• 제목/요약/키워드: Non-linear free-surface motions

검색결과 12건 처리시간 0.022초

Free Surface Oscillation in Sloshing Problem Predicted with ALE Method

  • Ushijima Satoru
    • 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.

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입자법을 이용한 비선형성 자유표면 유동의 수치 시뮬레이션 (Numerical Simulation of Non-linear Free-surface Motions Using Moving Particle Semi-implicit(MPS) Method)

  • 이병혁;정성준;류민철;김용수;김영훈;박종천
    • 한국해양공학회지
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    • 제21권6호
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    • pp.53-58
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    • 2007
  • A particle method, recognized as one of gridless methods, has been developed to investigate non-linear free-surface motions interacting with structures. This method is more feasible and effective than conventional grid methods for solving flow fieldswith complicated boundary shapes. The method consists of particle interaction models representing pressure gradient, diffusion, incompressibility, and the free-surface boundary conditions without grids. In the present study, broken dam problems with various viscosity values are simulated to validate the developed method.

Influence of viscous effects on numerical prediction of motions of SWATH vessels in waves

  • Brizzolara, Stefano;Bonfiglio, Luca;Medeiros, Joao Seixas De
    • Ocean Systems Engineering
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    • 제3권3호
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    • pp.219-236
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    • 2013
  • The accurate prediction of motion in waves of a marine vehicle is essential to assess the maximum sea state vs. operational requirements. This is particularly true for small crafts, such as Autonomous Surface Vessels (ASV). Two different numerical methods to predict motions of a SWATH-ASV are considered: an inviscid strip theory initially developed at MIT for catamarans and then adapted for SWATHs and new a hybrid strip theory, based on the numerical solution of the radiation forces by an unsteady viscous, non-linear free surface flow solver. Motion predictions obtained by the viscous flow method are critically discussed against those obtained by potential flow strip theory. Effects of viscosity are analyzed by comparison of sectional added mass and damping calculated at different frequencies and for different sections, RAOs and motions response in irregular waves at zero speed. Some relevant conclusions can be drawn from this study: influence of viscosity is definitely non negligible for SWATH vessels like the one presented: amplitude of the pitch and heave motions predicted at the resonance frequency differ of 20% respectively and 50%; in this respect, the hybrid method with fully non-linear, viscous free surface calculation of the radiation forces turns out to be a very valuable tool to improve the accuracy of traditional strip theories, without the burden of long computational times requested by fully viscous time domain three dimensional simulations.

입자법을 이용한 댐 붕괴의 수치 시뮬레이션 (NUMERICAL SIMULATION OF DAM-BROKEN PROBLEMS USING A PARTICLE METHOD)

  • 이병혁;정성준;김영훈;박종천
    • 한국전산유체공학회지
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    • 제13권1호
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    • pp.28-34
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    • 2008
  • A particle method recognized as one of the gridless methods has been developed to investigate the nonlinear free-surface motions interacting to the structures. The method is more feasible and effective than convectional grid methods for solving the non-linear free-surface motion with complicated boundary shapes. The right-handed side of the governing equations for incompressible fluid, which includes gradient, viscous and external force terms, can be replaced by the particle interaction models. In the present study, the developed method is applied to the dam-broken problem on dried- and wet-floor and its adequacy will be discussed by the comparison with the experimental results.

입자법을 이용한 댐 붕괴의 수치 시뮬레이션 (NUMERICAL SIMULATION OF DAM-BROKEN PROBLEMS USING A PARTICLE METHOD)

  • 박종천;이병혁;정성준
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2007년도 추계 학술대회논문집
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    • pp.258-263
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    • 2007
  • A particle method recognized as one of the gridless methods has been developed to investigate the nonlinear free-surface motions interacting to the structures. The method is more feasible and effective than convectional grid methods for solving the non-linear free-surface motion with complicated boundary shapes. The right-handed side of the governing equations for incompressible fluid, which includes gradient, viscous and external force terms, can be replaced by the particle interaction models. In the present study, the developed method is applied to the dam-broken problem on dried- and wet-floor and its adequacy will be discussed by the comparison with the experimental results.

