Waves

PURPOSE: The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to demonstrate the use of BOUSS-2D in three example applications. The BOUSS-2D is a Boussinesq wave model that is now part of the U.S. Army Corps of Engineers (USACE) Surface-Water Modeling System (SMS). Demirbilek et al. (2004) gives a detailed description of the SMS interface of BOUSS-2D. This second technical note in BOUSS-2D series is a step-by-step tutorial that shows the usage of the model through illustrative examples. The next CHETN in the series will describe the time-series and frequency-domain analysis utilities and techniques developed for post-processing BOUSS-2D model results. Details of the BOUSS-2D model theory, numerical implementation, and example applications are presented in a technical report (Nwogu and Demirbilek 2001). BACKGROUND: As a phase-resolving nonlinear wave model, BOUSS-2D can be used in the modeling of various wave phenomena including shoaling, refraction, diffr...

The Ground Penetrating Radar (GPR) method has been extensively used to map shallow subsurface features. Such kind of information is very important for different types of studies, ranging from archaeological to groundwater search. Almost all GPR surveys for groundwater exploration are usually conducted in sedimentary terrains. In this paper, we demonstrate the applicability of the GPR method in the exploration of underground water in a crystalline terrain. An example of fixed offset data collected at one known spring in the district of Petrópolis (Brazil) is given. Common Mid Point (CMP) data were also collected to estimate the velocity of the radar waves. The saturated region is clearly outlined in the GPR section as a zone of attenuation and inversion of the wavelet phase polarity.

Aims:The effects of ion and neutral drag forces on stability of low-frequency wave modes is investigated from the point of view of parameters relevant to the plasma environment in the vicinity of the main Saturn rings. The electrons and ions are considered to be magnetized and corotate with the planet, while the dust grains are not magnetized and move around the planet on Keplerian orbits. Methods: The wave modes of low-frequencies in such dusty plasma, propagating along the ring in the azimuthal direction are analyzed based on the susceptibilities derived from the standard fluid approach and model presentation of the drag forces valid in the parameter regime of the dusty plasma of planetary rings. Results: It is found that the ion drag force can crucially change the stability of dust-acoustic perturbations. Inside the co-rotation distance the ion drag force can be responsible for the excitation of dust-acoustic waves, while for the region outside the synchronous orbit this mode can hardy be excited (at radial distances corresponding to the main rings). The instability due to the ion drag force could be also of some importance for perturbations in remote rings, where the relative ion-dust velocities exceed their thermal speed.

The concept of equilibrium plan form and equilibrium profile has been widely used as an engineering tool in order to design beach nourishment projects. The scope of this paper is to further explore this “equilibrium beach” concept in crenulated bays, as a long-term tool for beach nourishment projects. The proposed methodology is based on González and Medina (2001) and combines the static equilibrium plan and profile for long-term analysis. This methodology includes a modified equilibrium plan form, which is able to define the orientation of the local wave front in the diffracting point, and also to locate the downcoast starting point of the static equilibrium beach from which the parabolic plan form of Hsu and Evans (1989) is valid. This methodology permits the application of any equilibrium profile formulation. An example of the application of this methodology and long-term formulations to the design of the Spanish nourishment project of Poniente Beach (Gijón) is presented. Ten years after its construction, the beach has still got a static equilibrium and remains pretty close to the predicted equilibrium beach in plan and profile.

This report documents a study performed for the U.S. Army Engineer District, Seattle to identify and evaluate feasible methods for reducing annual maintenance dredging in the outer Federal navigation channel at Grays Harbor, WA, by modification of the north jetty. Main interest was in potential reduction of southward sand bypassing the north jetty and preservation of the jetty should the neighboring beach erode. Considerable information and predictive capability were generated concerning the behavior of the Federal navigation channel and adjacent coastal and inlet shorelines. The study was conducted as a coordinated multi-disciplinary approach involving field measurement, physical modeling of the hydrodynamics and potential sediment pathways, geomorphic analysis and sediment budget formulation, and numerical modeling of waves, circulation and sediment transport, including modeling of shoreline change and bypassing. Numerous alternatives were considered and subjected to a screening p...

Wave overtopping nearshore coastal structures, such as shore-parallel breakwaters, can significantly alter the current circulation and sediment transport patterns around the structures, which in turn affects the formation of tombolos and salients in the nearshore area. This paper describes the implementation of a wave overtopping module into an existing depth-averaged coastal morphological mode: COAST2D and model applications to investigate the effect of wave overtopping on the hydrodynamics and morphodynamics around a group of shore-parallel breakwaters. The hydrodynamic aspects of the model were validated against a series of laboratory conditions. The model was then applied to a study site at Sea Palling, Norfolk, UK, where 9 shore-parallel segmented breakwaters including 4 surface-piercing and 5 low-crested breakwaters are present, for the storm conditions in Nov 2006. The model results were compared with laboratory data and field measurements, showing a good agreement on both hydrodynamics and morphological changes. Further analysis of wave overtopping effect on the nearshore hydrodynamics and morphodynamics reveals that wave overtopping has significant impacts on the nearshore circulation, sediment transport and the resulting morphological changes within such a complex breakwater scheme under the storm and macro-tide conditions. The results indicate the importance of including the wave overtopping in modelling nearshore morphodynamics with the presence of coastal structures.