• Title/Summary/Keyword: 자유표면 유동

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Second Order Model for Free Surface Convection (자유표면유동을 위한 이차원 모델개발)

  • Kim Seong-O.
    • Journal of computational fluids engineering
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    • v.2 no.2
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    • pp.73-79
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    • 1997
  • VOF 방법에 의한 자유표면 유동계산의 정확성을 개선하기 위해 이차정도 모델을 개발하였다. 개발된 이차원 모델의 정확성을 비교하기 위하여 여러 가지 크기의 원형 및 Solitary wave형상의 자유표면 유동을 통하여 기존에 개발된 두 가지의 일차정도 모델과 비교하였다. 비교결과 반경이 큰 원과 같이 곡률이 작은 형상의 경우에는 일차정도 모델도 비교적 정확한 결과를 보여주고 있으나 작은 반경의 원형이나 Solitary wave와 같이 곡률이 큰 형상의 경우 일차정도 모델은 많은 오차를 보여주는 반면에 이차정도 모델은 어느 경우에나 매우 정확한 결과를 보여준다.

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Numerical Calculation of the free-Surface Flows around a Submerged Body (잠수체 주위 자유표면 유동의 수치계산)

  • 김용직;하영록;홍사영
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.2
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    • pp.11-20
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    • 2003
  • In this paper, the high-order spectral/boundary-element method is developed to calculate the 3-dimensional water waves generated by a submerged body. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated Tn time-domain. Three-dimensional free-surface flows generated by a submerged sphere which is moving under the free-surface are calculated. Through example calculations, nonlinear effects on free-surface profiles and hydrodynamic forces are shown. Comparisons with others' results show good agreements.

A method for incompressible free surface flow including surface tension using CSF model (CSF 모델을 이용한 자유표면 유동 해석)

  • Hong I. C.;Baek J. H.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.10a
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    • pp.15-18
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    • 2004
  • A numerical method for simulating two-phase flows including surface force is presented. The method is based on fractional step method of finite volume formulation and the interface is tracked with PLIC VOF method. In the CSF model, as color function, f, representing the location of interface varies steeply in the interface region, we need to use smoothed function f to get accurate unit normal and the curvature. Peskin kernel is used to get smoothed function f. A spherical drop in static equilibrium and three-dimensional merging of gas bubble are tested, resulting in the validation of this method

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Study on High Accurate Schemes for Simulation of Free-surface Flow (자유표면 유동 시뮬레이션을 위한 고정확도 수치도식의 검토)

  • Park, Jong-Chun;Lee, Byoung-Hyuk;Kim, Jeung-Hu
    • Journal of Ocean Engineering and Technology
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    • v.20 no.4 s.71
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    • pp.31-36
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    • 2006
  • Numerical schemes for spacing and time are tested to accurately simulate the wave propagation. The tested numerical schemesinclude 2nd-order central differencing, l-order upwind scheme, 2nd-order Leith scheme, 3rd-order MUSCLE, QUICK and QUICKEST schemes in spacing and the Euler and 4th-order Runge-Kutta(R-K) schemes in time. It is seen that more accurate results are expected when the higher-order schemes, especially the schemes combined with a TVD control limiter, are used for solving the wave equation. The 3rd-order upwind scheme with limiter and the 4th-order R-K scheme in tim£ are finally applied to the wave-making simulation in a digital wave tank.

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

  • Lee, Byung-Hyuk;Jeong, Seong-Jun;Ryu, Min-Cheol;Kim, Yong-Soo;Kim, Young-Hun;Park, Jong-Chun
    • Journal of Ocean Engineering and Technology
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    • v.21 no.6
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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.

Time-Domain Simulation of Nonlinear Free-Surface Flows around a Two-Dimensional Hydrofoil (2차원 수중익주위 비선형 자유표면유동의 시간영역 시뮬레이션)

  • Yong-J. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.31 no.2
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    • pp.45-56
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    • 1994
  • A computationally efficient numerical method based on potential flow is developed for time-domain simulation of the nonlinear free-surface flows around a 2-dimensional hydrofoil. This numerical method, namely, spectral/boundary-element method, is a mixed one of the high-order spectral method and the boundary-element method in time-domain. The high-order spectral method is used to calculate the nonlinear evolution of free-surface, and the boundary-element method is used to calculate the effects of the hydrofoil and the shed vortex. As application examples, nonlinear free-surface flows around a 2-dimensional hydrofoil which starts from the rest and translates near the free-surface with or without harmonic oscillations are calculated. Nonlinear/unsteady results of free-surface waves and hydrodynamic farces are shown and discussed. Particularly, the results of steady-state which are obtained as a special case of the present unsteady solution are compared with others' calculated and experimental results, and good agreements are observed.

