Journal of Waterway, Port, Coastal, and Ocean Engineering

Simulation is a very powerful tool for the analysis and planning of seaport operations. A well-designed and calibrated simulation model can provide useful insights about complex port operations that analytical models cannot capture accurately. An important part of any port operations simulator is the module that produces the ship traffic. This paper presents a ship traffic modeling methodology based on statistical analysis of containership traffic and cargo data obtained from a port in the United States. Implementation of the described procedure led to the creation of a simulation algorithm that captured ship traffic characteristics well. Functional relationships are also developed between ship length and ship draft and between ship length and cargo capacity. The relationship between the average number of handled containers and the number of cranes used is described. The information and conclusions provided here are intended to give guidance on achieving time efficiency and accuracy in the modeling of ship traffic and calibration of container port simulation models.

To increase the understanding of complex flows in dredging cutter heads, an experimental and numerical investigation of these flows has been made. As a first step toward the investigation of the mixture flow in a complete cutter head that actually cuts the soil, the simplified case of the flow of water in a freely rotating cutter head is considered here. Using stationary acoustic doppler velocimetry, three-dimensional velocity fields inside a cutter head have been measured. In addition, finite-element computations of the velocity field have been performed, using the potential flow model. These experimental and numerical investigations clarify the role of the angular velocity of the cutter head and the suction flow rate in the suction pipe that is generated by the dredge pump. Depending on a nondimensional flow number, three flow regimes are observed in the computations. For low flow numbers, the rotation of the cutter head dominates the flow, and an outward flow occurs near the cutter ring. For high flow numbers, the suction flow dominates the flow, and an inward flow exists around the entire contour of the cutter head. For the flow number corresponding to the theoretical hydraulic design condition, there is a balance between the flows induced by rotation and suction. The measured and computed velocity fields have been compared, showing good qualitative agreement and reasonable quantitative agreement.

An investigation into the peak velocities in internal solitary waves characteristic of those found on the ocean thermocline is described. Measurements made using particle image velocimetry in a laboratory tank are compared to the predictions of Korteweg-de Vries (KdV) theory, in both two-layer and continuously stratified forms, and to a two-layer fully nonlinear theory. The dataset comprised 60 waves, covering amplitudes in the range of $0.16⩽a/h_1⩽0.67\text{,}$ layer depths in the range of $0.125⩽h_1/h_2⩽0.5\text{,}$ and density differences of 2.5 and 7.5%. It is found that KdV theory predicts peak velocities well when the ratio of wave height to upper layer depth is less than 0.4, while the fully nonlinear theory performs better for higher ratios.

A synthesis of existing models and formulas is made to compute the virtual performance of rubble mound structures in shallow water under combined storm surge and breaking waves for sequences of hurricanes. The computed results for ten 500-year simulations are presented for a typical structure as an example. The crest height and armor weight of the structure are designed against the peak of a 100-year storm. The structure designed conventionally is exposed to approximately 350 storms for each 500-year simulation. The computed wave overtopping rate and volume during the entire duration of each storm are analyzed to assess the severity of flooding hazards. The computed progression of damage to the armor layer is caused episodically by several major storms but slows down as the structure ages. The computed results are also used to quantify the equivalent duration of the peak of a storm that yields the same overtopping water volume and damage increment as those computed for the entire storm duration.

A model to estimate volume loss of armor stones caused by abrasion under wave conditions occurring during a structure’s lifetime is proposed. It accounts only for abrasion caused by stone movements, neglecting the effects of stone breakage, wetting-drying, freezing-thawing cycles, and chemical attack and is based on the assumption of proportionality between abraded volume and abrasion work. The model represents rock resistance to abrasion and to unit size and makes use of empirical relationships providing the average frequency of movement and displacement length of armor units. Wave loading is described with a probabilistic analysis. The present model is discussed in the light of a previous one. The comparison makes possible the estimation of the influence of external agents, other than stone mobility and size, on volume loss.

The equations of motion of a spring-mass system are used to describe a vessel’s mooring system. These equations employ added mass and hydrodynamic damping coefficients, which depend on vessel shape and the proximity of free-surface and solid boundaries. The present study has experimentally determined these coefficients for barge tows moored in the chamber of navigation locks. Seven lock chamber configurations were tested in which the width, depth, and length of the chamber and the beam width and length of the tow were varied. Values of the added mass coefficient and a nondimensional form of the damping coefficient are presented. Subsequent to modeling flow in a lock chamber, these coefficients can be used in conjunction with hawser properties (spring constants) to estimate hawser forces generated during locking operations.