Investigations into the characteristics and underlying mechanism
of the circulation of water near the shore are reported. The two
main types of circulation, one a cellular system resulting from
Haves propagated nearly normally to the shore, and the other an
essentially alongshore flow associated with oblique waves, are
treated separately.
The cellular circulation studies were made in the field at
Virginia Beach and more extensively in wave tanks. From the field
experiments data were collected about the dimensions of the cells,
the way in which the Hater circulated, the rate of exchance of surf
zone water and the extent of recycling. A method for measuring the
changes in the mean sea level over intervals of time greater than
those of the wave periods, was developed. The model experiments
carried out in uniform wave tanks showed that the cellular circulations could be well simulated. Measurements were made of
the cell dimensions, the velocity of the longshore and rip currents,
and of the recycling regime.
A finding from the wave tank studies Has the presence of standing
waves formed by transverse edge waves. The interaction of these
standing waves with the gene rated waves normal to the shore could
be the initial cause of rip currents and the cellular circulation.
Studies of the alongshore system were made in the field only.
A method for measuring the volume of flow of longshore currents
was developed, tested, and applied. Calculated volumes of flow
using a theory based on continuity and the solitary wave theory
(as proposed by Inman and Bagnold) compared tolerably well with the
field observations. The calculations of volume of flow required a
knowledge of the wave height spectra in the surf. This was
established by making wave height recordings in the between-breaker
zone . It was found that the characteristics of the spectra
compared reasonably well with those pr e dict ed by the Longuet-Higgins
theory, previously assumed to apply to deep water waves only.
A mechanism for the transition from cellular to alongshore system is proposed. / Thesis (Ph.D.)-University of Natal, 1967.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/11035 |
| Date | January 1967 |
| Creators | Harris, Thomas Frank Wyndham. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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