Search

Recently, Rim et al. (Wave Motion 116:103063, 2023) proposed an exact Dirichlet-to-Neumann (DtN) boundary condition to study the water wave motion over undulated seabed by wave diffraction. This paper focuses on linear wave interaction with a bottom-mounted body near a vertical wall. The water domain is separated into an exterior subdomain and an interior one by a virtual cylindrical surface or so-called an artificial boundary which encloses not only the original body but also its imaginary one about the vertical wall. The wave interaction with the bodies in the interior subdomain is solved by using a boundary integral equation with an exact DtN operator on the artificial boundary which is derived from a velocity potential in the exterior subdomain. Upon successful verification of the present approach by comparison with the results of ANSYS AQWA for a bottom-mounted vertical circular cylinder near the wall, the model is extended to a vertical cylinder with cross section of rounded rectangle.

A method for estimating the system reliability of the ship grillage structure under combined axial compression and lateral pressure load is presented in this paper. The ship grillage structure is idealized as a structural system consisted of several longitudinal stiffeners and transverse girders with attached plating in parallel, respectively. The ultimate compressive strength of the stiffener with attached plating under the combined axial compression and lateral pressure load is calculated by the analytical method. The lateral pressure load applied to the ship grillage structure is considered how to be distributed on the longitudinal stiffener and the transverse girder. The reliability on the buckling collapse of each stiffener with attached plating is estimated by Monte Carlo simulation method, and the system reliability of the ship grillage structure is estimated, considering the redistribution of the external load in other stiffeners after any of stiffeners fails. The uncertainties are quantified using probabilistic models of design variables proposed in the previous literature. By numerical example for the system reliability estimation of a stiffened panel under combined axial compression and lateral pressure load, the present method is validated.

This paper is concerned with wave diffraction and radiation by an arbitrarily-shaped submerged body in front of a vertical wall. An artificial boundary is chosen as a virtual cylindrical surface so that it can enclose two bodies (one is the original body and another is its imaginary body by the method of mirror image), and the entire water domain is divided into an interior subdomain and an exterior one by the artificial boundary. An exact DtN artificial boundary condition on the artificial boundary is derived from an analytical solution in the exterior subdomain, and it is used as a boundary condition to solve hydrodynamic interaction of the bodies with the interior subdomain numerically using boundary integral equation. The present numerical model is validated by comparison with precedent analytical results in case of a submerged circular cylinder. The effects of heading angle, body submergence and distance from the wall on wave elevation and exciting forces are considered in case of a chamfer box or a capsule. [ABSTRACT FROM AUTHOR]

For the interaction between ocean wave and bottom-mounted structures, it is often required to introduce an artificial interface by which the fluid domain unbounded horizontally is divided into an interior subdomain with finite volume and an exterior one, to focus on the structures and the interior fluid subdomain only. In this paper, an artificial circular cylindrical surface and a novel Dirichlet-to-Neumann (DtN) map on it are suggested to close the constitutive equations in the interior subdomain since the top and bottom faces of the interior subdomain satisfy free surface condition and seabed condition, respectively. The DtN map is used as a boundary condition of the problem for the interior subdomain, which will be solved using the method of boundary integral equation (BIE). Upon successful validation for a bottom-mounted circular cylinder, the present method is extended to the cases of a single rounded-rectangular cylinder and an array of four cylinders mounted on a flat or undulated seabed to obtain three-dimensional wave elevation around them and to study the effects of fillet radius and incident angle on the wave force acting on each cylinder.

Artificial upwelling by the use of airlift pump is regarded as an effective way in utilizing deep ocean water and actualizing ocean fertilization. This paper focuses on numerical analysis of steady air–water two-phase flow in a vertical pipe of an airlift system based on one-dimensional multi-fluid model. The depth distributions of 6 physical quantities such as volumetric fractions and axial velocities of two phases, air density and pressure are calculated by solving the governing equations or by integrating the vector form of nonhomogeneous ordinary differential equation for two-phase flow interval. Upon successful verification of the present numerical model through a comparison with precedent theoretical and experimental results in case of a vertical pipe with length of 7.86 m, the model is extended to the case of artificial upwelling from water depth of 2000 m. The effects of submerged depth of air–water mixer on the pumped amount of water and the depth distributions of 6 physical quantities are considered. • This paper is concerned with numerical analysis of steady air–water two-phase flow in a vertical pipe of an airlift system to lift deep ocean water. • The depth distributions of 6 physical quantities such as volumetric fractions and axial velocities of two phases, air density and pressure are obtained from one-dimensional multi-fluid model. • The present model can be applied to predict the performance of airlift pump for lifting deep ocean water and the depth distributions of 6 physical quantities in axial direction. [ABSTRACT FROM AUTHOR]

This paper is concerned with three-dimensional water wave motion over undulated seabed. For the wave motion problem in seawater of finite depth, the fluid domain is usually unbounded horizontally but bounded vertically by free water surface and seabed which have their own boundary conditions. To study local wave motion over undulated region only, a novel Dirichlet-to-Neumann (DtN) boundary condition is suggested on an artificial circular cylindrical surface by which the fluid domain is divided into an interior region with finite volume and an exterior region. A unique solution of wave motion in the interior region is guaranteed by the novel boundary condition on the artificial cylindrical surface and the other boundary conditions on mean free water surface and undulated seabed. The solution is obtained by using Boundary Integral Equation (BIE) with all boundary conditions including the novel artificial boundary condition. Upon verification for a submerged square cylinder, the present model is extended to the case of an array of rounded-rectangular cylinders or circular paraboloidal shoals. • A novel DtN boundary condition on an artificial cylindrical surface is suggested to solve three-dimensional wave motion with undulated seabed. • Boundary Integral Equation (BIE) is implemented by boundary conditions including the DtN condition on the artificial boundary surface. • The wave elevations over 2 types of undulated seabeds are discussed. [ABSTRACT FROM AUTHOR]