Title:
Observations of Laboratory Rip Currents

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dc.contributor.advisor Haas, Kevin A.
dc.contributor.author Sapp, Brian Keith en_US
dc.contributor.committeeMember Fritz, Hermann
dc.contributor.committeeMember Webster, Donald
dc.contributor.committeeMember Work, Paul
dc.contributor.department Civil and Environmental Engineering en_US
dc.date.accessioned 2006-06-09T18:01:25Z
dc.date.available 2006-06-09T18:01:25Z
dc.date.issued 2006-01-17 en_US
dc.description.abstract Laboratory experiments of rip current systems are performed in a wave basin with a bar and rip channel geometry at the Ocean Engineering Laboratory at the University of Delaware. The experiments include both in situ water level and velocity measurements and optical visualization of the flow field under a variety of normal-incident wave conditions. Digital video is used to record surface drifters moving through a rip current system. A method is presented that tracks these digitally-recorded drifters into long Lagrangian sequences. The laboratory measurements capture both an Eulerian and Lagrangian description of the rip current system. Time-averaged rip current properties are calculated and analyzed using both in situ and video measurements. From the video, Lagrangian velocities are computed with forward differencing of the low-pass filtered drifter tracks. Wave properties are also estimated using the orbital drifter motions and linear (Airy) wave theory. The effects of various wave conditions on the time-averaged rip current systems are investigated to show that wave height is a critical parameter. Measurements of circulation cells are obtained by spatially averaging the drifter track velocity measurements into a polar grid ranging from 0.25 m to 3.25 m from the center of the cell. Circulation cell features, such as the center of circulation and cell width, are calculated to characterize their response to various wave conditions. Spectral analyses are used to characterize the rip current pulsations in the experimental measurements. Three frequencies are found to be energetic in several of the experiments in the low frequency band: the wave group frequency, a lower frequency, and the interaction of the wave group and lower frequencies. Some experiments have significant energy at each of the three peaks, where others have only one or none. The lower frequency motions have also been found in the video measurements and attributed to rip meandering. Possible causes for the low-frequency pulsations, including wave basin seiching, circulation cell instabilities, and wave-current interaction, are discussed. This thesis adds to previous rip current studies by providing a spatially-large and time-varying perspective of rip current systems as a whole. en_US
dc.description.degree M.S. en_US
dc.format.extent 3359329 bytes
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/10453
dc.language.iso en_US
dc.publisher Georgia Institute of Technology en_US
dc.subject Laboratory en_US
dc.subject Pulsations
dc.subject Video tracking
dc.subject Rip current
dc.subject Circulation cell
dc.subject Meandering
dc.subject.lcsh Ocean currents en_US
dc.title Observations of Laboratory Rip Currents en_US
dc.type Text
dc.type.genre Thesis
dspace.entity.type Publication
local.contributor.advisor Haas, Kevin A.
local.contributor.corporatename School of Civil and Environmental Engineering
local.contributor.corporatename College of Engineering
relation.isAdvisorOfPublication b89a440b-33e2-469d-914c-da1887bf6484
relation.isOrgUnitOfPublication 88639fad-d3ae-4867-9e7a-7c9e6d2ecc7c
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
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