• Structural Engineering and Mechanics
• /
• 제68권1호
• /
• pp.1-15
• /
• 2018

In ocean industry, free surface type ART (Anti Roll tank) system has been widely used to suppress the roll motion of floating structures. In those, various obstacles have been devised to obtain the sufficient damping and to enhance the controllability of freely rushing water inside the tank. Most of previous researches have paid on the development of simple mathematical formula for coupled ship-ARTs analysis although other numerical and experimental approaches exist. Little attention has been focused on the use of 3D panel method for preliminary design of free surface type ART despite its advantages in computational time and general capacity for hydrodynamic damping estimation. This study aims at developing a potential theory based hydrodynamic code for the analysis of floating structure with baffled ARTs. The sloshing in baffled tanks is modeled through the linear potential theory with FE discretization and it coupled with hydrodynamic equations of floating structures discretized by BEM and FEM, resulting in direct coupled FE-BE formulation. The general capacity of proposed formulation is emphasized through the coupled hydrodynamic analysis of floating structure and sloshing inside baffled ARTs. In addition, the numerical methods for natural sloshing frequency tuning and estimation of hydrodynamic damping ratio of liquid sloshing in baffled tanks undergoing wave exiting loads are developed through the proposed formulation. In numerical examples, effects of natural frequency tuning and baffle ratios on the maximum and significant roll motions are investigated.

• Coupled systems mechanics
• /
• 제4권4호
• /
• pp.317-336
• /
• 2015

The present paper deals with the analysis of water tank with elastic separator wall. Both fluid and structure are discretized and modeled by eight node-elements. In the governing equations, pressure for the fluid domain and displacement for the separator wall are considered as nodal variables. A method namely, direct coupled for the analysis of water tank has been carried out in this study. In direct coupled approach, the solution of the fluid-structure system is accomplished by considering these as a single system. The hydrodynamic pressure on tank wall is presented for different lengths of tank. The results show that the magnitude of hydrodynamic pressure is quite large when the distances between the separator wall and tank wall are relatively closer and this is due to higher rotating tendency of fluid and the higher sloshed displacement at free surface.

• Wind and Structures
• /
• 제18권3호
• /
• pp.267-279
• /
• 2014

Hydrodynamic analyses of classic and truss spar platforms for floating offshore wind turbines (FOWTs) were performed in the frequency domain, by considering coupling effects of the structure and its mooring system. Based on the Morison equation and Diffraction theory, different wave loads over various frequency ranges and underlying hydrodynamic equations were calculated. Then, Response Amplitude Operators (RAOs) of 6 DOF motions were obtained through the coupled hydrodynamic frequency domain analysis of classic and truss spar-type FOWTs. Truss spar platform had better heave motion performance and less weight than classic spar, while the hydrostatic stability did not show much difference between the two spar platforms.

• Journal of Advanced Research in Ocean Engineering
• /
• 제1권1호
• /
• pp.55-62
• /
• 2015

Floating structure such as tension leg platform, semi-submersible and spar are widely used in field of oil exploration and renewable energy system. All of these structures have the base cylinder support structure which have effective rule in overall dynamic of response. So the accurate and reliable modeling is needed for optimum design and understanding the physical background of these systems. The aim of this article is an analytical discussion on stochastic modeling of floating cylinder based support structure but an applicable one. Due to this a mathematical mass-damper-spring system of a floating cylinder of HAWAII WTG offshore wind as an applicable and innovative system is adopted to model a coupled degrees using random vibration in analytical way. A fully develop spectrum is adopted to solve the stochastic spectrum analytically by a proper approximation. Some acceptable assumption is adopted. The simplified but analytical and innovative hydrodynamic analysis of this study not only will help researcher to concentrate more physically on hydrodynamic analysis of floating structures but also can be useful for any quick, simplified and closed form analysis of a complicated problem in offshore engineering.

• Coupled systems mechanics
• /
• 제10권6호
• /
• pp.491-507
• /
• 2021

The aim of this paper is to conduct a hydrodynamic analysis of fluid flow over different weir types using the analytical solution, the physical model taken from another article, and numericalsimulations through the Smoothed particle hydrodynamic method (SPH) using the compiled DualSPHysics source code. The paper covers the field of real fluid dynamics that includes a description of different proposed types of weirs in various flow regimes and the optimal solution for the most efficiency structure shape. A detailed presentation of the method, the structure and it's characteristics are included. Apart from the single stepped weir, two other weir types are proposed: a Divided type and a Downstream slopped type. All of them are modeled using the SPH method.

