The finite-element model for modified Boussinesq equations developed in Part I of this paper is used to study harbor resonance problems. The internal wavemaker technique is implemented on an unstructured finite-element mesh, and a sponge layer is used as an open boundary condition. Both linear and nonlinear harbor oscillations in rectangular and circular basins are examined, and experimental measurements and analytical solutions are used to validate the model. Finally, the wavelet transform is employed to analyze transient features of the nonlinear resonance problem.

Finite-Element Model for Modified Boussinesq Equations. II: Applications to Nonlinear Harbor Oscillations

Influence of offshore topography on infragravity period oscillations in Two Rocks Marina, Western Australia

The numerical wave model HARBD has been used extensively within and outside the U.S. Army Corps of Engineers for estimating waves in harbors. The model was originally developed for long waves (harbor oscillations). It has been extended for use with short waves (wind waves and swell) and validated by several investigations, most notably Chen's (1986) fundamental investigation of long waves in a rectangular harbor. This study focuses on short-wave validation. The model is tested with several simple domains, in most cases with uniform depth. It is validated with laboratory data for irregular wave diffraction around a semi-infinite breakwater. Both broad and narrow directional spreads are considered. The model is also compared to widely accepted curves for regular and irregular wave diffraction through a breakwater gap. Field validation of the model for Kaumalapau Harbor, Lanai, Hawaii, is discussed. Tests demonstrate the effect of input parameters on model results and provide guidelines about the choice of p...

Validation of Numerical Model for Wind Waves and Swell in Harbors

Publisher Summary This chapter provides a review of some state-of-the-art nearshore wave models that can be used for practical prediction in engineering studies. The chapter describes modeling philosophy, strengths, and limitations of models based on the steady state energy equation and the steady and unsteady state mass and momentum equations. Coastal engineering projects such as those dealing with wave agitation in harbors, beach protection, maintenance of navigational channels, studies of shoreline evolution, etc. typically require a detailed knowledge of the wave field in the project area. Mathematical models of wave propagation attempt to simulate the various mechanisms that induce the transformation of waves. This chapter reviews some wave models that strive to provide an acceptable mix of simplification, sophistication, and convenience of application from the standpoint of practical engineering. The purpose of this chapter is to briefly describe the overall philosophy, methodology, advantages, difficulties, and some applications of each modeling strategy. The chapter describes two kinds of wave models commonly used for coastal engineering applications: models based on the conservation of energy and models based on the conservation of mass and momentum. Both types of models can, by some rigorous or approximate method, incorporate many of the mechanisms mentioned in this chapter. Concluding remarks address some general difficulties that a practicing engineer is likely to encounter while using numerical wave models.

Wave Prediction Models For Coastal Engineering Application

Two-dimensional elliptic water-wave models based on the mild-slope equation find wide application in engineering and other studies. Model results are often adversely influenced by approximate treatment of the open boundary condition. A method to incorporate the exact radiation condition at infinity in finite-difference models is therefore developed. Since directly matching the solutions within the computational domain to those outside is too stringent a requirement, the new method is based on minimizing the overall discrepancy between the solutions along the open boundary. This relaxation permits the development of a suitable solution method, which is tested against analytical solutions for two situations. Satisfactory results are obtained with no artificial reflection of wave energy from the open boundary, even when it is placed very close to the scatterer.

Outgoing boundary conditions for finite-difference elliptic water-wave models

: The state of Hawaii identified the need for Barbers Point Harbor to accommodate larger ships and increase the number of available berths. Modifications to the harbor were proposed, including widening the entrance channel, and deepening (from 38 to 45 ft) and expanding the harbor basin (1,000-ft by 1,100-ft area on the northeast side of the harbor). Physical and numerical (computer) model studies were conducted from September 1990 to June 1992 at the U.S. Army Engineer Waterways Experiment Station to evaluate the technical feasibility and optimize the design of the proposed modifications. In addition to physical and computer model studies, navigation studies were also conducted using a scale model C9 container ship in the physical model. Recommended modifications to Barbers Point Harbor include flaring of the outer 1,000 ft of the entrance channel from 450 ft wide to 750 ft wide, deepening the channel to 49 ft, constructing a 450-ft jetty along the north side of the entrance channel, deepening the harbor to 45 ft, and dredging a 1,100-ft by 1 ,100-ft expansion area in the harbor basin.

