Journal of Waterway, Port, Coastal, and Ocean Engineering

Nonlinear effects for wave groups in bimodal sea states are investigated. The linear free surface displacement is obtained by applying the quasi-determinism theory of the highest waves, with the spectrum given by the superposition of two JONSWAP spectra. Linear groups are modeled as the sum of two groups produced by each unimodal spectrum. Nonlinear effects are given as second-order contribution to the linear free surface displacement. The structure of wave groups is then analyzed for some bimodal spectra. The linear component of wave groups shows a strong variation with respect to the classical structure with unimodal spectra, particularly in mixed seas. It is observed that the nonlinearity gives small contributions for swell dominated seas. For wind dominated sea states, the main nonlinear contribution is given by the wind wave spectral components. For mixed sea states, the interaction among the components of the wind wave spectrum and the components of the swells could give a meaningful contribution to the nonlinear profile. The strongest nonlinear effects occur when the two peaks of the spectrum are close to each other. Finally, the results are validated by means of Monte Carlo simulations of nonlinear sea waves.

In shallow waterways such as the St. Lawrence River, an accurate prediction of the squat is important to ensure a balance between the security and the efficiency of traffic. The Canadian Coast Guard is now studying the squat phenomenon and considering to reassess the actual underkeel clearance standards of the St. Lawrence Waterway. Hence, a field campaign was conducted with 12 deep draft ship sailings, during which the maximal squat was measured with on-the-fly global positioning system. All the variables that may influence the squat (speed, draught, water level, etc.) were also measured. Twenty of the empirical models that are used in practice to predict the squat were tested and the Canadian Coast Guard recommended to either optimize these models or develop new models. Therefore, statistical approaches to model the squat of deep draft ships that navigate on the St. Lawrence Waterway are proposed in this paper. The Eryuzlu model, which is presently used by the Canadian Coast Guard, was optimized by modeling its errors with a stepwise regression. New models were also developed with the regression tree technique. The performance of the statistical models was better than 10 empirical models that are considered the most suitable to predict the maximal squat in the St. Lawrence Waterway. The models built by regression tree gave the best predictions.

This paper describes the stability of the west perimeter dike at the Craney Island Dredged Material Management Area (CIDMMA) using an undrained strength stability analysis. An undrained strength stability analysis expresses the undrained shear strength in terms of the effective overburden stress of the dredged material and the marine clay underlying the dike. An undrained strength stability analysis was used to evaluate the current stability of the west perimeter dike, the possibility of raising the perimeter dike, and the effect of undrained strength increase along with full consolidation by installing vertical strip drains on the current stability and the potential for raising the dike. Vertical strip drains would accelerate consolidation of the confined dredged material and underlying marine clay and thus produce an increase in undrained shear strength and dike stability. The analyses show that installation of vertical strip drains and full consolidation of the dredged material and underlying marine clay should allow the perimeter dike and dredged material to be raised and an increase in CIDMMA service life.

The present study is to parameterize the influence of regular progressive waves on the diffusion of a neutrally buoyant turbulent round jet experimentally. The jet, located at the middepth, discharges into the wave field horizontally in the direction against the wave propagation. The particle image velocimetry technique and the laser induced fluorescence technique were used to measure the velocity field and examine the jet cross-sectional profile. Three different wave periods with a range of wave amplitudes in each wave period were tested to investigate the effect of waves on jet diffusion. The wave conditions cover both the shallow water and deep water, whereas the wave slopes range from linear to weakly nonlinear. The results showed that the width of the jet was significantly affected by the waves. The wave dispersion enhanced the jet diffusion, especially for a larger wave slope and a shallower water depth. The results also showed that the wave-to-jet momentum ratio is the most important parameter to characterize the effect of waves to the diffusion of jet.

The Bosphorus Tube Tunnel beneath the Bosphorus Strait is under construction in Istanbul, Turkey, using the tunnel-element immersed method. It is well known that the Bosphorus Strait has a two-layer current system with a rapidly changing flow. To maintain quality and safety of tunnel-element installation, it is important to accurately forecast the current-flow condition for periods of $48\mathrm{h}$ to identify windows of opportunity for the element-immersion process. In this study, a forecast system is developed based on the information collected and analyzed over an immediate past five-day period $\left(120\mathrm{h}\right)$ to provide a two-day $\left(48\mathrm{h}\right)$ period current prediction required for the element-immersion process. The system consists of a water-level forecast model and a current forecast model. The water level is forecasted from air pressure and wind information obtained from on-line monitoring data and meteorological service forecasts. The current is then forecasted from the water-level data taking the two-layer density interface effect and the immediate preceding $120\text{-}\mathrm{h}$ current data (including its concurrent value) into consideration. This selected data-analysis period is determined based on our operational experience at the site. Both models are statistically constructed and calibrated using a year-long observation data set (October 2004–September 2005). It is found that the proposed forecast system gives sufficiently accurate current information for safe ongoing marine construction operation.

The present work is a numerical investigation on waves generated by a pressure disturbance moving at constant speed in a channel with a variable cross-channel depth profile. The channel profile, which is uniform in the along-channel direction, has a deep trench located along the centerline of the channel, and shallow banks near the channel walls. Characteristic features upstream and downstream of the moving pressure disturbance are related to the parameters of the pressure disturbance and the cross-channel profile. Our numerical investigation is based on the COULWAVE long wave model.