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Two Dimensional Numerical Simulation of Liquid Sloshing (액체 슬라상에 관한 2차원 수치 시뮬레이션)

  • Kang, Sin Young
    • Journal of Ocean Engineering and Technology
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    • v.2 no.1
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    • pp.78-82
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    • 1988
  • 자유표면 유동을 시뮬레이션할 수 있는 수치 알고리듬 중 가장 최근에 개발된 volume of fluid (VOF) 방법을 이용하여 뚜껑이 닫힌 사각 컨테이너 속의 슬라싱을 시뮬레이션 하였다. 그 결과 유동이 작은 경우에는 알고리듬이 불안정하게 되어 장기간 시뮬레이션을 어렵게 하는 문제점이 발견되었다. 이 문제점을 해결하기 위해 VOF 알고리듬이 불안정하게 되어 장기간 시뮬레이션을 어렵게하는 문제점이 발견되었다. 이 문제점을 해결하기 위해 VOF 알고리듬 중 유량이동 알고리듬을 수정하여 원래의 알고리듬으로 시뮬레이션한 결과와 비교 분석하였다

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A Study of Numerical Method for Analysis of the 3-Dimensional Nonlinear Wave-Making Problems (3차원 비선형 조파문제 해석을 위한 수치해법 연구)

  • Ha, Y.R.;An, N.H.
    • Journal of Power System Engineering
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    • v.16 no.5
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    • pp.40-46
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    • 2012
  • For free surface flow problem, a high-order spectral/boundary element method is adapted as an efficient numerical tool. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated and hydrodynamic forces also can be calculated in time domain. In this method, the velocity potential is expressed as the sum of surface potential and body potential. Then, surface potential is solved by using the high-order spectral method and body potential is solved by using the high-order boundary element method. Using the combination of these two methods, the free surface flow problems of a submerged moving body are solved in time domain. In the present study, lifting surface theory is added to the former work to include effects of lift force. Therefore, a new formulation for the basic mathematical theory is introduced to contain the lift body in calculation.

Calculation of Nonlinear Interactions between Hydrofoil and Free-Surface by the High-Order Spectral/Boundary-Integral Method (고차 스펙트럴 / 경계적분법에 의한 수중익과 자유표면의 비선형 상호작용 계산)

  • 김용직;하영록
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.39 no.1
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    • pp.27-32
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    • 2003
  • Under the assumption of potential flow, free-surface flow around a hydrofoil is calculated by the high-order spectra1!boundary-integral method, This method is one of the most efficient numerical methods by which the nonlinear interactions between hydrofoil and free-surface can be simulated in time-domain. In this method. the wave potential which represents the nonlinear evolution of free-surface is solved by the high-order spectral method and the body potential which provides the effects of hydrofoil and shed vortex is solved by the boundary-integral method. The calculated free-surface profiles which are generated by a uniformly translating hydrofoil are compared with other experimental results. And they show relatively good agreements each other. As another example, free-surface flow generated by a heaving and translating hydrofoil is calculated and discussed.

Development of WMLS-based Particle Simulation Method for Solving Free-Surface Flow (자유표면 유동해석을 위한 WMLS 기반 입자법 기술 개발)

  • Nam, Jung-Woo;Park, Jong-Chun;Park, Ji-In;Hwang, Sung-Chul;Heo, Jae-Kyung;Jeong, Se-Min
    • Journal of Ocean Engineering and Technology
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    • v.28 no.2
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    • pp.93-101
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    • 2014
  • In general, particle simulation methods such as the MPS(Moving Particle Simulation) or SPH(Smoothed Particle Hydrodynamics) methods have some serious drawbacks for pressure solutions. The pressure field shows spurious high fluctuations both temporally and spatially. It is well known that pressure fluctuation primarily occurs because of the numerical approximation of the partial differential operators. The MPS and SPH methods employ a pre-defined kernel function in the approximation of the gradient and Laplacian operators. Because this kernel function is constructed artificially, an accurate solution cannot be guaranteed, especially when the distribution of particles is irregular. In this paper, we propose a particle simulation method based on the moving least-square technique for solving the partial differential operators using a Taylor-series expansion. The developed method was applied to the hydro-static pressure and dam-broken problems to validate it.