Journal of Waterway, Port, Coastal, and Ocean Engineering

Hunt’s equation provides a simple means of estimating the runup of breaking waves. However, breaking waves also induce setup on a slope. A modification to Hunt’s equation is advocated which accounts for the presence of wave setup. Support for the modification is provided by data from model tests involving random waves approaching smooth, impermeable slopes of 1:5, 1:10, 1:20, and 1:30. Coefficients to be used in the modified equation are given which allow the significant runup and other characteristic values to be estimated.

Power generation by tidal currents requires the establishment of a pressure difference across a turbine. This limits the power output to a fraction of the undisturbed energy flux through the same cross-sectional area, though the maximum possible value of this fraction is not well established. It is further shown that an array of turbines in the entrance to a bay is most effective if it is uniformly distributed across the entrance. The maximum power available for a quadratic drag law occurs when the tidal range inside the bay is reduced to 0.74 of the original amplitude, suggesting that power generation is compatible with the maintenance of good flushing and with use of the bay for other purposes. Moreover, this exploitation of tidal power through continuous operation of current turbines in the entrance is not much less productive than more conventional schemes that rely on trapping the water at high tide and releasing it during a small part of the tidal cycle.

Mudflat profiles were measured monthly along two cross-shore lines exceeding 1,000 m in the vicinity of a river mouth for 2 years. All the measured profiles are shown to be approximated within average errors of 3 cm by a quadratic profile with three parameters that vary with time. The temporal variations of the quadratic profile represented by the quadratic convexity, mean slope, and vertical displacement are correlated with available data on the tide level and range, significant wave height, wind speed, and river discharge in the vicinity of the field site. The vertical displacement varied in phase with the annual tide level variation of 40 cm, but the mudflat displacement was only 20% of the tide level displacement. The mudflat slope became gentler or steeper as the tide level rose or fell annually. The proposed quadratic profile approach may be useful in examining intertidal mudflat morphology at other sites.

In this paper, the wave transmission, reflection, and energy dissipation characteristics as well as the hydrodynamic forces of two partially submerged breakwaters are compared. The breakwaters under consideration are designed to be installed in coastal areas where the water depth may be important (typically 50 m), making traditional bottom seated configurations unsuitable. They are composed of a free-surface piercing caisson mounted on vertical piles. The first breakwater considered in this study, as a matter of reference for comparison, is a rectangular caisson. The second one is a new profile proposed by Colmard and called BYBOP by the writer. The seaside face, fronting the ocean, is an elliptic profile while the harbor side is a plane inclined 55° to the vertical. A numerical simulation on both these shapes, at model scale, was carried out in two numerical wave tanks. The first one, CANAL, is based on fully nonlinear potential flow theory while the second one, ICARE, is a Reynolds averaged Navier–Stokes equations solver simulating viscous free-surface flow around structures. The problem is considered as a two dimensional one and solved in the time domain. Reflection, transmission, and dissipation coefficients are computed, together with hydrodynamic forces, on the two different caisson shapes. The new design is shown to have far better efficiency, at less material expenses, for the same width.

Two series of shake table tests were performed in order to study the sliding displacement of caisson type quay walls and breakwaters due to earthquake motions. In the first series of the experiments, a gravity type caisson wall was modeled and a horizontal tension force was applied. Then, 20 cycles of sinusoidal waves with different amplitudes were applied as input accelerations. In the second series of the experiments, three caisson type composite breakwaters were tested with different water levels. Earthquake records observed in Hachinohe and Ofunato ports were used as input motion. The results show that the yield acceleration at the time that sliding tends to start and during the sliding is not a constant value and the yield acceleration decreases immediately after sliding. Test results show that considering single yield acceleration during the displacement analysis may lead to erroneous results. The comparison of the test and analysis results suggests the use of two-level yield accelerations as static and dynamic levels. The outcomes of the test results also reveal the drastic effect of rocking on triggering the sliding.

This study investigated the generation and propagation of water waves in a numerical viscous wave flume. The numerical scheme developed by Huang and collaborators for solving the unsteady two-dimensional Navier–Stokes equations for wavemaking problems was employed to generate different incident waves, including small- and finite-amplitude waves and solitary waves. The accuracy of the numerical results for the wave and velocity profiles was verified by comparison with the analytical solutions. The wave propagation in a numerical wave flume was also investigated. For periodic gravity waves on finite water depth, the results showed that waves with larger Ursell numbers are more stable than those with smaller Ursell numbers. The propagation of solitary waves in the channel is stable. For stable waves, the wave height attenuation caused by the energy dissipation in the wave motion was shown to be consistent with the theoretical results.