Laboratory Effects in Beach Studies. Volume V. Movable-Bed Experiment with H sub o/L sub o = 0.039.
COASTAL ENGINEERING RESEARCH CENTER FORT BELVOIR VA
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In an experiment with a wavelength of 10.26 feet wave period 1.50 seconds on an initial movable-bed slope of 0.10 in a tank 10 feet wide with waves directed normal to the initial shoreline, the foreshore and inshore changes of the profile were three-dimensional to such an extent that a longshore current developed at the base of the foreshore. Comparable experiments in the same facility, but with a longer wavelength, did not show three-dimensional effects to as great an extent. As a working hypotehsis, it is proposed that the shorter the wavelength in a movable-bed experiment relative to a given tank width, the greater the likelihood of three-dimensional effects in profile development. The wave steepness was higher than the wave steepness in the comparable earlier experiments 0.039 versus 0.021 in Vols. II, III, and IV of the series, and the reflection coefficient was lower, as would be expected from increased breaker dissipation of steeper waves and for a shorter wave on the same slope. Variations in the reflection coefficient may have been caused by the change in phase difference between the waves reflected from the offshore slope and the foreshore slope as those two zones moved farther apart on the developing profile. The profile appeared to have almost attained an equilibrium shape after 150 hours, in contrast to the comparable experiments with lower wave steepness, which were not approaching equilibrium after a much longer time in the same facility. Author
- Physical and Dynamic Oceanography
- Test Facilities, Equipment and Methods