• Journal of Ocean Engineering and Technology
• /
• v.19 no.6 s.67
• /
• pp.16-21
• /
• 2005

In the design of super tankers or LNG carriers, which transport a large amount of liquid in the cargo tanks, the structural d11mage due to liquid sloshing is an important problem. The impact pressure from sloshing is most violent when the liquid motion of a partially filled tank is in resonance with the motion of a ship. In this study, the sloshing natural periods of a baffled tank, often installed to reduce liquid motion, is analyzed. A variational method is adopted to estimate the sloshing natural periods for a prismatic cargo tank with baffles of arbitrary filling depth of liquid; the results are compared with Lloyd's Register regulations on sloshing periods. In this study, using an effective liquid-fill-depth concept, sloshing periods for a baffled tank can be expressed by the same form as rectangular prismatic tanks without baffles. In contrast to Lloyd's Register regulations, which can be applicable only to cargo tanks with constant baffle size and distribution, the present results can be applicable to cases of variable baffle size and distribution.

• Journal of Ocean Engineering and Technology
• /
• v.8 no.2
• /
• pp.93-104
• /
• 1994

Recently in the design of super tankers or LNG carriers which transport a large amount of liquid in the cargo holds, the structural damage due to liquid sloshing becomes an important problem. The impact pressure from sloshing is most violent when the liquid motion of a partially filled tank is in resonance with the motion of a ship. In this paper the sloshing natural periods in liquid cargo tanks are estimated for partially filled tanks with various geometries. Especially the sloshing periods of baffled tanks which are often installed to reduce liquid motion and sloshing forces are calculated. A variational method is adopted to analyze the baffled tank of arbitrary filling depth of liquid. In this approach the liquid domain is divided into several subdomains in which the analytic solutions are potential energy are calculated from the velocity potentials in eachsubdomain. By minimizing the Hamilton's functional, the sloshing natural periods are estimated and the results are compared with experimental and numerical results.

• Journal of the Society of Naval Architects of Korea
• /
• v.54 no.5
• /
• pp.361-367
• /
• 2017

A membrane type LNG cargo tank is equipped with a pump tower and a liquid dome for loading and unloading of LNG. However, the membrane running continuously on the tank wall to prevent leakage of LNG is interrupted by the liquid dome, hence care should be taken in the design of liquid dome and its substructures. In case of GTT NO96 membrane type cargo containment system, chair structure is arranged along the periphery of the liquid dome targeting to support the membrane which is exposed to the both hull girder and thermal load. This paper proposes a new and simple chair structure, which outperforms traditional design from productivity point of view maintaining same level of structural safety. Strength assessment on the new design was performed to guarantee the structural safety of the new design, which includes strength, fatigue and crack propagation analysis.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.6 no.1
• /
• pp.132-150
• /
• 2014

In this study, the inertial properties of fully filled liquid in a tank were studied based on the potential theory. The analytic solution was obtained for the rectangular tank, and the numerical solutions using Green's 2nd identity were obtained for other shapes. The inertia of liquid behaves like solid in recti-linear acceleration. But under rotational acceleration, the moment of inertia of liquid becomes small compared to that of solid. The shapes of tank investigated in this study were ellipse, rectangle, hexagon, and octagon with various aspect ratios. The numerical solutions were compared with analytic solution, and an ad hoc semi-analytical approximate formula is proposed herein and this formula gives very good predictions for the moment of inertia of the liquid in a tank of several different geometrical shapes. The results of this study will be useful in analyzing of the motion of LNG/LPG tanker, liquid cargo ship, and damaged ship.

• Special Issue of the Society of Naval Architects of Korea
• /
• 2017.10a
• /
• pp.93-104
• /
• 2017

IMO type C independent tank is one of the cargo containment system specified on IGC code. It is normally adopted for small and medium size liquefied gas carrier's cargo containment system and it can be applied to fuel tank of LNG fueled vessel. This study focuses on rule scantling process and evaluation methods in early design stage of type C independent tank. Actual design results of 22K LPG/Ammonia/VCM carrier's No.2 cargo tank are demonstrated. This paper presents the calculation methods of design acceleration and liquid height for internal design pressure as defined on IGC code. And this paper shows the applied results of classification rules about shell thickness requirement and buckling strength. Additionally this paper deals with evaluation methods of structural strength and cumulative fatigue damage using FE analysis.

