• Title/Summary/Keyword: semi-Lagrangian

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Characteristic Analysis of Nonlinear Sloshing in Baffled Tank (격막 설치에 따른 비선형 슬로싱 특성 연구)

  • Lee, Hong-Woo;Cho, Jin-Rae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.11 s.242
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    • pp.1455-1462
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    • 2005
  • In this paper, we intend to introduce a nonlinear finite element method based on the fully nonlinear potential flow theory in order to simulate the large amplitude sloshing flow in two-dimensional baffled tank subject to horizontally forced excitation. The free surface is tracked by a direct time differentiation scheme with the four-step predictor-corrector time integration method. The flow velocity is accurately recovered from the velocity potential by second-order least square method. In order to maintain the finite element mesh regularity and total mass, the semi-Lagrangian surface tracking method with area conservation is applied. According to the numerical formulae, we perform the parametric experiments by varying the installation height and the opening width of baffles, in order to examine the effects of baffle on the nonlinear liquid sloshing. From the numerical results, the hydrodynamic characteristics of the large amplitude sloshing are investigated.

SOLVING A CLASS OF GENERALIZED SEMI-INFINITE PROGRAMMING VIA AUGMENTED LAGRANGIANS

  • Zhang, Haiyan;Liu, Fang;Wang, Changyu
    • Journal of applied mathematics & informatics
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    • v.27 no.1_2
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    • pp.365-374
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    • 2009
  • Under certain conditions, we use augmented Lagrangians to transform a class of generalized semi-infinite min-max problems into common semi-infinite min-max problems, with the same set of local and global solutions. We give two conditions for the transformation. One is a necessary and sufficient condition, the other is a sufficient condition which can be verified easily in practice. From the transformation, we obtain a new first-order optimality condition for this class of generalized semi-infinite min-max problems.

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Improved Weighted Integral Method and Application to Analysis of Semi-infinite Domain (개선된 가중적분법과 반무한 영역의 해석)

  • 노혁천;최창근
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2002.04a
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    • pp.369-376
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    • 2002
  • The stochastic analysis of semi-infinite domain is presented using the weighted integral method, which is improved to include the higher order terms in expanding the displacement vector. To improve the weighted integral method, the Lagrangian remainder is taken into account in the expansion of the status variable with respect to the mean value of the random variables. In the resulting formulae only the 'proportionality coefficients' are introduced in the resulting equation, therefore no additional computation time and memory requirement is needed. The equations are applied in analyzing the semi-infinite domain. The results obtained by the improved weighted integral method are reasonable and are in good agreement with those of the Monte Carlo simulation. To model the semi-infinite domain, the Bettess's infinite element is adopted, where the theoretical decomposition of the strain-displacement matrix to calculate the deviatoric stiffness of the semi-infinite domains is introduced. The calculated value of mean and the covariance of the displacement are revealed to be larger than those given by the finite domain assumptions which is thought to be rational and should be considered in the design of structures on semi-infinite domains.

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Flood Impact Pressure Analysis of Vertical Wall Structures using PLIC-VOF Method with Lagrangian Advection Algorithm

  • Phan, Hoang-Nam;Lee, Jee-Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.6
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    • pp.675-682
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    • 2010
  • The flood impact pressure acting on a vertical wall resulting from a dam-breaking problem is simulated using a navier-Stokes(N-S) solver. The N-S solver uses Eulerian Finite Volume Method(FVM) along with Volume Of Fluid(VOF) method for 2-D incompressible free surface flows. A Split Lagrangian Advection(SLA) scheme for VOF method is implemented in this paper. The SLA scheme is developed based on an algorithm of Piecewise Linear Interface Calculation(PLIC). The coupling between the continuity and momentum equations is affected by using a well-known Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm. Several two-dimensional numerical simulations of the dam-breaking problem are presented to validate the accuracy and demonstrate the capability of the present algorithm. The significance of the time step and grid resolution are also discussed. The computational results are compared with experimental data and with computations by other numerical methods. The results showed a favorable agreement of water impact pressure as well as the global fluid motion.

Hydrodynamic characteristics of a fixed semi-submersible platform interacting with incident waves by fully nonlinear method

  • Zhang, Zi-Lin;Yuan, Hong-Tao;Sun, Shi-Li;Ren, Hui-Long
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.13 no.1
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    • pp.526-544
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    • 2021
  • Based on the potential flow theory, a fully nonlinear numerical procedure is developed with boundary element method to analyze the interaction between a fixed semi-submersible platform and incident waves in open water. The incident wave is separated from the scattered wave under fully nonlinear boundary conditions. The mixed Euler-Lagrangian method is used to capture the position of the disturbed wave surface in local coordinate systems. The wave forces exerted on an inverted conical frustum are used to ensure the accuracy of the present method and good agreements with published results are obtained. The hydrodynamic characteristics of the semi-submersible platform interacting with regular waves are analyzed. Pressure distribution with time and space, tension and compression of the platform under wave action are investigated. 3D behaviors of wave run-ups are predicted. Strong nonlinear phenomena such as wave upwelling and wave interference are observed and analyzed.

