Journal of Waterway, Port, Coastal, and Ocean Engineering

Since the 1980s, the demand for Hong Kong’s container handling facilities has been increasing due to the robust economic growth in South China. As more and more vessels call on Hong Kong’s container terminals, the vessels moving in the basin surrounded by the container terminals will have a bigger chance of interfering with one another, due to the need to comply with navigation safety requirements. The interference often necessitates the vessels to stop occasionally while moving along their navigation paths in order to avoid potential collisions. This paper develops a simulation model for studying the impact of the vessel-traffic interference in Hong Kong’s terminal basin on its container terminals’ capacities. Major navigation safety requirements and terminal operational characteristics are considered in the model. The model’s simulation results show that the delays due to the vessel-traffic interference lead to a considerable reduction in Hong Kong container terminals’ capacities. This model can assist the container terminals in estimating the benefits of coordinating vessel movements in the terminal basin.

This paper describes the hydrodynamic characteristics of a pile-supported vertical wall breakwater, the upper part of which is a vertical wall, and the lower part consisting of an array of vertical piles. For regular waves, using the eigenfunction expansion method, a numerical model has been developed that can compute wave transmission, reflection, and run-up, and wave force acting on the breakwater. For irregular waves, the regular wave model is repeatedly used for each frequency component of the irregular wave spectrum. The wave period is determined according to the frequency of the component wave, while the root-mean-squared wave height is used for all the component waves to compute the energy dissipation between piles. To examine the validity of the developed models, large-scale laboratory experiments have been conducted for pile-supported vertical wall breakwaters with a constant spacing between piles but various drafts of the upper vertical wall. Comparisons between measurement and prediction show that the numerical model adequately reproduces most of the important features of the experimental results for both regular and irregular waves. The pile-supported vertical wall breakwater always gives smaller transmission and larger reflection than a curtain wall breakwater with the same draft as that of the upper wall, or a pile breakwater with the same porosity as that of the lower part, of the pile-supported vertical wall breakwater.

A buoy as an offshore structure is often placed over a convex such as a caisson or a submerged island. The hydrodynamic fluid/solid interaction becomes more complex due to the convex compared with that on the flat. Both the buoy and the convex are idealized as vertical cylinders. Linear potential theory is used to investigate the response amplitude and the hydrodynamic force for a buoy over a convex due to diffraction and radiation in water of finite depth. These are derived from the total velocity potential. A set of theoretical added mass, damping coefficient, and exciting force expressions have been proposed. Analytical results of the response amplitude and hydrodynamic force are given. Finally, the numerical results show that the effect of the convex on the response amplitude and hydrodynamic force for the buoy is ignored if the size of the convex is relatively smaller.

The scattering of linear water waves by an infinitely long rectangular structure parallel to a vertical wall in oblique seas is investigated. Analytical expressions for the diffracted potentials are derived using the method of separation of variables. The unknown coefficients in the expressions are determined through the application of the eigenfunction expansion matching method. The expressions for wave forces on the structure are given. The calculated results are compared with those obtained by the boundary element method. In addition, the influences of the wall, the angle of wave incidence, the width of the structure, and the distance between the structure and the wall on wave forces are discussed. The method presented here can be easily extended to the study of the diffraction of obliquely incident waves by multiple rectangular structures.

This paper presents a two-dimensional, well-balanced finite-volume model for runup of long waves under nonbreaking and breaking conditions. The model uses a conservative form of the nonlinear shallow-water equations with source terms and an explicit Godunov-type scheme along with the exact Riemann solver for the flux and moving waterline. A second-order scheme splits the two-dimensional problem into two sequential one-dimensional problems for time integration. The surface-gradient method leads to a well-balanced formulation of the flux and source terms and a piecewise linear interpolation reconstructs numerical data at cell interfaces to achieve second-order accuracy in space. This provides accurate descriptions of the conserved variables and small flow-depth perturbations near the moving waterline. The computed surface elevation, flow velocity, and runup show very good agreement with previous asymptotic and analytical solutions as well as laboratory data. The model accurately describes breaking waves as bores or hydraulic jumps and conserves volume across flow discontinuities.

Analytical solutions to a beach evolution equation are obtained for the case where the initial beach shape may be an arbitrary function of position and where the forcing conditions may be a (known) function of time. The focus of this paper is the derivation of a generalized solution to the one-line equation describing the impact that time varying forcing can have on beach development close to a groyne. Explicit solutions are obtained using an integral transform technique. The solutions are found in terms of closed-form integrals which, for all but the simplest cases, require numerical evaluation. Example applications of the new solutions are described.

An alternative graphical expression is presented for the computation of overfill ratio using the Dean method. The expression yields the same numeric results as the original Dean curves, but allows simple computation of the overfill ratio from a single curve for an unlimited range of sediment cases. The physical significance of results yielded from the Dean method is contrasted with those from the James-Krumbein method. A convenient numeric means to directly translate between phi and millimeter grain sizes is additionally noted.