• Special Issue of the Society of Naval Architects of Korea
• /
• 2005.06a
• /
• pp.22-30
• /
• 2005

Sloshing loads, produced by the violent liquid free-surface motions inside the cargo tank have become an important design parameter in ship building industry since there have been demands for the increased sizes of the cargo containment system of LNG carriers. In this study, sloshing impact pressure acting on the shell of the spherical cargo tank of an LNG carrier as well as dynamic pressure and flow behavior around the pump tower located at the center of the tank have been calculated. Comparative numerical sloshing simulations for a spherical LNG tank using 2-D LR.FLUIDS which is based on the finite difference method and 3-D MSC.DYTRAN which is capable of calculating nonlinear fluid-structure interaction have been carried out. A method of calculating sloshing-induced dynamic loads and the subsequent structural strength analysis for pump tower of a spherical LNG carrier using MSC. DYTRAN and MSC.NASTRAN have been presented.

• Journal of the Society of Naval Architects of Korea
• /
• v.46 no.6
• /
• pp.650-658
• /
• 2009

Two dimensional sloshing phenomena in regularly excited liquid cargo tank are numerically simulated with finite difference method. Navier-Stokes equations and continuity equation are computed for this study. The free-surface is determined every time step satisfying kinematic boundary condition using marker-density method. And the exciting force is treated by adding the acceleration of the tank to source term. The results are compared with other existing experiment results. And the comparison results show a good agreement. The sloshing phenomena in the tank of the 138K LNG carrier in sway motion is simulated with present calculation methods in low filling level. To find the relations between impact pressure and excitation condition, the calculations are performed in various amplitudes and periods. The averaged maximum pressures are compared each other.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 1997.11a
• /
• pp.203-210
• /
• 1997

Reports of explosions in cargo and storage tanks of high flash point liquids such as residual fuel oil, asphalt, and oily waste water have shown that these explosions have occurred even when the liquid temperatures are well below the liquid nominal flash point. The reasons for these seemingly paradoxical explosions are reviewed and results of recent laboratory tests are presented to better define the conditions leading to flammable vapor atmospheres in these tanks. The potential effectiveness of various prevention measures are discussed including inerting, monitoring tank vapor concentrations, and periodic cleaning of condensation and deposits on the tank walls and roof.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.18 no.3
• /
• pp.341-346
• /
• 2008

This paper is to develop a monitoring system with diagnosis for smart cargo sensors that is for management and maintenance of the liquid cargo ships. The main goal of the system is to achieve the total automation system of the cargo sensor. By this study, the active smart sensor for the liquid cargo ships is designed and developed that guarantees high-confidence, stability, and durability. The proposed system consists of a monitoring part of the steam pressure, high-level monitoring, over flowing monitoring, gas monitoring, and tank temperature monitoring. The signals transferred from each unit system are used for sensor diagnosis based on confidence and accuracy. Finally, in this study, the total supervisory monitoring system is developed to maintain and manage the cargo effectively based on fault diagnosis and prognosis of the each sensor system.

• Journal of the Korean Institute of Navigation
• /
• v.10 no.2
• /
• pp.139-155
• /
• 1986

In this paper the dynamic effects due to the free water motions in tanks upon the lateral motion of a floating body in regular waves are calculated, in order to obtain the relationship between a motion of a floating body and that of the free water in tanks. Under the assumption that the fluid is ideal and motion amplitudes are small, velocity potential of the fluid in tanks is calculated by the source distribution method and the hydrodynamic forces and moments are calculated by the integration of fluid pressures over the tank surface. Hydrodynamic effects of the fluid on the floating body are expressed in terms of added mass and coupling coefficient obtained from the integration. Computations are carried out for ship with seven wide center tanks and comparisons between the liquid cargo loading case and the rigid cargo loading case are shown.