• Explosives and Blasting
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• v.37 no.3
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• pp.13-24
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• 2019

This paper was prepared to investigate the behavior of fragments in underwater torpedo explosion beneath a frigate or surface ship by using an explicit finite element analysis. In this study, a fluid-structure interaction (FSI) methodology, called the multi-material arbitrary Lagrangian-Eulerian (MM-ALE) approach in LS-DYNA, was employed to obtain the responses of the torpedo fragments and frigate hull to the explosion. The Euler models for the analysis were comprised of air, water, and explosive, while the Lagrange models consisted of the fragment and the hull. The focus of this modeling was to examine whether a worst-case fragment could penetrate the frigate hull located close (4.5 m) to the exploding torpedo. The simulation was performed in two separate steps. At first, with the assumption that the expanding skin of the torpedo had been torn apart by consuming 30% of the explosive energy, the initial velocity of the worst-case fragment was sought based on a well-known experimental result concerning the fragment velocity in underwater bomb explosion. Then, the terminal velocity of the worst-case fragment that is expected to occur before the fragment hit the frigate hull was sought in the second step. Under the given conditions, the possible initial velocities of the worst-case fragment were found to be very fast (400 and 1000 m/s). But, the velocity difference between the fragment and the hull was merely 4 m/s at the instant of collision. This result was likely to be due to both the tremendous drag force exerted by the water and the non-failure condition given to the frigate hull. Anyway, at least under the given conditions, it is thought that the worst-case fragment seldom penetrate the frigate hull because there is no significant velocity difference between them.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.286-287
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• 2008

The determination of roll speeds in continuous rolling system is an important factor along with the design of roll profile and roll gap. The tensile force on the workpiece induces reduced cross section area and the compressive force induces wrinkles. To determine the optimal roll speeds of current rough rolling system for wire rod, FE analysis was performed. We could predict the workpiece shape and the stress level more precisely by considering the elasto-plastic behavior of workpiece. Also the efficient analysis methodology is presented to reduce the calculation time by combining the ALE and lagrangian method.

• BMB Reports
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• v.39 no.3
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• pp.292-296
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• 2006

DNA sequencing has resulted in an abundance of data on DNA sequences for various species. Hence, the characterization and comparison of sequences become more important but still difficult tasks. In this paper, we first give a 2-D ladderlike graphical representation for the characteristic sequences of a DNA sequence, and then construct a 3-component vector, in which the normalized ALE-indices extracted from such three 2-D graphs via D/D matrices are individual components, to characterize the DNA sequence. The examination of similarities/dissimilarities among sequences of the $\beta$-globin genes of different species illustrates the utility of the approach.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.141-150
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• 2002

Numerical simulations based on the ALE finite element method are carried out to examine the aerodynamics of an oscillating circular cylinder when the separated shear flows around the cylinder are stimulated by periodic jet excitation with a shear layer instability frequency. The excitation is applied to the flows from two points on the cylinder surface. The numerical results showed that the excitation with a shear layer instability frequency can reduce the negative damping and thereby stabilize the aerodynamics of the oscillating cylinder. The change of the lift phase seems important in stabilizing the cylinder aerodynamics. The change of lift phase is caused by the merger of the vortices induced by the periodic excitation with a shear layer instability frequency, and the vortex merging comes from the high growth rate, the rapid increase of wave number and decrease of phase velocity for the periodic excitation in the separated shear flows.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.2
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• pp.137-152
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• 2016

This paper studied the dynamic response of a new gasbag-type floating bridge under the effect of a moving load. The arbitrary Lagrangian-Eulerian (ALE) method was used to simulate the movement of seawater and air, and the penalty-based method was used to study the coupling between gasbags and fluid. A three-dimensional finite element model of the floating bridge was established, and the numerical model was verified by comparing with the experimental results. In order to prevent resonance, the natural frequencies and flexural mode shapes were analyzed. Based on the initial state analysis, the dynamic responses of the floating bridge subjected to different moving loads were investigated. Vertical displacements and radial deformations of gasbags under different loads were compared, and principal stress distributions of gasbags were researched while driving. The hinge forces between adjacent modules were calculated to ensure the connection strength. Besides, the floating bridge under wave impacting was analyzed. Those results can provide references for the analysis and design of this new floating bridge.

• Structural Engineering and Mechanics
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• v.13 no.6
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• pp.653-670
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• 2002

In order to ensure the structural dynamic stability of moving liquid-storage containers, the flow motion of interior liquid should be appropriately suppressed by means of mechanical devices such as the disc-type elastic baffle. In practice, the design of a suitable baffle requires a priori the parametric dynamic characteristics of storage containers, with respect to the design parameters of baffle, such as the installation location and inner-hole size, the baffle number, and so on. In this paper, we intend to investigate the parametric effect of the baffle parameters on the transient dynamic behavior of a cylindrical fuel-storage tank in an abrupt vertical acceleration motion. For this goal, we employ the ALE (arbitrary Lagrangian-Eulerian) kinematic description method incorporated with the finite element method.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.180.2-180
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• 2001

In the hot rolling process, the RF AGC (Roll Force Auto Gauge Control) is used to control the roll gap to reduce the variation of rolling force caused by the roll eccentricity and the variation of material thickness. However the effect of the roll eccentricity cannot be distinguished. To eliminate the effect of the roll eccentricity, the roll eccentricity estimation is needed to supplement some drawbacks of RF AGC. In this paper, an ALE(Adaptive Line Enhancer) that extracts the rolling force variation due to the roll eccentricity is suggested. We also provide an algorithm that enhances the convergence time of roll eccentricity estimation. The performance improvement of the Suggested algorithm is shown via simulations.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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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.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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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.

• Journal of computational fluids engineering
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• v.4 no.2
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• pp.39-46
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• 1999

The FVM(Finite Volume Method) have been used mainly for the flow analyses in the piston-cylinder. The objective of the present study is to analyze numerically the piston-driven intake flows using the FEM(Finite Element Method). The FEM algorithm used in this study is 4-step time-splitting method which requires much less execution time and computer storage than the velocity-pressure integrated method and the penalty method. And the explicit Lax-Wendroff scheme is applied to nonlinear convective term in the momentum equations to prevent checkerboard pressure oscillations. Also, the ALE(arbitrary Lagrangian Eulerian) method is adopted for the moving grids. The calculated results show good agreement in comparison with those by the FVM and the experimental results by the LDA.