A temporal and spatial analysis of wave–generated foam patterns in the surf zone
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Authors
Benbow, Charlotte A.
Subjects
Wave Breaking
Foam
Obliquely Descending Eddies
Aerial Imagery
Image Processing
Foam
Obliquely Descending Eddies
Aerial Imagery
Image Processing
Advisors
MacMahan, Jamie
Date of Issue
2015-12
Date
Dec-15
Publisher
Monterey, California. Naval Postgraduate School
Language
Abstract
Aerial videos of the surf zone at Sand City, Monterey Bay, CA, were acquired using an unmanned aerial vehicle. Videos of 26 individual bores were converted to still images and were georectified, georeferenced, and post processed. The size, shape, and evolution of the wave generated foam patterns within the surf zone were analyzed. The results were tested against two existing hypotheses of foam pattern generation, Obliquely Descending Eddies (ODEs) and self-organization due to bubble rise. Three foam regions within the surf zone were recognized. The largest region, the foam mat, encompasses nearly the entire surf zone and is described as a mat of foam that develops obvious foam holes. The areas of the holes grew in area and elongated with time. The results were inconsistent with the two theories of foam hole generation. The fringe region is the most seaward foam region and is marked with circular foam rings that become larger in area and more distinct with time. The fringe region data are contrary to observations of ODEs but is consistent with the theory of self-organization due to bubble rise. The gap region, located between the plunge point and the splash up created by the bore collapse, is marked by horizontal foam tubes oriented in the cross-shore direction. The foam tubes are likely created in the convergent region between two counter-rotating vortices.
Type
Thesis
Description
Reissued 10 Jan 2017 with corrected degree.
Series/Report No
Department
Oceanography
Oceanography
Organization
Identifiers
NPS Report Number
Sponsors
Funder
Format
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.