Towards development of a reliable fully-Lagrangian MPS-based FSI solver for simulation of 2D hydroelastic slamming

  • Khayyer, Abbas;Gotoh, Hitoshi;Falahaty, Hosein;Shimizu, Yuma;Nishijima, Yusuke
    • Ocean Systems Engineering
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    • v.7 no.3
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    • pp.299-318
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    • 2017
  • The paper aims at illustrating several key issues and ongoing efforts for development of a reliable fully-Lagrangian particle-based solver for simulation of hydroelastic slamming. Fluid model is founded on the solution of Navier-Stokes along with continuity equations via an enhanced version of a projection-based particle method, namely, Moving Particle Semi-implicit (MPS) method. The fluid model is carefully coupled with a structure model on the basis of conservation of linear and angular momenta for an elastic solid. The developed coupled FSI (Fluid-Structure Interaction) solver is applied to simulations of high velocity impact of an elastic aluminum wedge and hydroelastic slammings of marine panels. Validations are made both qualitatively and quantitatively in terms of reproduced pressure as well as structure deformation. Several remaining challenges as well as important key issues are highlighted. At last, a recently developed multi-scale MPS method is incorporated in the developed FSI solver towards enhancement of its adaptivity.

NUMERICAL ANALYSIS FOR THE SHALLOW WATER EQUATIONS ON THE SPHERE BY CIP METHOD (CIP법을 이용한 구 좌표계에서의 천수 방정식 해석)

  • Yoon, Seong-Young;Kim, Soo-Youn;Kim, Hyun-Chul
    • Journal of computational fluids engineering
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    • v.10 no.2
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    • pp.7-14
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    • 2005
  • In this study, the shallow water equations on the sphere is simulated by the proposed method which has high spatial resolution and is based on the CIP(Cubic Interpolated Pseudoparticle) method. The governing equations are approximated on the longitude-latitudinal coordinate system. To avoid the problems resulting from the convergence of the meridians toward high-latitude and singularities on the poles, the semi-Lagrangian and finite volume method are employed. in addition, the CIP method is employed to solve the advection equations and is extended to apply on the equations in the polar coordinate system. The mathematical formulation and numerical results are also described. To verify of the efficiency, accuracy and capability of proposed algorithm, the standard test cases proposed bv Williamson et. al are simulated and the results are compared with other results. As a result, it is found that the present scheme gives a good properties in preserving shapes of solution and settles the pole problems in solving the shallow water equations on the sphere.

Failure simulation of ice beam using a fully Lagrangian particle method

  • Ren, Di;Park, Jong-Chun;Hwang, Sung-Chul;Jeong, Seong-Yeob;Kim, Hyun-Soo
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.11 no.2
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    • pp.639-647
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    • 2019
  • A realistic numerical simulation technology using a Lagrangian Fluid-Structure Interaction (FSI) model was combined with a fracture algorithm to predict the fluid-ice-structure interaction. The failure of ice was modeled as the tensile fracture of elastic material by applying a novel FSI model based on the Moving Particle Semi-implicit (MPS) method. To verify the developed fracture algorithm, a series of numerical simulations for 3-point bending tests with an ice beam were performed and compared with the experiments carried out in an ice room. For application of the developed FSI model, a dropping water droplet hitting a cantilever ice beam was simulated with and without the fracture algorithm. The simulation showed that the effects of fracture which can occur in the process of a FSI simulation can be studied.

Applications of Three-Dimensional Multiphase Flow Simulations for Prediction of Wave Impact Pressure (유체충격력 예측을 위한 3차원 다상류 시뮬레이션의 응용)

  • Jeong, Se-Min;Hwang, Sung-Chul;Park, Jong-Chun
    • Journal of Ocean Engineering and Technology
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    • v.27 no.2
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    • pp.39-46
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    • 2013
  • In this study, the impact loads on tank walls by sloshing phenomena and on a tall structure in a three-dimensional rectangular tank were predicted using multiphase flow simulations. The solver was based on the CIP/CCUP (Constraint interpolation CIP/CIP combined unified procedure) method, and the THINC-WLIC (Tangent hyperbola for interface capturing-weighted line interface calculation) scheme was used to capture the air-water interface. For the convection terms of the Navier-Stokes equations, the USCIP (Unsplit semi-lagrangian CIP) method was adopted. The results of simulations were compared with those of experiments. Overall, the comparisons were reasonably good.