• Title/Summary/Keyword: MAC Method Free Surface

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3차원 표면효과익의 자유표면 효과에 관한 수치연구

  • Gwak, Seung-Hyeon
    • Journal of Ocean Engineering and Technology
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    • v.12 no.2 s.28
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    • pp.79-86
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    • 1998
  • A three-dimensional WIG (Wing In Ground effect) moving above free surface is numerically studied by means of finite difference techniques. The air flow field around the WIG is analyzed by MAC (Marker & Cell) method, and interactions between WIG and the free surface are appeared as the variation of pressure distribution acting on the free surface. To analyze the wavemaking phenomena by those pressure distributions, the NS (Navier-Stokes) solver is employed in which nonlinearities of the free surface conditions can be included. Through the numerical simulation, Cp values and lift/drag ratio are carefully reviewed by changing the height/chord ratio. The section shape of model is NACA0012 with the span/chord ratio of 3.0. Through computational results, it is confirmed that the effect of free surface is small enough to treat it as a rigid wavy wall.

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Wave Generation with a Hydrofoil by More Efficient Free-Surface Boundary Condition (고효율 자유표면 경계조건에 의한 수중익 주위의 파도생성)

  • Kwag, S.H.
    • Journal of Korean Port Research
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    • v.12 no.1
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    • pp.87-93
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    • 1998
  • For the calculation of the free-surface elevation, a new finite difference scheme is studied where the third derivative term for the wave elevation is artificially added in the Eulerian expression of the free-surface boundary condition. The paper presents a comparative analysis with simulations performed by the classical MAC method. More schematic computations are carried out by changing the submergence-depth and angle-of-attack. The present study shows that this new method is very efficient for the simulation of free-surface elevation around the trailing edge.

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Numerical Study on Fluid Flows and Stirring in a Circular Cylinder Subjected to Circulatory Oscillation (회전요동하는 원통내의 유동 및 교반특성을 위한 수치해석적 연구)

  • Kim, Hyeun Mihn;Suh, Yong Kweon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.3
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    • pp.408-418
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    • 1999
  • Incompressible flow inside a circular cylinder Including periodically oscillating free surface waves was studied primarily by using a numerical method. We developed a finite difference scheme based on the MAC method applicable to three-dimensional free-surface flows, and applied it to the present flow model to study tho flow characteristics as well as the fluid stirring. To verify the validity of our scheme, we performed a simple experiment for flow visualization. We found that the numerical results show a reasonable agreement with the observed flow patterns.

Effects of Non-hydrostatic Pressure on Free Surface Environmental Flows (자유표면 환경유동에 대한 비정수압 효과)

  • Yoon, B.S.;Park, C.W.
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.8 no.3
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    • pp.116-121
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    • 2005
  • In the present paper, a new calculation algorithm far solving large scale environmental or geophysical flows with free surface is proposed where the non-hydrostatic pressure component is taken into consideration. Predictor-corrector fractional step approach with explicit, forward time marching scheme in the sigma coordinate system is employed. In order to validate the present calculation algorithm and to estimate the effects of non-hydrostatic pressure on resultant flow and free surface movements, example calculations are carried out for typical steady and unsteady flow problems. Present method can be applied to the meso-scale free surface flows with complex bottom topography where MAC-like 3-d hydrodynamic calculations are quite ineffective and uneconomic.

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Study on the Third-Order-Upwind-Difference(TOUD) for the Free-Surface Simulation (자유표면시뮬레이션의 TOUD 연구)

  • KWAG SEUNG-HYUN
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2004.11a
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    • pp.154-159
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    • 2004
  • A new finite difference scheme is studied fur the simulation of free surface, surface the third derivative tenn for the wave elevation is artificially added in the the free-surface boundary condition. This study presents a comparative analysis with simulations performed by using the classical MAC method. More systematic computations are carried out by changing the submergence depth and angle of attack. Through the numerical simulation, it is found that a new numerical method becomes more efficient for the reason that the free surface elevation is reasonably developed at tire rear of trailing edge.

