Journal of Waterway, Port, Coastal, and Ocean Engineering

Wave information is generated for the population of tropical cyclones that affects the Great Barrier Reef region. Several models are combined to create a wave database at 150,000 locations at a resolution of 1,500 m throughout this large and remote region. An autoregressive time series model, based on historical data, generated time series of position and central pressure for a very large ensemble of synthetic tropical cyclones. An empirical model was used to create the wind field throughout the wave generating area. The wind field had three components: The primary cyclone vortex, a secondary vortex used to model the low-pressure trough in which a cyclone is often embedded, and the external synoptic scale wind field created between the cyclone and the mid latitude high-pressure systems. WAMGBR, a wave generation model especially adapted for conditions in the Great Barrier Reef, was used to simulate a very large ensemble of storms on a nested grid system in transformed spherical coordinates. The results of the study are significant wave heights, peak periods, and mean directions for return periods between 20 and 1,000 years.

A three-dimensional (3D) hydrodynamic model application to the Bay of Fundy was performed using a boundary-fitted coordinate hydrodynamic model. Because the Saint John River and Harbour area were of interest for this study, a very fine grid with a resolution range of 50–100 m was used in the Saint John Harbour region, while a grid resolution of about 2–3 km was used in the Bay of Fundy. The model forcing functions consist of tidal elevations along the open boundary and fresh water flows from the Saint John River. The model-predicted surface elevation compares well with the observed surface elevation at Saint John and the root mean square error in the model-predicted surface elevation for a 60-day period is found to be 4%. The amplitudes and phases of the major tidal constituents at 24 tidal stations, obtained from a harmonic analysis of a 60-day simulation, compares well with the observed data obtained from Canadian Hydrographic Survey. The predicted harmonic amplitudes and phases of the $M_2$ tidal constituent are, respectively, within 20 cm and 7° of the observed data. The counterclockwise gyre observed in the body of Bay of Fundy is reproduced in the model.

An improved curvilinear grid model based on fully nonlinear Boussinesq equations is used to simulate wave propagation in Ponce de Leon Inlet, Fla. We employ the nearshore bathymetry of Ponce de Leon Inlet and generate a stretched curvilinear grid that can resolve shortwaves in the nearshore region and fit the complex geometry. Simulations of 18 cases with monochromatic input waves and Texel-Marsden-Arsloe spectral waves are carried out on the same scale as in the 1:100 scale physical model conducted at the U.S. Army Engineer Research and Development Center. Wave height comparisons, time series comparisons of surface elevation for monochromatic wave cases, and comparisons of power spectrum for spectral wave cases are made between numerical results and laboratory measurements. Comparison is also made between the probability distribution of surface elevation and skewness and asymmetry measures for both the measured data and the Boussinesq model results. It is shown that for the computations of nonlinear wave transformation over irregular bathymetry, the Boussinesq model is able to predict nonlinear wave features and is thus a more accurate model than some conventional models in shallow water.

Laboratory experiments were conducted in a wave flume to measure wave conditions (height, period, and kinematics) that caused movement of submerged ordnance and cylinders. Laboratory results were analyzed and two empirical theories were developed for predicting movement based on wave conditions and ordnance/cylinder characteristics: (1) modified Shields parameter approach comparing ordnance and cylinder parameters with a wave Shields parameter to identify critical regimes for ordnance/cylinder movement; and (2) Keulegan-Carpenter number (KC) approach comparing the ratio of maximum orbital velocity at the ordnance/cylinder surface and ordnance/cylinder diameter with relative water depth. Evaluation of these two approaches with the laboratory data indicated that the best predictive technique appeared to be the modified Shields parameter approach. A field deployment of two drogue cylinders instrumented with acoustic pingers was conducted to further investigate ordnance movement using acoustic tracking procedures. Measured wave conditions and cylinder characteristics were used in the modified Shields parameter approach and indicated that the cylinders would be mobile. The field deployment of two cylinders verified the prediction results showing net movements of 15 and 13 m, respectively.

This paper investigates and compares four simple, continuous equations that can potentially make useful estimates of fall velocity. These estimates span the range of laminar, transitional, and turbulent flow regimes. All equations take advantage of the fact that the fall velocity Reynolds number is a function of only one variable, the Archimedes buoyancy index. Adjusting the coefficients can make a significant improvement in the fit of these equations to data. In the commonly used beach equilibrium profile model, $h=A_p{x}^{2/3}\text{,}$ the sediment scale parameter $A_p\text{,}$ is usually tabulated as a function of grain diameter. It will be shown that the normalized sediment scale parameter $A_p/d^{1/3}$ is also a function of only the Archimedes buoyancy index. This research indicates that the Archimedes buoyancy index is the fundamental independent variable for both the fall velocity Reynolds number and the normalized sediment scale parameter. Calculating the Archimedes buoyancy index is facilitated by some simple equations, which in turn allow easy computation of fall velocity and sediment scale parameter.