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Occurrence mechanism of recent large earthquake ground motions at nuclear power plant sites in Japan under soil-structure interaction

  • Kamagata, Shuichi;Takeqaki, Izuru
    • Earthquakes and Structures
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    • 제4권5호
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    • pp.557-585
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    • 2013
  • The recent huge earthquake ground motion records in Japan result in the reconsideration of seismic design forces for nuclear power stations from the view point of seismological research. In addition, the seismic design force should be defined also from the view point of structural engineering. In this paper it is shown that one of the occurrence mechanisms of such large acceleration in recent seismic records (recorded in or near massive structures and not free-field ground motions) is due to the interaction between a massive building and its surrounding soil which induces amplification of local mode in the surface soil. Furthermore on-site investigation after earthquakes in the nuclear power stations reveals some damages of soil around the building (cracks, settlement and sand boiling). The influence of plastic behavior of soil is investigated in the context of interaction between the structure and the surrounding soil. Moreover the amplification property of the surface soil is investigated from the seismic records of the Suruga-gulf earthquake in 2009 and the 2011 off the Pacific coast of Tohoku earthquake in 2011. Two methods are introduced for the analysis of the non-stationary process of ground motions. It is shown that the non-stationary Fourier spectra can detect the temporal change of frequency contents of ground motions and the displacement profile integrated from its acceleration profile is useful to evaluate the seismic behavior of the building and the surrounding soil.

받음각을 갖는 평판의 유체 충격 시뮬레이션 (Numerical Simulation for Fluid Impact Loads by Flat Plate with Incident Angles)

  • 이병혁;정성준;류민철;김용수;박종천
    • 대한조선학회논문집
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    • 제45권1호
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    • pp.1-9
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    • 2008
  • The free-surface motions interacting with structures are investigated numerically using the Moving Particle Semi-implicit (MPS) method proposed by Koshizuka et al. (1996) for solving incompressible flow. In the method, Lagrangian moving particles are used instead of Eulerian approach using grid system. Therefore the terms of time derivatives in Navier-Stokes equation can be directly calculated without any numerical diffusion or instabilities due to the fully Lagrangian treatment of fluid particles and topological failure never occur. The MPS method is applied to the numerical study on the fluid impact loads for wet-drop tests in a LNG tank, and the results are compared with experimental ones.

원호운동 필렛 엔드밀과 Z-맵 벡터의 교점 계산 (Calculation of Intersection between Z-map Vectors and Circularly Moving Filleted-end Mills)

  • 맹승렬;백낙훈;신성용;최병규
    • 한국CDE학회논문집
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    • 제8권4호
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    • pp.278-288
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    • 2003
  • Presented in this paper is a numerical method for calculating the intersection points between Z-map vectors and the tool swept surface for circularly moving filleted-end mills. In numerically controlled(NC) machining simulation for large moulds and dies, a workpiece is frequently approximated as a set of z-axis aligned vectors, called Z-map vectors, and then the machining processes can be simulated through updating the Z-map with the intersection points. Circular motions are typically used for machining the free-form surfaces. For fast computation, we express each of intersection points with a single-variable non-linear equation and calculate the candidate interval in which the unique solution exists. Then, we prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the nonlinear equation within a given precision. Experimental results are given for the case of a TV monitor and the hood of a car.

입자법에 의한 파랑중 2차원 부유체 운동 시뮬레이션 (Numerical Simulation of Two-dimensional Floating Body Motion in Waves Using Particle Method)

  • 정성준;박종천;이병혁;류민철;김용수
    • 한국해양공학회지
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    • 제22권2호
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    • pp.20-27
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    • 2008
  • A moon-pool is a vertical well in a floating barge, drilling ship, or offshore support vessel. In this study, numerical simulation of two-dimensional moon-pool flaw coupled with a ship's motion in waves is carried out using a particle method, the so-called MPS method. The particle method, which is recognized as one of the gridless methods, was developed to investigate nonlinear free-surface motions interacting with structures. The method is more feasible and effective than convectional grid methods in order to solve a flaw field with complicated boundary shapes.

파랑 충격하중에 관한 3차원 입자법 수치모사 (Numerical Simulation of Tsunami Impact Load Using 3-Dimensional Particle Method)

  • 김영훈;정성준;이병혁;황성철;박종천
    • 한국해양공학회지
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    • 제21권6호
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    • pp.42-46
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    • 2007
  • The impact of a single wave generated by a dam break with a tall structure is modeled with a three-dimensional version of the Moving particle semi-implicit (MPS) method. The particle method is more feasible and effective than methods based on grid connection problems involving violent free surface motions. In the present study, the Tsunami impact load and the change of longitudinal velocity component around the structure, which are obtained from the numerical simulation, are compared to those from experiments.