETECTION
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Authors
Nadaf, Elias d.
Subjects
wake dynamics
non-linear stratification
kinetic energy
thermal energy
dissipation rate of kinetic energy
dissipation rate of thermal variance
epsilon parameter
chi parameter
variations in temperature field
numerical modeling
openfoam
submarine detection
no acoustic means detection
internal waves reflection
Froude number
high-resolution numerical simulation
wake core position
non-linear stratification
kinetic energy
thermal energy
dissipation rate of kinetic energy
dissipation rate of thermal variance
epsilon parameter
chi parameter
variations in temperature field
numerical modeling
openfoam
submarine detection
no acoustic means detection
internal waves reflection
Froude number
high-resolution numerical simulation
wake core position
Advisors
Radko, Timour
Brown, Justin M.
Date of Issue
2022-06
Date
Publisher
Monterey, CA; Naval Postgraduate School
Language
Abstract
This study aims to explore the behavior of turbulent wakes generated by a spherical submerged body propagating with constant speed in a non-uniformly stratified fluid. The investigation is based on a series of high-resolution numerical simulations in which the background stratification is systematically varied. We consider one linear and five non-linear temperature profiles and two sets of Froude numbers (Fr), Fr = 1.0 and Fr = 3.2. The analysis of dissipation of thermal variance (χ) shows that the shape of the wake for non-uniform profiles is more horizontally spread, and internal waves are much stronger than in linear stratification. Experiments with Fr = 1.0 show a rather asymmetric energy distribution caused by internal wave reflections from low-gradient regions. An idealized model demonstrates that internal waves emitted at horizontal angles shallower than roughly 64 degrees are reflected. For Fr = 3.2, internal waves are radiated at steeper angles and transmitted more. Using decay rates of χ, the maximum detection time of the wake can be estimated, showing that for Fr = 3.2, the thermal signal lasts four to five times longer than for Fr = 1.0. Furthermore, concave profiles produce signals lasting approximately twice as long as those for linear profiles, whereas low-gradient types have half the duration. This research is expected to assist in the development of non-traditional detection algorithms for undersea warfare.
Type
Thesis
Description
Series/Report No
Department
Oceanography (OC)
Organization
Identifiers
NPS Report Number
Sponsors
Office of Naval Research, 875 North Randolph Street, Arlington, VA 22203
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Citation
Distribution Statement
Approved for public release. Distribution is unlimited.
Rights
Copyright is reserved by the copyright owner.