• 대한조선학회논문집
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• 제47권5호
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• pp.681-688
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• 2010

During certification of freefall lifeboats, it is necessary to estimate the injury potential of the impact loads exerted on the occupants during water entry. This paper focused on the numerical simulation to predict the acceleration response during the impact of freefall lifeboats on the water using FSI(Fluid-Structure Interaction) analysis technique of LS-DYNA code. FSI problems could be conveniently simulated by the overlapping capability using Arbitrary Lagrangian Eulerian(ALE) formulation and Euler-Lagrange coupling algorithm of LS-DYNA code. Through this study, it could be found that simulation results were in relatively good agreement with experimental ones in the acceleration peak values, and that the loading conditions were very sensitive to the acceleration responses by the experimental and simulation results.

• 한국공간구조학회논문집
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• 제5권4호
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• pp.79-90
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• 2005

본 연구의 주 목적은 다양한 요인에 의해 케이블-막구조물에 요소이동이 발생할 때, 당초 해석 시 가정되었던 좌표나 응력상태의 변화에 대해 막과 케이블 사이에 발생하는 요소이동의 방향이나 크기를 산정하고, 요소이동이 발생한 후 응력상태의 변화를 규명하는 것이다. 먼저 케이블 보강 막구조물의 요소이동 문제를 해석하기 위한 이론적 배경인 ALE 유한요소법의 개념을 소개하고, ALE 개념이 도입된 케이블-막구조물에서의 요소이동을 고려한 강성매트릭스를 작성하여 해석 프로그램을 개발한다. 개발된 프로그램의 타당성을 검증하기 위해 다양한 예제 해석을 수행한다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 추계학술대회논문집
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• pp.150-156
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• 1995

In the finite element analysis of metal forming processes, the updated Lagrangian approach has been widely and effectively used to simulate the non-steady state problems. However some difficulties have arisen from abrupt flow change as in extrusion through square dies. In the present work, a ALE(arbitrary Lagrangian-Eulerian) finite element formulation for deformation analysis are presented for rigid viscoplastic materials. The developed finite element program is applied to the analysis of square die extrusion of a square section. The computational results are compared with those from the updated Lagrangian finite element analysis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.11-22
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• 1999

A numerical prediction method has been proposed to predict non-linear free surface oscillation in a three-dimensional container. The fluid motions are numerically predicted with Navier-Stokes equations discretized in a Lagrangian scheme with sufficient numerical accuracy. The profile of a free surface is precisely represented with three-dimensional body-fitted coordinates (BFC), which are regenerated in each computational step on the basis of the arbitrary Lagrangian-Eulerian (ALE) formulation. In order to confirm the reliability of the computational method, it was firstly applied to three-dimensional flows within complicated-shaped rigid boundaries, such as curved pipes and ducts. Than it was applied to benchmark computations related to free surface oscillations. Following these basic verifications, non-linear sloshings in a cylindrical tank and transitions from sloshing to swirling motions were numerically predicted. Throughout these computations, the applicability of the present computational method has been confirmed and some of the predicted free surface motions were visualized as sequential images and animations to understand their dynamic futures.

• 대한조선학회논문집
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• 제42권4호
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• pp.330-340
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• 2005

Compressible two-phase flow is analyzed based on the arbitrary Lagrangian-Eulerian (ALE) formulation. For water, Tamman type stiffened equation of state is used. Numerical fluxes are calculated using the ALE two-phase Godunov scheme which assumes only that the speed of sound and pressure can be provided whenever density and internal energy are given. Effects of the approximations of a material interface speed are Investigated h method Is suggested to assign a rigid body boundary condition effectively To validate the developed code, several well-known problems are calculated and the results are compared with analytic or other numerical solutions including a single material Sod shock tube problem and a gas/water shock tube problem The code is applied to analyze the refraction and transmission of shock waves which are impacting on a water-gas interface from gas or water medium.

