This semi-relieved shipbuilding drydock with tied back steel pile walls has recently been completed on San Diego Bay. Pressure relief is accomplished by cutoff walls and an underdrain system with continuous pumping. Substrata pressure is monitored by piezometers set in deep pipes with remote reading dials at the surface. The underdrain system is separate from the main dock dewatering system. The gate is floated by dewatering flotation chambers with compressed air.
The test is conducted at low values of Reynolds number (<3 × 104). The measured data are analyzed to calculate the hydrodynamic coefficients in the form of inertia, drag, and lift coefficients. The values obtained from the 1-ft (0.305-m) sections are used to correlate the measured force data on the entire tube. The coefficients are found to correlate well with the period parameter which follows Froude scale. Resultant forces are found to be as much as 60% higher than the in-line force. The lift coefficients are calculated up to the fifth harmonic and are represented as functions of period parameter. The frequencies of the lift force are found to have a definite trend with the number of eddies formed depending on the period parameter. Dependence on the period parameter makes scaling to other (e.g.,prototype) sizes relatively straightforward, except for the uncertainty of flow effects from the subcritical (e.g., in the test) to the supercritical (e.g., in the prototype) Reynolds number range.
A time-dependent numerical model, which treats fully evolved wind-driven canopy flow as a coupled two-layer system, is developed. The interfacial stress is formulated in terms of a coupling coefficient and the flow differential. The resistance afforded by a vegetative canopy is parameterized in terms of a drag coefficient and dimensional properties of the canopy elements. With flow confined strictly to the canopy, the calming effect of the canopy is introduced through a sheltering coefficient. The canopy is modeled as a set of rigid uniform structures orientated normal to the flow and evenly distributed with specified density over the bottom. The algorithm is tested by simulating the steady-state water-surface profiles observed in a laboratory channel containing wire screen obstructions. The model is applied next to a wind-driven rectangular basin with simulated vegetation specified over half the bottom.
A computational system is presented for the calculation of long waves in harbors and coastal seas. The numerical method used is a three level implicite finite difference scheme, using the fractional steps technique. Tests on harbors under gale conditions with waves of one minute period, show that nonlinear instabilities develop, but they can be dissipated by iterating for equation coefficients.
Limitations on ability of numerical models to model flow and dispersion of pollutants in coastal areas due to fundamental limitations in knowledge of exchange coefficients are covered. Specific limitations result from effects of stratification on control of flow and mixing rates, and from lack of understanding of the transverse exchange process. Examples of specific computer models are given, with emphasis on why some models give reliable results despite the limitations previously mentioned.
Turbulent eddies of different sizes control the far field of pollutants discharged to the marine environment. For the fine turbulence and regular advection, the validity of the local isotropy law is considered, and it is shown how the shore, circulation cells, multiple energy inputs, velocity gradients, waves, and other factors modify this law in the coastal zone. A model of the dispersive effects due to wave-current interactions is proposed and a formula is given for the spectral eddy diffusivity due to waves and currents. A solution of the steady-state diffusion equation has been derived for a fairly general case of exponential velocities and eddy diffusivities. By the Fourier transform, this solution has been used to embody the effect of mesoscale eddies, which destroy the aforementioned regular spreading patterns. Among other tools, a step-by-step procedure is proposed as a combination of fine turbulence and mesoscale effects.
Economy in the design of maritime jetties has led to the investigation of structural forms using frames of steel box girders. However, due to their greater flexibility and lower structural damping capacity they are prone to vibration hazards. A general analytical procedure for studying this phenomenon is given and has been checked by a series of experiments on a model. The sources of disturbance that a jetty will be subjected to are either transient or steady. The first covers cases of impact due to cargo handling or suddenly applied bollard forces, while the second category is concerned with periodic forces, e.g. rotating machinery, vortex shedding, or wave forces. For the first category methods of determining peak stresses and displacements are given while for the second category it is shown that under certain conditions resonant states can occur that could render the jetty unserviceable.
Upon addition of sediment/seawater mixture to the seawater column, most trace metals were found to display a pattern of immediate release. These released metals were subsequently removed. The removal is gradually under reducing environments and almost immediately under oxidizing environments. The degree of release was significant for Fe, Mn, and Ni. The Cr, Cu, Pb, and Zn were moderately released. The release of Ag, Cd, and Hg was negligible. After resedimentation, the migration of trace metals between the sediment/seawater interface were found to be influenced by the redox conditions of the overlying water. In general, three patterns of metal behavior were observed: (1)The release amount increases as the redox conditions become more reducing (Fe and Mn); (2)the release amount increases as the environment becomes more oxidizing (Cd, Cu, Ni, Pb, and Zn); and (3)no significant release (Cr and Hg). The soluble metal concentrations during and after open water disposal of dredged materials were found to be in the range of sub-ppb to ppb with the exception of Fe, under reducing condition.
A two-dimensional finite element analysis of the thermal state of man-made frozen islands is presented. The model includes an air-ground interface energy exchange simulator that incorporates available meteorological parameters for application to offshore areas in the Alaskan arctic. Comparison of simulations with analytical and available data indicates an accurate and efficient model. Two hypothetical island configurations are analyzed using actual meteorological data obtained at Barter Island, Alaska. Results suggest that islands constructed of dredged materials are feasible in shallow waters.
Results of previously pubished theoretical studies suggest that properly designed inlets and channel constrictions, or both, can considerably increase the mean current in coastal channels. This was further investigated by laboratory experiments in a channel of uniform width and depth at each end connected to the same tidal basin. A mean current was induced by providing one end of the channel with a constriction in the form of a submerged weir. Measured values for the mean current were in good agreement with values obtained by numerical integration of the governing hydrodynamic equations. For each experiment the direction of the mean current was the same for each point in the vertical. The direction of the mean current was not the same for all experiments. To aid in the interpretation of the results an approximate analytic expression for the mean current was derived.
Patterns of beach erosion and accretion due to jetty construction are examined for the Oregon coast which has a seasonally reversing littoral drift with a zero or near zero net drift. Thus the shoreline changes do not result from the jetties blocking a net drift. Shoreline accretion took place adjacent to the jetties, both north and south, filling the embayments formed between the jetties and the prejetty shoreline. The amount of accretion depended on the size of the embayment created. Sand for this accretion was supplied by beach erosion at greater distances from the jetties. In the case of the jetties at Tillamook Bay, the erosion was sufficiently severe to breach Bayocean Spit. A computer model is developed to simulate shoreline changes that occurred following construction of the Siuslaw River jetties. The model demonstrates deposition next to the jetty and erosion at greater distances, showing good agreement with the actual shoreline changes.
The basic principles of the engineering approach to similitude is given with emphasis on coastal engineering applications. In contrast to the parallel that exists between the Froude similitude and the Reynolds similitude as it is often formerly presented, the parallel between the similitude of short model and similitude of long model is stressed as the most practical engineering approach to scale model technology. Scale effects are determined quantitatively as the results of viscous damping and capillary effects. Density effects are examined, and the problem of similitude of wave forces—or more generally of time-dependent phenomenons—are quantitatively determined. Some digressions on movable bed scale models are also presented.
The spatial periodic function is considered in the investigation of the water waves interaction with the row of evenly spaced vertical cylinders under the assumption that the incident of wave direction is arbitrary. The effect of the presence of neighboring cylinders on the wave force on a given cylinder is derived and the equivalent mass coefficients are calculated. The theory is compared with past experimental results on the inertia-predominant wave force and the transmission coefficient through the barrier.
