Journal of Waterway, Port, Coastal, and Ocean Engineering

A comparison of three manual wave prediction models is carried out using 1972 waverider data from two deep‐water locations in Lake Ontario. The Sverdrup‐Munk‐Bretschneider model is compared with the JONSWAP model and with the relatively new model of Donelan. Only fetch‐limited, pseudo‐steady‐state events have been investigated. The accuracies in predicting the characteristic wave height and the period of the peak of the wave energy spectrum were found to be comparable for all three models. However, the accuracy of the Donelan model is slightly superior to that of the other two models; because the Donelan model can also predict the direction of the dominant wave energy on enclosed water bodies, where the fetch distribution is known, it could be useful for engineering applications in steady fetch‐limited conditions over deep water.

A design technique for inland navigation fairways is developed. In this method, three main phases are distinguished: economic studies, initial design phase, and final design phase. The last stage of the economic studies consists of the modal split. Qne of the results of the modal split is the volumes of commodities to be transported by inland navigation. These data are among many others required to cope with the initial design. During the initial design, all aspects involved are dealt with in a very general way: experience, non‐complicated models and “rules of thumb” play an important role. In the final design phase, the results obtained are refined using sophisticated mathematical models and small‐scale hydraulic models. Refinement studies may be carried out to study maneuvering, speed prediction, design of bank protections, and sedimentation. All studies are strongly interrelated, and a thorough coordination of the disciplines involved is essential. It is shown that the design technique has an iterative character in which cost‐benefit analysis and ranking matrices, or both play an important role.

Depth errors may occur in hydrographic surveys if tidal corrections are determined from water surface heights measured at points distant from the immediate vicinity of the soundings. Use of predicted rather than measured heights is another potential cause of error. Errors are presented for a hypothetical calculation of dredging pay quantities. Procedures for reducing errors are suggested, and methods of measuring tide height described.

For structures located in flood prone areas an engineering cost analysis method is developed to establish the least cost elevation of the structural floor. The least cost elevation is one yielding the lowest life cycle cost combination of flood damage costs, construction costs, operating and maintenance costs together with anticipated gradients, as well as appreciated replacement value costs. The method involves raising the design floor elevation until the incremental life cycle costs associated with the raise in floor elevation equals the decremental life cycle cost of the probable flood damage.

The factors affecting the economics of stacking and wheeled operations in container terminals are stated. By mathematical reasoning involving cost of land, cost of equipment and cost of labor, and their constituent factors inequalities were written and analyzed. From a small computer program which was written to calculate the relationship of the total cost of wheeled and that of stacking operations, graphs were developed for various values of top loader efficiency, number of days that containers stay in port, interest rates, and cost of land versus various values of the ratio between the total cost of stacking over the total cost of wheeled operations. In each graph, two areas were distinguished and separated by a horizontal line: the area above with values greater than one where wheeled operations are preferred and the area below with values of less than one where stacking operations are preferred. From studying these graphs, it is concluded that under the least efficient top loader operation (10 movements per day) the smallest interest rate and the smallest cost of land, six days of stay in port would be the longest time to justify wheeled operation.

The use of synoptic atlases of wave climatologies for determining shore line evolution is examined critically. It is concluded that the fineness of discretization of wave height is not too important, as long as energy is conserved, but a fine discretization of wave angle is needed. Due to importance of order of sequential wave events or time history of the wave input, a Monte Carlo simulation of the wave climatology is proposed to determine shore line location probabilistically instead of deterministically.

A six‐year program, with a budget of $6 million, was undertaken by the Office of Sea Grant in 1976 to develop improved engineering predictive models for transport of sediment in and near the surf zone by waves and currents. The project, called the Nearshore Sediment Transport Study, has involved ten investigators from six different institutions who worked cooperatively on field studies. Three major field experiments have been conducted, the first in 1978, the second in 1980, and the last in 1981. The first two field experiments had a duration of approximately a month and involved synoptic measurements of more than 100 parameters of surf zone dynamics and sediment response. Sand tracer experiments were also performed and the last two field sites include concurrent trap experiments for longshore transport. All data were recorded on magnetic tape and more than a billion words were obtained in the second experiment. In the final two years of the project, emphasis has been placed on the formulation of predictive models and their verification using the NSTS data sets.

A previously developed thermodynamic model for ice formation, growth, and dissipation has been extended to account for ice transport and deformation due to wind and water stresses. This ice dynamics simulation model has been developed for application to the Great Lakes to aid in forecasting ice conditions during winter navigation. The method of approach utilizes the macroscopic continuum hypothesis for the fragmented ice field. The external driving force includes the time‐dependent wind and water current fields. The internal ice resistance is represented by a viscous‐type constitutive law employing both shear and bulk ice viscosities. Several alternative empirical or semi‐empirical expressions are considered for representing the internal ice pressure. The model has been applied to Lake Erie under varying wind conditions. Model output reproduces the characteristic features of ice field movement and deformation. Calibration of the model is now underway using observed data from specific Lake Erie ice transport events.

A two‐dimensional (in a vertical plane) branching model is developed to simulate salinity distribution in complex estuaries. The model is applied to a one‐month salinity study in the Chesapeake Bay during a period of low freshwater discharges from the Susquehanna River. Model results compare well with observations in the prediction of depth‐averaged salinities as well as vertical salinity profiles. Simulation of a hypothetical flow reduction suggests significant salinity increase near the head of the bay, and a stronger bottom salt intrusion over the entire bay.

An approximate method is presented for estimating wind-wave growth over flooded areas where there is a major effect from bottom friction because of dense vegetation. The method estimates wave growth using an adjusted fetch length which is shorter than the actual fetch length. The adjusted fetch length is determined by comparing decay factors for the case of low bottom friction and the case of high bottom friction.

Diffraction of linear, monochromatic surface gravity waves by circular cylinders is reviewed by constructing an axisymmetric Green's function by an eigenfunction expansion. This study indicates that the Green's function method is capable of solving a complex problem, such as nonlinear diffraction theory. Nonlinear diffraction theory or second-order velocity potential can then be used to solve the practical problems faced by designers when utilizing large diameter cylindrical shapes for offshore structures in large amplitude storm waves.

The diffraction of a solitary wave around a vertical surface-piercing circular cylinder is described to a first approximation, and the resulting forces on the cylinder are calculated. This represents a limiting case of a cnoidal wave diffraction solution given previously, and in order to treat this limit the incident wave is represented in terms of a Fourier integral rather than a Fourier series. The maximum force coefficient and the dimensionless runup depend on a single parameter which replaces the usual diffraction parameter. A criterion for diffraction to be significant for shallow water waves is established and depends upon both the diffraction parameter as well as the additional parmater used here.

Prediction of the total force on a vertical cylinder in waves has been investigated. Drag and inertia coefficients on a small section of span have been measured for a range of orbital shapes. There is considerable scatter but rms in-line force is in reasonable agreement with U-tube data unless orbital shape approaches circular when local and total force is markedly overestimated on a quasi-2-D basis. For surface Kc less than about 12 lift is predominantly at twice the wave frequency. A quasi-2-D calculation using U-tube data underestimates total force for deep-water waves and in general lift prediction is somewhat unreliable.

A device for the calibration of a hot film probe subjected to a simple harmonic motion is described. It works on the basis of constant amplitude and variable periods. Results of calibration with such periodically varying velocities indicate its suitability for dynamic calibration especially for measurements in wave fields.