Journal of Waterway, Port, Coastal, and Ocean Engineering

A Green's function approach is utilized to calculate the dynamic response of a long, submerged, cylindrical shell structure subjected to horizontal or vertical ground excitation. The problem is idealized as two‐dimensional, and the governing equations are taken to be those of a circular arch. The arch is assumed to be clamped and to vibrate in its own plane; both flexural and extensional effects are included in the formulation. The fluid is assumed to be linearly compressible and to undergo small‐amplitude irrotational motion. A new Green's function is presented for the fluid domain based on an eigenfunction expansion technique and is used in conjunction with a previously derived Green's function for the arch to solve the coupled fluid‐structure interaction problem. Numerical examples are presented that illustrate the influence of the direction and frequency of ground excitation and the various geometric and material properties on the hydrodynamic pressure distribution on the arch and its associated dynamic response.

A simple explicit numerical model suitable for a personal computer is discussed that provides for the refraction and shoaling of linear and nonlinear water waves over irregular bathymetry, including wave‐current interaction. Finite‐differenced forms of the conservation of wave action and the irrotationality of the wave number equations are used in the model. Applications of the model to a planar shoreline, where Snell's law is valid, show that the model results are independent of the step size. Two other bathymetries are examined: one, an idealized coastline with a rip channel; and the other, a section of the New Jersey coastline. The model output is displayed in terms of wave height and direction vectors.

A solution, exact to the second‐order in wave steepness, is presented for the hydrodynamic loading on a stationary, truncated circular cylinder in water of arbitrary uniform depth. Two situations are considered: the structure may either be completely submerged and resting on the seabed, or partially immersed in the free surface. The method employed to calculate the second‐order forces and moments due to the second‐order velocity potential does not involve the explicit calculation of this potential. Instead, the hydrodynamic loading components due to this potential are found by applying Green's second identity and solving a series of linear radiation problems at the second‐order wave frequency. Numerical results are presented for several example structures that illustrate the relative importance of the second‐order effects over a range of wave periods. In general, the components that are explicitly due to the second‐order potential are found to result in the dominant loading effects at that order.

This paper reports a numerical modeling study of tidal transport in the Arabian Gulf. Due to the large surface area and relative shallowness of the Gulf and the limiting computing resources, a two‐dimensional depth‐averaged model and a coarse spatial resolution of 19.05 km was used in the study. The model calculated tide ranges, and phases of low and high tides compared favorably with tide table data. To provide further insight into transport in the Gulf, an Eulerian‐Lagrangian Advection Dispersion (ELAD) model was developed and applied. Using velocity and depth information calculated from the hydrodynamics model, the ELAD model was used to characterize transport in the Gulf through a number of simulated tracer release scenarios. The study results reveal complex circulation patterns within the Gulf and suggest a slow exchange rate between the waters of the Arabian Gulf and the Gulf of Oman. Refined spatial resolution by the model, and increased field observations are recommended for a more detailed calculation of tidal transport in the Gulf.

Wave‐induced forces on a submarine pipeline in regular waves placed near a plane boundary were studied in the inertia‐drag regime. The in‐line root mean square (rms) coefficient was computed using Morison equation and linear wave theory. A Fourier analysis was carried out on transverse forces and nth harmonic transverse rms coefficients were evaluated. Both these rms hydrodynamic coefficients were correlated with Keulegan‐Carpenter number or period parameter, gap ratio, and depth parameter. The rms hydrodynamic coefficients were found to depend not only on period parameter and gap ratio but also on depth parameter. The dependence of the hydrodynamic coefficients on depth parameter is such that they decrease with a decrease in depth parameter. The presentation of the results as a single force coefficient, such as rms coefficients, is found to reduce the scatter in the results considerably and avoids any phase problems. It is found from the Fourier analysis that the transverse force oscillates at twice the oscillation frequency of the wave at large values of period parameter, at least within the range of period parameter encountered in this investigation.

The changes in flow field around an ice mass drifting in a current near a large offshore structure are investigated using potential theory. A formulation in two dimensions is adopted here to allow relatively accurate results to be obtained for very small separation distances, and an approximate method to extend the results to threedimensional applications is described. The motions of the ice mass and current interactions are represented by five unit potentials and the hydrodynamic forces are obtained by the Bernoulli equation. The proximity effects are then generalized by introducing a set of hydrodynamic coefficients for the ice mass, which are expressed in terms of geometry of the structure and ice mass. A numerical model based on the boundary integral method is developed to solve the problem. A set of coefficients for the special case of two circular cylinders is presented in this paper. The strengths and weaknesses of the proposed model, as well as its practical applications, are discussed.

This paper describes the analysis and experimental work leading to the development of design criteria for an outlet structure. The recommended design consists of a transition and stilling basin with straight diverging sidewalls. The rate of sidewall divergence is expressed as a function of the width ratio and Froude number. Design values were determined from model tests carried out for both round and square conduits. Design criteria were based upon observations on the effective position of the hydraulic grade line at the outlet, head losses in the transition, depth and velocity distribution in the transition, stability of the hydraulic jump, downstream velocity distribution and scour tendencies in the discharge channel. A major portion of the paper is devoted to details of the recommended design procedure, including the rationale behind the various recommendations. An example is worked to illustrate the procedure, and the performance data for one of the test models is included.

A method of obtaining mineral deposits through the electrolysis of seawater was examined for potential use as an agent for the structural enhancement of existing marine structures, and as a process for the preparation of a primary marine construction material. An electrolytic cell was established between graphite anodes and cathodic test specimens submerged in seawater using an external power supply. After several months of electrodeposition calcareous mineral deposits were obtained on both wood and wire-mesh test specimen using this electrolytic process. Structural testing of the wire-mesh specimens indicated that the mineral deposits increased the strength of the specimens to a limited degree. The long time period required for significant mineral deposition and the typically nonuniform distribution of deposited minerals on the cathodic specimens were found to be the most constraining factors of the electrodeposition process. However, because of the low power requirements of the process, its applicatiion in some instances could be justified.

Runup is one of the most important factors affecting the design of revetments exposed to wave action. Generally, riprap revetments are designed so that little or no runup exceeds the top of the protection. In the past this has been a difficult prediction to make, but now a new method for calculating the approximate upper limit of wave runup on riprap has been formulated. This method is based on laboratory data and is easy to apply through use of a recommended or an alternative formula. The recommended formula uses the Airy wavelength, $L_P$, while the alternative formula uses the more standard deep-water wavelength, $L_o$. The alternative formula provides an easy way to calculate a good ``rule-of-thumb'' estimate for runup. Both formulas can be used to compute the elevation to which protection needs to be extended to prevent exceedance by runup, or used to estimate potential severity of wave overtopping.