Journal of Waterway, Port, Coastal, and Ocean Engineering

In comparison with wave modeling on an open coast, the complex geometry and bathymetry of estuaries, the unsteady conditions associated with estuarine circulation generated by tides and winds, and the relatively inadequate field data present a unique challenge. This study utilizes an unsteady, curvilinear spectral wave model that has the flexibility to resolve large geometric and bathymetric gradients and allows for consideration of unsteady forcing and currents to predict wind waves in Mobile Bay, Alabama. First, a laboratory data set on wave transformation over a circular shoal is chosen to test the curvilinear wave model. Excellent agreement is found between the numerical results and the laboratory measurements with a directional wave input and fine spatial resolution. Second, a three-dimensional circulation model is used to predict the varying current field and water levels that serve as the input to the wave model. The predictions of the wave model under unsteady forcing and ambient currents are then compared with the existing field measurement of wind waves in Mobile Bay. Numerical experiments are carried out to examine the effects of estuarine circulation and grid resolution on the model result. The study shows that the technique of linking a spectral wave model to a hydrodynamic model on curvilinear grids is an effective tool for wave prediction in estuaries.

This paper evaluates the performance of two numerical wave models, GHOST and STWAVE, with measurements made in an idealized inlet physical model. The emphasis of this paper is on the overall performance of these models in coastal inlets. Both wave models are similar in that they employ a finite-difference method to solve the wave action conservation equation for the steady-state wave spectral transformation. However, these models differ in the computation of diffraction, reflection, wave breaking, and representation of the directional spectrum transformation. The models’ performance is compared with a new set of physical model data for four different idealized inlet configurations. Wave height is measured in the physical model by a linear array of capacitance wave gauges, and wave direction is measured by a remote-sensing video-camera system. The comparison with data is presented as mean absolute relative errors of wave height and mean absolute difference of wave direction. Both wave models produced similar results, but neither could accurately describe waves observed in the physical model in inlets and near structures. The mean absolute relative error of wave height prediction from models was between 22 and 40% as compared with the measured data. The mean absolute error of wave direction estimates ranged from $5\text{to}12\text{degrees}$ . Overall, wave direction estimates from GHOST in inlets and near structures compared slightly better with measurements.

A three-dimensional numerical solution was developed to determine the wave field in a narrow channel with side porous caves. The solution was achieved by applying the boundary element method. The model was applied to determine the effect of the geometry of caves and the physical and hydraulic properties of the porous material in the caves on the wave field in the channel. The results show that the cave geometry and the physical and hydraulic properties of porous material in the cave have a significant effect on the wave field in a channel. Wave transmission down the channel usually decreases with increasing cave length and cave width and decreases with increasing porosity. Moreover, wave transmission usually decreases with increasing wave-damping properties for porous material of low damping properties and increases with increasing wave-damping properties for porous material of high damping properties. A reduction of wave transmission down the channel, often substantial, can usually be achieved by increasing the porosity and increasing the wave-damping properties of the porous material. The results and additional analysis show that a reasonable wave transmission level can be achieved even for fairly short porous caves and that the model can be applied to select an optimal cave system for any prespecified conditions. Theoretical results are found to be in reasonable agreement with experimental data.

The main objective of a project is to verify the requirements and target levels for values of reliability, functionality, and operationality during the useful life of the structure. Such requirements should be provided by external studies carried out by the promoter. In their absence, the engineer has to specify requirements using his or her own criteria. This paper describes a procedure that defines the target levels for maritime structures in terms of their general and operational intrinsic natures. These natures are used to evaluate the importance of the structure as a function of the economic, social, and environmental impact produced in case of serious damage or a total loss of functionality and stoppage, respectively. This procedure gives recommendations for values of a structure’s minimum useful life, joint probability of failure against the principal failure modes, adscribed to ultimate and serviceability limit states, minimum operationality, average number of admissible technical breakdowns, and maximum allowed duration of a stoppage mode.

A mathematical model capable of simulating tropical cyclone tracks and central pressure histories over the Coral Sea, Australia, is described. The modeling approach assumes that each cyclone is an independent realization of the same underlying stochastic process. Relatively simple autoregressive models are used for the time series of latitude, longitude, and central pressure. The model is used to generate a large database of synthetic storms whose statistical characteristics are shown to simulate those of the population of real storms. Each synthetic storm can be used, in conjunction with a separately developed wind field model, to drive numerical models for computing wave heights and water levels (including storm surges) throughout the Great Barrier Reef Marine Park. In this way, the sample size available for estimating extreme wave heights and water levels is greatly increased