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Lift/Drag Prediction of 3-Dimensional WIG Moving Above Free Surface

  • Kwag, Seung-Hyun
    • Journal of Mechanical Science and Technology
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    • v.15 no.3
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    • pp.384-391
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    • 2001
  • The aerodynamic effects of a 3-dimensional Wing in Ground Effect (WIG) which moves above the free surface has been numerically investigated via finite difference techniques. The air flow field around a WIG is analyzed by a Marker & Cell (MAC) based method, and the interactions between WIG and the free surface are studied by the pressure distributions on the free surface. Waves are generated by the surface pressure distribution, and a Navier-Stokes solver has been employed, to include the nonlinearities in the free surface conditions. The pressure values Cp and lift/drag ratio are reviewed by changing the height/chord ratio. In the present computations a NACA0012 airfoil with a span/chord ratio of 3.0 are treated. Through computational results, it is confirmed that the free surface can be treated as a rigid wavy wall.

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Computations of Free-Surface Flows by Use of Marker and Cell Method (MAC 방법을 이용한 자유표면 유동계산)

  • PARK Jong-Chun;SHIN Myung-Soo;VAN Suak-Ho;KIM Wu-Joan
    • 한국전산유체공학회:학술대회논문집
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    • 1995.10a
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    • pp.138-147
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    • 1995
  • The boundary conditions for the free-surface including the important meaning for both scientific and engineering purposes are described together with the numerical techniques to implement the conditions. Two kinds of numerical method based on MAC method are introduced. One is applied to the problem of 2D solitary wave propagation and the other is applied to the problem of 3D bow wave breaking.

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The visual Simulation of Fluid Flow with Free Surface in a Virtual Water Tank (가상수조에서 자유표면을 가진 유체흐름의 가시화시뮤레이션)

  • 김남형;김남국
    • Journal of Ocean Engineering and Technology
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    • v.14 no.3
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    • pp.35-40
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    • 2000
  • SMAC method is, one of the numerical simulation techniques, modified from the original MAC for the time-dependent variation of fluid flows. The Navier-Stokes equation for incompressible time-dependent viscous flow is applied and, also marker particles which move with the fluid are used. Two-dimensional numerical computations of fluid flow are carried out in a virtual water tank. This paper has shown very well the movements of marker particles using SMAC method.

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A FUNDAMENTAL STUDY ON THE NUMERICAL SIMULATION OF WAVE BREAKING PHENOMENON AROUND THE FORE-BODY OF SHIP (선수주위 쇄파현상의 수치시뮬레이션에 관한 기초연구)

  • Eom T.J.;Lee Y.-G.;Jeong K.-L.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.10a
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    • pp.195-199
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    • 2005
  • Wave breaking phenomenon near the fore body of a ship is numerically simulated. The ship advance with uniform velocity in calm water. For the simulation, incompressible Navier-Stokes equations and continuity equation are adopted as governing equations. The simulation is carried out in staggered variable mesh system with finite difference method. Marker and Cell(MAC) method and Marker-Density method are employed to track the free surface. Body boundary conditions are satisfied with the adoption of porosity method and no-slip condition on the hull surface. The ship model has a wedge type fore-body, and the computational domain is an appropriate region around the fore-body. The computation results are compared with some experimental results. Also the difference of the free surface tracking methods are discussed.

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Numeric Analysis of 2-Dimensional Nonlinear Viscous Free-Surface Wave Problems (점성을 고려한 2차원 비선형 자유표면파 문제의 수치해석)

  • Y.H. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.30 no.2
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    • pp.98-111
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    • 1993
  • Two-dimensional nonlinear free-surface wave problems are analyzed with consideration of viscosity. Navier-Stokes equation and continuity equation are solved by the application of Finite Analytic Method, and MAC scheme is used far the treatment of free surface. Surface tension effect is also considered and laminar flow is assumed. The free-surface waves in shallow water, the flows around a vortex-pair with free surface and the wave ahead of a rectangular body are simulated to test the present numerical scheme. In the shallow water problem, viscous effect due to the friction on the bottom is observed. In the second problem, the approach of a vortex-pair to the free surface is simulated to examine the interaction of vortex-pair with the free surface. In the third problem, the wave ahead of a semi-infinite floating body is simulated.

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