• Korea-Australia Rheology Journal
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• 제18권2호
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• pp.109-118
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• 2006

A finite-element method was employed to analyze axisymmetric unsteady motion of a deformable bubble near the wall. In the present study a deformable bubble in a Newtonian medium near the wall was considered. In solving the governing equations a structured mesh generator was used to describe the collapse of highly deformed bubbles with the Arbitrary Lagrangian Eulerian (ALE) method being employed in order to capture the transient bubble boundary effectively. In order to check the accuracy of the present FE analysis we compared the results of our FE solutions with the result of the collapse of spherical bubbles in a large body of fluid in which solutions can be obtained using a 1D FE analysis. It has been found that 1D and 2D bubble deformations are in good agreement for spherically symmetric problems confirming the validity of the numerical code. Non-spherically symmetric problems were also solved for the collapse of bubble located near a plane solid wall. We have shown that a microjet develops at the bubble boundary away from the wall as already observed experimentally. We have discussed the effect of Reynolds number and distance of the bubble center from the wall on the transient collapse pattern of bubble.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.289-294
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• 2010

Numerical stud of an oscillating body in incompressible fluid is performed. Stabilized finite element method comprising of Streamline-Upwind/Petrov-Galerkin (SUPG) and Pressure-Stabilizing/Petrov-Galerkin (PSPG) formulations of linear triangular elements was employed to solve 2D incompressible Navier-Stokes equations whereas the motion of the body was considered by incorporating the arbitrary Langrangian-Eulerian(ALE) formulation. An algebraic moving mesh strategy is utilized for obtaining body conforming mesh deformation at each time step. Two tests cases, namely motion of a circular cylinder and of an airfoil in incompressible flow were analyzed. The model is first validated against the stationary cases and then the capability to handle moving boundaries is demonstrated.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.113-120
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• 2006

In this paper, generation mechanisms of ocean freak waves are briefly introduced in the context of wave-current interaction phenomena. As an accurate and efficient numerical tool, the spectral element method is presented with general features and specific treatment for the wave-current interaction problem. The present model of the fluid motion is based on the Navier-Stokes equations incorporating a velocity-pressure formulation. In order to deal with the free surface motion, an Arbitrary Lagrangian-Eulerian (ALE) description is adopted. As an intermediate stage of development, solution procedure and characteristic aspects of the present modeling and numerical method features are addressed in detail, and numerical results for wave-current interaction is left as further study.

• 대한기계학회논문집B
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• 제26권12호
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• pp.1738-1746
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• 2002

In the FSI (Fluid-Structure Interaction) problems, two different governing equations are to be solved together. One is fur the fluid and the other for the structure. Furthermore, a kinematic constraint should be imposed along the boundary between the fluid and the structure. We use the combined formulation, which incorporates both the fluid and structure equations of motion into a single coupled variational equation so that it is not necessary to calculate the fluid force on the surface of structure explicitly when solving the equations of motion of the structure. A two-dimensional channel flow divided by a Bernoulli-Euler beam is considered and the dynamic response of the beam under the influence of channel flow is studied. The Navier-Stokes equations are solved using a P2P1 Galerkin finite element method with ALE (Arbitrary Lagrangian-Eulerian) algorithm. The internal structural damping effect is not considered in this study and numerical results are compared with a previous work fer steady case. In addition to the Reynolds number, two non-dimensional parameters, which govern this fluid-structure system, are proposed. It is found that the larger the dynamic viscosity and density of the fluid are, the larger the damping of the beam is. Also, the added mass is found to be linearly proportional to the density of the fluid.

• 대한기계학회논문집B
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• 제21권11호
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• pp.1538-1551
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• 1997

Kinetic energy conservation for fixed and moving grids is examined in time-accurate finite element computation of fully unsteady inviscid flows. As numerical algorithms, fractional step method (FSM) and modified SIMPLE are used. To simulate the flow in moving grid system, arbitrary Lagrangian-Eulerian (ALE) method is adopted. In the present study, the energy conserving time integration rule for finite element algorithm is proposed and discussed schematically. It is shown that the discretization by Crank-Nicolson in time and Galerkin (central difference) in space must be used to ensure energy conservation. The developed code has been tested for a standing vortex in fixed or moving grid system, sloshing in a tank and propagation of a solitary wave, and has been shown to be a completely energy conserving algorithm.