• 한국지진공학회논문집
• /
• 제22권3호
• /
• pp.139-147
• /
• 2018

In the present study, effective hydrodynamic pressure modeling methods for three-dimensional earthquake safety analysis of a dam intake tower structure are investigated. Time history analysis results using the Westergaard added mass and Chopra added mass methods are compared with the one by the CASI (Coupled Acoustic Structural Interaction) method, which is accepted as giving almost exact solutions, to evaluate the difference in displacement response, stress and dynamic eccentricity. The 3D time history analysis of a realistic intake tower, which has the standard geometry widely used in Korea, shows that the Chopra added mass method gives similar results in displacement and stress and less conservative results in dynamic eccentricity to CASI ones, while the Westergaard added mass yields much more conservative results in all measures. This study suggests to use the CASI method directly for three-dimensional earthquake safety analysis of a dam intake tower, if computationally possible.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제11권1호
• /
• pp.178-201
• /
• 2019

The appropriate design of a mooring system to maintain the position of an offshore structure in deep sea under various environmental loads is important. Fatigue design of the mooring line considering OPB/IPB(out-of-plane bending/in-plane bending) became an essential factor after the incident of premature fatigue failure of the mooring chain due to OPB/IPB in the Girassol region in West Africa. In this study, mooring line fatigue analysis was performed considering the OPB/IPB of a spread moored FPSO in deep sea. The tension of the mooring line was derived by hydrodynamic analysis using the de-coupled analysis method. The floater motion time histories were calculated under the assumption that the mooring line behaves in quasi-static manner. Additional time domain analysis was carried out by prescribing the obtained motions on top of the selected critical mooring line, which was determined based on spectral fatigue analysis. In addition, nonlinear finite element analysis was performed considering the material nonlinearities, and both the interlink stiffness and stress concentration factors were derived. The fatigue damage to the chain surface was estimated by combining both the hydrodynamic and stress analysis results.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집A
• /
• pp.475-480
• /
• 2000

The transient dynamic-response analysis of fuel-storage tanks of flying vehicles accelerating in the vertical direction is achieved with finite element method. A fuel-storage tank is a representative example of the fluid-structure interaction problem, in which structure and fluid media interact strongly. For the accurate analysis of this complicated fluid-structure system, we employed ALE(arbitrary Lagrangian-Eulerian) coupling method. Two types of fuel-storage tanks, one with two baffles and the other without baffle, are considered to examine the effect of baffles. The fuel-storage tank with baffles shows more uniform hydrodynamic pressure distribution, resulting effective stress in structural region and faster convergence from transient to steady states. MSC/Dytran, a commercial FEM software for the 3D coupled dynamic analysis, is used for this analysis.

• 소음진동
• /
• 제7권4호
• /
• pp.655-661
• /
• 1997

건물내 동적계가 수중에 있고 유체동적효과가 클 경우, 건물을 지진절연하면 일반적인 경향과는 달리 계의 지진응답이 오히려 증가될 수 있다. 본 논문에서는 건물내 수조에 잠긴 계에 대하여 단순화된 복합모델의 동적해석을 통하여 건물의 지진절연이 건물내 수중계의 지진응답에 어떻게 그리고, 최대로 얼마나 영향을 주는지를 보인다. 이 때 응답을 줄이기 위한 내진설계방안으로서 유체질량효과를 조절하는 유체간극의 최적화를 수행하여 그 효과를 살펴보았고, 간극조절이 곤란한 경우의 대안으로서 지진절연된 건물내 수중계를 다시 지진절연하는 방안을 제안하였으며 적절한 이중절연방식의 조합에 대한 효율을 비교하였다.

• 한국안전학회지
• /
• 제15권3호
• /
• pp.96-101
• /
• 2000

The effects of internal fluid motion have to be considered in the analysis of liquid storage containers. Therefore this thesis developed a three-dimensional boundary element-finite element method for the analysis of rectangular liquid storage containers. The irrotational motion of inviscid and incompressible ideal fluid is modeled by using boundary elements and the motion of structure by finite elements. Coupling is performed by using compatibility and equilibrium conditions along the interface. Dynamic response characteristics of rectangular liquid storage containers such as sloshing motion, hydrodynamic pressure, displacement by fluid-structure interaction are investigated.