Modified mild slope equation and open boundary conditions

A numerical model to compute wave field is developed. It is based on the Berkhoff diffraction-refraction equation, in which an energy dissipation term is added, to take into account the breaking and the bottom friction phenomena. The energy dissipation function, by breaking and by bottom friction, is introduced in the Berkhoff equation to obtain a new equation of propagation.The resolution is done with the hybrid finite element method, where lagrangians elements are used.     

An experimental study on non-linear progressive wave-induced dynamic stresses in seabed

In this study, the dynamic stresses within the seabed induced by non-linear progressive waves were explored through a series of hydraulic model tests on a movable bed within a wave flume. By comparing Stokes’ 2nd-order wave theory with the theory of wave-induced dynamic stresses within the seabed as proposed by Yamamoto et al. [1978. On the response of a poro-elastic bed to water waves. Journal of Fluid Mechanics 87 (1), 193–206.] and Hsu and Jeng [1994. Wane-induced soil response in an unsaturated anisotropic seabed of finite thickness. International Journal for Numerical and Analytical Methods in Geomechanics 18, 785–807], the experimental results show that the pressure on the seabed surface, the pore water pressure within the seabed as well as the vertical and the horizontal stresses are all smaller than their theoretical values. If we were to obtain the characteristics of seabed soil, the analytical solution of Hsu and Jeng [1994. Wane-induced soil response in an unsaturated anisotropic seabed of finite thickness. International Journal for Numerical and Analytical Methods in Geomechanics 18, 785–807] might agree to the simulation of the wave-induced effective stresses and shear stress in the sandy seabed. A different phase shift exists among all the three soil stresses. Their influences on the three dynamic stresses within seabed soil are important for seabed stability, and can be used in the verification of numerical models. In the whole, the non-linear progressive waves and the naturally deposited seabed are found to have a strong interaction, and the behavior of the induced dynamic stresses within the seabed is very complicated, and should be investigated integrally.     

Three‐dimensional simulation of tsunami run‐up around conical island

At the circular Babi Island in the Flores tsunami (1992) and pear shaped island in the Okushiri event (1993), unexpectedly large tsunami run‐up heights in the lee of conic islands were observed. The flume and basin physical model studies were conducted in the Coastal Hydraulic Laboratory, Engineering Research and Development Center, U.S. Army Corps of Engineers to provide a better understanding of the physical phenomena and verify numerical models used in predicting tsunami wave run‐up on beaches, islands, and vertical walls. Reasonably accurate comparison of run‐up height of solitary waves on a circular island has been obtained between laboratory experimental results and two‐dimensional computation model results. In this study we apply three‐dimensional RANS model to simulate wave run‐up on conical island. In the run‐up computation we obtain that 3D calculations are in very good comparison with laboratory and 2D numerical results. A close examination of the three‐dimensional velocity distribution around conical island to compare with depth‐integrated model is performed. It is shown that the velocity distribution along the vertical coordinate is not uniform: and velocity field is weaker in the bottom layer and higher on the sea surface. The maximum difference (about 40%) appears at the time when solitary wave reached the circular island.     

Influence of large-diameter pipe pile driving on surrounding marine soils and adjacent submarine pipelines

Abstract

With the large-scale development and utilization of ocean resources and space, it is inevitable to encounter existing submarine facilities in pile driving areas, which necessitates a safety assessment. In this article, by referring to a wharf renovation project as a reference, the surrounding soil response and buried pipe deformation during pile driving in a near-shore submarine environment are investigated by three-dimensional (3D) numerical models that consider the pore water effect. Numerical studies are carried out in two different series: one is a case of a single pile focusing on the effect of the minimum plane distance of the pile–pipe, and the other is a case of double piles focusing on the effect of the pile spacing.     

Biocorrosion by Bivalves

Abstract. A survey of the historical background of chemically boring bivalves and the proposed methods of boring, indications for biocorrosion, observations, and experimental results are provided. The regional impact to the ecosystem is discussed with examples from the N. Adriatic, Caribbean, and E. Pacific. The fossil record of the geologically oldest biocorroders extends back into the Mesozoic, i.e ., U. Triassic for Lithophaga and Jurassic for gastrochaenids.     

Implementation of High Resolution Tidal Current Fields in Electronic Navigational Chart Systems

A system for displaying tidal currents in an electronic chart display and information system (ECDIS) has been developed and implemented in compliance with the standards of the International Hydrographic Organization (IHO). The tidal current fields can be displayed in real time on the electronic navigational chart and several options and functions for updating and zooming have been designed. The current fields are calculated from a data base with the harmonic constants for the four major tidal constituents. The harmonic constants are obtained from a high resolution numerical model with horizontal grid resolution of 100 m. The model is validated by comparing with sea level and current measurements. The depth matrix for the central part of the model domain was calculated from data from multibeam bathymetric surveys. An application example of the implementation is given for Trondheimsleia, a part of the main sailing route along the western coast of Norway.