• Journal of Ocean Engineering and Technology
• /
• v.10 no.3
• /
• pp.96-104
• /
• 1996

Hamilton's principle is used to derive Euler-Lagrange equations for free surface flow problems of incompressible ideal fluid. The velocity field is chosen to satisfy the continuity equation a priori. This approach results in a hierarchial set of governing equations consist of two evolution equations with respect to two canonical variables and corresponding boundary value problems. The free surface elevation and the Lagrange's multiplier are the canonical variables in Hamilton's sense. This Lagrange's multiplier is a velocity potential defined on the free surface. Energy is conserved as a consequence of the Hamiltonian structure. These equations can be applied to waves in water of finite depth including generalization of Hamilton's equations given by Miles and Salmon.

• Journal of Ocean Engineering and Technology
• /
• v.31 no.4
• /
• pp.257-265
• /
• 2017

In this study, a series of numerical simulations was conducted in order to design a truncated mooring line with a static similarity to the prototype. A finite element method based on minimizing the potential energy was utilized to describe the dynamics of mooring lines. The prototype mooring lines considered were installed at a water depth of 1,000 m, whereas the KRISO ocean engineering basin (OEB) in Daejeon has a water depth of 3.2 m, which represents 192 m using a scaling of 1:60. First, an investigation for the design of the truncated mooring line was carried out to match the static characteristics of the KRISO Daejeon OEB environment. Then, the same procedure was performed with the KRISO new deepwater ocean engineering basin (DOEB) that is under construction in Busan. This new facility has a water depth of 15 m, which reflects a real scale depth of 900 m considering the 1:60 scaling factor. A finite element method was used to model the mooring line dynamics. It was found that the targeted truncated mooring line could not be designed under the circumstances of the KRISO OEB with any material properties, whereas several mooring lines were easily matched to the prototype under the circumstances of the KRISO DOEB.

• Journal of applied mathematics & informatics
• /
• v.23 no.1_2
• /
• pp.127-140
• /
• 2007

We present the boundary value problem (BVP) for the heave motion due to a vertical circular cylinder in water of finite depth. The BVP is presented in terms of velocity potential function. The velocity potential is obtained by considering two regions, namely, interior region and exterior region. The solutions for these two regions are obtained by the method of separation of variables. The analytical expressions for the hydrodynamic coefficients are derived. Computational results are presented for various depth to radius and draft to radius ratios.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.1
• /
• pp.108-117
• /
• 1998

This study was performed to analyze the fluid flow characteristics and the temperature distribution of the aquarium for fish breeding. In this study, the finite volume method and turbulence k-$\varepsilon$ model with the SIMPLE computational algorithm are used to study the water flow in the aquarium. The calculation parameters are the circulating flow rate and the basin depth, and the experiments were carried out for the water flow visualization This numerical analysis gives reasonable velocity distributions in good agreement with the experimental data. As the results of the three dimmentional simulations, the sectional mean velocity increased as the sectional mean temperature increases for constant basin depth, and the mean velocity increased more rapidly for small basin depth than that of large basin depth, The mean velocity and temperature can be expressed as the function of the circulating flow rates and the basin depth.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2004.11a
• /
• pp.29-34
• /
• 2004

Numerical and experimental studies on pipeline laying for intake Deep Ocean Water are carried out. In the numerical study, an implicit finite difference algorithm is employed for three-dimensional pipe equations. Fluid non-linearity and bending stiffness are considered and solved by Newton-Raphson iteration. Seabed is modeled as elastic foundation with linear spring and damper. Top tension and general configuration of pipeline at a depth are predicted. It is found that control for tension to prevent being large curvature of pipeline is needed on th steep seabed and, it should be considered 23.5 ton of tension at a top of pipe on the process of pipeline laying at 400m of water depth The largest top tension of pipe on condition of the beam sea during pipe laying is shown from the experiment. The results of this study can be contributed to the design of pipeline laying for upwelling deep ocean water.

• Journal of the Society of Naval Architects of Korea
• /
• v.42 no.1 s.139
• /
• pp.18-23
• /
• 2005

The transmission and reflection coefficiencies of a BBDB-type floating breakwater in water of finite depth are studied taking account of fluctuating air pressure in the air chamber. The wave potential is calculated by a hybrid integral equation consisting of a Green integral equations associated with the Rankiue Green function inside the BBDB and the Kelvin Green function outside. The transmission and reflection coefficients of the breakwater are obtained directly from the potential solution in the outer region.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.24 no.4
• /
• pp.1-8
• /
• 1987

In this paper negative drift forces are discussed, which act on a two-dimensional cylinder exposed to slightly modulated waves in water of finite depth. By combining matched asymptotic expansion method with multiple scale technique, it is clearly shown that the slowly-varying drift force can be negative under certain circumstances: i) Incident waves are irregular or slightly modulated. ii) The water depth is finite compared to the wave length of carrier waves. iii) The gap between the keel of the cylinder and ocean floor is narrow. Then the negative drift forces are caused by the unbalance of hydrostatic force associated with set down. Real fluid and wave breaking effects are not considered.

• Journal of Ship and Ocean Technology
• /
• v.4 no.2
• /
• pp.24-37
• /
• 2000

The purpose of this paper is to study the upstream waves in front of an advancing arbitrary hull shape in a restricted water channel. Conventionally, in a restricted water channel, shallow water effects are amplified because of the finite water depth and width. When the effects of shallow water and the restricted channel width are severe, upstream waves propagate forward from the fore-body of the advancing hull. In this study, numerical simulations are carried out for the relevant analysis of the flow phenomena by the draft variation of advancing hull in a restricted water channel. Numerical simulations are done with a finite-difference method based on the MAC scheme in a rectangular grid system.

• Structural Monitoring and Maintenance
• /
• v.6 no.2
• /
• pp.85-101
• /
• 2019

The effects of foundation scour depth and riverbed condition on the natural frequencies of a typical cross-river integral abutment bridge have been studied. The conventional operational modal analysis technique has been employed in order to extract the modal properties of the bridge and the results have been used in the Finite Element (FE) model updating procedure. Two tests have been carried out in two different levels of water and wet condition of the riverbed. In the first test, the riverbed was in dry condition for two subsequent years and the level of water was 10 meter lower than the natural riverbed. In the second test, the river was opened to water flow from the upstream dam and the level of water was 2 meter higher than the natural riverbed. The results of these two tests have also been used in order to find to what extend the presence of water flow in the river and saturation of the surrounding soil affect the bridge natural frequencies. Finally, the updated FE model of the bridge has been applied in a series of parametric analyses incorporating the effect of piles' relative scour depth on the bridge natural frequency of the first four vibration modes.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.15 no.1
• /
• pp.1-6
• /
• 1978