Physical and Numerical Model Studies of Barbers Point Harbor, Oahu, Hawaii

: This report summarizes the field monitoring program and physical and numerical model studies that have been conducted to date for Barbers Point Harbor, Oahu, HI This harbor was selected for study as part of the Monitoring Completed Coastal Projects (MCCP) Program in FY 85 The report describes the following: (a) previous physical and numerical model studies conducted in the planning stages of the harbor, (b) state-of-the-art physical and numerical model studies used to estimate harbor response in the existing harbor complex, (c) a field monitoring program for collecting wind wave and long-period waves outside and inside the harbor, (d) intercomparison among previous and current model studies and field data relative to harbor response and deepwater and nearshore coupling between intragravity and wind waves, and (e) evaluation of the effectiveness of the existing rubble-mound wave absorber in dissipating wave energy inside the harbor Conclusions and recommendations are presented and an extensive appendix containing monitoring program results is provided Barbers Point Harbor, Numerical models, Harbor modeling, Physical models, Harbor monitoring Prototype measurement

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Barbers Point Harbor, Oahu, Hawaii monitoring study

: The US Army Engineer Waterways Experiment Station 's Coastal Engineering Research Center was requested to provide technical assistance in engineering analysis and evaluation of two proposed channel enlargement plans for Morro bay, California. These plans were developed to alleviate the hazardous conditions present at the entrance. This report details the study and provides final results to CESPL. Significantly wave heights, periods, and directions taken from the Wave Information Studies' (WIS) hindcast data base were input into the Regional Coastal Processes Wave finite difference model and transformed to breaking conditions along Estero Bay. Southern swell data were taken from an offshore directional buoy moored near Los Angeles, California, during 1984-85 and similarly transformed. The resulting breaking wave heights, periods, and directions were used to calculate longshore flux factors for use in sediment transport computations. The final results of the study indicated that the frequency of wave breaking would decrease at the entrance after either improvement was implemented. However, the hazardous breaking wave conditions previously at the entrance would be present further inside the harbor. Additionally, these breaking waves would tend to be higher than those presently at the entrance, since increasing channel depth allows more wave energy to enter the harbor.

Effects of Entrance Channel Dredging at Morro Bay, California

: This is a study using mathematical models to determine the wave response of two proposed plans of improvement to the shallow draft harbor at Kawaihae, Hawaii. The existing harbor consists of an 850-ft-long, 120-ft-wide entrance channel, a 1.2-acre turning basin, and an 850-ft-long breakwater. Plan 1 includes a 640-ft-long, 80-ft-wide main access channel, a 375-ft-long extension to the existing 850-ft-long west breakwater with a 200-ft-long stub on the harbor side, a 425-ft-long access breakwater with a 400-ft-long wave absorber, a 1,025-ft-long east breakwater, and a 650-ft-long offshore breakwater. Plan 2 includes the same improvements as Plan 1 with the exception of the removal of 200 ft of the west breakwater tip. These plans were developed to provide protection to the existing harbor. Study results indicated that Plan 1 met the requirements to protect the harbor adequately from the incident wave climate. It was determined that this plan will keep the wave height in the harbor berthing areas at 1 ft or lower and in the harbor channels and turning basin at 2 ft or lower approximately 90% of the time per year.

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Wave Response of Proposed Improvements to the Shallow-Draft Harbor at Kawaihae, Hawaii

As waves travel into harbors from deep water, nonlinear processes lead to transfers of energy from the wind wave frequencies to long waves with periods of the order of several minutes. If the periods of these long waves correspond with resonant periods of the harbor, harbor oscillations can produce dangerous navigation and mooring conditions. In 1988 a Coast Guard vessel was entering a drydock in Barbers Point harbor on the island of Oahu when they both sustained damage due to harbor seiching under relatively calm conditions outside the harbor. Transfer functions of harbor response to long period energy from physical and numerical models are compared to actual harbor measurements. The availability of physical, numerical, and field measurements provides an excellent example of good coastal engineering practice in the design and modification of harbors.

Linda S. Lillycrop

Papers

Physical and Numerical Model Studies of Barbers Point Harbor, Oahu, Hawaii

Barbers Point Harbor, Oahu, Hawaii monitoring study

Effects of Entrance Channel Dredging at Morro Bay, California

Wave Response of Proposed Improvements to the Shallow-Draft Harbor at Kawaihae, Hawaii

Comparison of Model and Field Results for Barbers Point Harbor