Journal of Waterway, Port, Coastal, and Ocean Engineering

Alongshore gradients in wave energy and propagation direction were observed near a pier that extends 500 m from the Duck, N.C., shoreline to about 6-m water depth. When incident waves approached the beach obliquely, wave energy observed near the shoreline 200 m downwave of the pier was as much as 50% lower than observed 400 m downwave, and waves close to the pier were more normally incident than those farther downwave. Alongshore gradients were much smaller 400 m offshore of the shoreline, upwave of the pier, and with nearly normally incident waves, confirming that the gradients are associated with wave propagation under the pier. A spectral refraction model for waves propagating over the measured bathymetry, which includes a depression under the pier, accurately predicts the observations 400 m downwave of the pier, but overpredicts energy near the pier. Refraction model predictions that include partial absorption of wave energy by the pier pilings reproduce the observed alongshore gradients, suggesting that piling-induced dissipation may be important.

The influence of wave reflection and energy dissipation by breaking and by porous flow induced by a permeable submerged structure on second-order mean quantities such as mass flux, energy flux, radiation stress, and mean water level is analyzed. For this purpose, analytical expressions for those mean quantities in terms of the shape functions are obtained. The dependence of those quantities on the incident wave characteristics, structure geometry, and permeable material characteristics is modeled, extending the writers' previous work including wave breaking. Two models for regular waves are presented: a 2D model to be applied to submerged trapezoidal breakwaters and a 3D model for submerged permeable rectangular breakwaters. Both models are able to reproduce experimental wave height transformation as well as mean water level variations along the wave flume with reasonable accuracy. Results give useful information for engineering applications of wave height evolution and set-up and set-down evolution in the vicinity of the submerged permeable structure.

A three-dimensional numerical model based on the complete Navier-Stokes equations is developed and presented in this paper. The model can be used for the problem of propagation of fully nonlinear water waves. The Navier-Stokes equations are first transformed from an irregular calculation domain to a regular one using sigma coordinates. The projection method is used to separate advection and diffusion terms from the pressure terms in Navier-Stokes equations. MacCormack's explicit scheme is used for the advection and diffusion terms, and it has second-order accuracy in both space and time. The pressure variable is further separated into hydrostatic and hydrodynamic pressures so that the computer rounding errors can be largely avoided. The resulting hydrodynamic pressure equation is solved by a multigrid method. A staggered mesh and central spatial finite-difference scheme are used. The model is tested against the experimental data of Luth et al., and the comparison shows that higher harmonics can be modeled well. Comparison of the model solutions with the elliptic shoal case confirms that the present model works well for wave refraction and diffraction with strong wave focusing.

An experimental study of runup on slender columns in steep, deep water waves is described. The depth, steepness, and scattering regimes were chosen to be representative of semisubmersibles in storm waves. Runup predictions from several theories were compared with the data; the theories were linear diffraction, a superposition method, velocity stagnation head, and a related semiempirical method. It was found that all underpredicted the runup extent by significant margins, up to a factor of two, with the exception of the semiempirical method, which provided a conservative design curve for the shorter periods.

This study deals with the runup of solitary waves on a uniform plane beach connected to an open ocean of constant depth. The waves are nonbreaking during the runup process. A nonlinear solution to the classical shallow water equation, that describes the wave characteristics on the beach, is obtained analytically by using a hodograph transformation. It was found that the nonlinear theory agreed well with experimental results. The maximum runup predicted by the nonlinear theory is larger than that predicted earlier and the correction is on the order of the offshore relative wave height for a given slope. This correction for nonbreaking waves on beaches decreases as the beach slope steepens.

Investment planning for systems with interdependent queues, such as a series of interacting waterway locks, is a very challenging problem. Under budget constraints, it must be determined which projects should be selected and when they should be funded to minimize the present value of total cost over the planning horizon. Due to interdependence among service stations (e.g., locks), investment planning for such systems cannot be analyzed separately for each station. Published models on investment planning for interdependent projects are rare and difficult to apply to a series of queuing systems. A genetic algorithm approach is presented in this paper for solving project sequencing and scheduling problems for such systems. A numerical example is designed to investigate the proposed algorithm. Results indicate that the proposed approach is quite efficient in finding very good solutions.