• 한국구조물진단유지관리공학회 논문집
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• 제21권6호
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• pp.59-66
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• 2017

유체 저장 구조물의 경우 지진 시 유체의 출렁임에 의하여 구조물에 동수압이 작용한다. 이 때, 유체의 동수압은 지진의 강도뿐만 아니라 유체 자유수면의 출렁임 높이(sloshing height)에 의해서도 변화한다. 이러한 하중의 변화에 영향을 미치는 인자로는 지진파의 형상, 최대지진강도, 유체 저장 구조물의 크기, 구조물의 폭, 유체의 높이 등이 있는데, 본 논문에서는 지진파의 형상과 유체 자유수면의 출렁임 형상의 상관관계를 규명하고자 하였다. 이를 위하여 구조물의 폭이 500 mm인 수조에 실지진파를 적용시켜 유체 자유수면의 출렁임 높이를 측정하고, 수치해석을 통하여 실험과 해석의 유사성을 검증하였다. 또한, 실험과 해석의 비교를 통하여 검증된 구조해석 기법을 적용하여 인공지진파의 형상을 다양하게 변화시키면서 유체 자유수면의 출렁임 형상의 변화를 측정하고, 인공지진파의 형상이 유체 자유수면의 출렁임 형상에 미치는 영향을 분석하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제24권5호
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• pp.126-134
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• 2020

유체 저장 구조물은 지진 시 유체의 출렁임에 의해 동수압이 발생한다. 이 때, 유체의 동수압은 지진의 강도뿐만 아니라 유체 자유수면의 출렁임 높이(sloshing height)에 의해서도 변화한다. 이러한 하중 변화에 영향을 미치는 인자로는 지진파의 형상, 최대지진강도, 유체 저장구조물의 크기, 구조물의 폭, 유체의 높이 등이 있으며, 본 연구에서는 유체높이와 구조물 폭의 비가 유체의 출렁임 특성에 미치는 영향을 규명하고자 한다. 이를 위하여 구조물의 폭이 500mm인 수조에 구조물의 전체 높이 대비 50%인 200mm와 35%인 140mm의 유체를 담아 실지진파를 적용시켜 유체 자유수면의 출렁임 높이를 측정하였다. 또한 수치해석기법 중 하나인 SPH기법을 통하여 실험과 해석의 유사성을 검증하였다. 실험과 해석의 비교를 통하여 유체의 자유 수면이 유사한 형상을 나타냄을 확인하였으며, 이를 바탕으로 SPH기법을 적용하여 유체높이와 구조물 폭의 비를 다양하게 변화시키면서 유체 자유수면의 출렁임 형상을 분석하였다. 이상의 결과를 바탕으로 지진시 유체 자유수면의 최대 높이 및 최소높이를 예측할 수 있는 식을 제안하였으며, 제안식에 의해 예측된 유체 자유수면의 최대 높이 및 최소 높이의 오차는 최대 3% 이내임을 확인하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.48-57
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• 1999

This paper deals with the numerical simulation of the behavior of single bubble rising near the free surface. Volume fraction of fluid (VOF) method with continuum surface force (CSF) model, the well known method for two phase flow simulation is adopted. A bubble of spherical shape positioned beneath the free surface is assumed at the initial stage. The difference according to the fluid properties of surrounding medium is examined. Simulation results are depicted and explained with the time history of bubble shape, velocity field and vorticity distribution.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.99-102
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• 2002

The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank The SOLA-VOF (Volume of fluid) method uses a fixed mesh for calculating the motion of flow and the free-surface. This Eulerian approach enables the VOF method to use only a small amount of computer memory for simulating sloshing problems with complicated free-surface contours. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the locating of the free-surface filling any some fraction of cells with fluid. Using SOLA-VOF method, the study describes visualization about simulation of the sloshing of flows and damping effect by baffle. Translation and pitching motion of the forms have been investigated The time-dependent changes of free-surface height are used for visualization subject to several conditions such as fluid height horizontal acceleration, sinusoidal motion, and viscosity. The free-surface heights were used for comparing wall-force, which is caused by sloshing of flows. Baffle was Installed to reduce the force on the wall by sloshing of flows. Damping effects was extensively expressed under the conditions such as baffle shape and position.

• 한국전산유체공학회지
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• 제4권2호
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• pp.31-38
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• 1999

Numerical analysis is conducted on the deformation of free surface of magnetic fluid. Steady magnetic fields are induced by a circular current loop. Governing equations of magnetic fields are solved by using the concept of vector potential. The free surface of magnetic fluid is formed by the balance of surface force, gravity, pressure difference, magnetic normal pressure and magnetic body force. The deformations of free surface of magnetic fluid are qualitatively clarified. And, the patterns of steady non-uniform magnetic fields induced by a circular current loop are quantitatively presented. The shape of free surface attained by the polar fluid approach is rougher and higher than that attained by the quasi-steady approach.

• 대한조선학회논문집
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• 제51권5호
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• pp.435-449
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• 2014

The effects of the gravity field and the free surface on the cavity shape and the drag are investigated through a numerical analysis for the steady supercavitating flow past a simple two-dimensional body underneath the free surface. The continuity and the RANS equations are numerically solved for an incompressible fluid using a $k-{\epsilon}$ turbulence model and a mixture fluid model has been applied for calculating the multiphase flow of air, water and vapor using the method of volume of fluid and the Schnerr-Sauer cavitation model. Numerical solutions have been obtained for the supercavitating flow about a two-dimensional $30^{\circ}$ wedge in wide range of depths of submergence and inflow velocities. The results are presented for the cavity shape, especially the length and the width, and the drag of the wedge in comparison with those of the case for the infinite fluid flow neglecting the gravity and the free surface. The influences of the gravity field and the free surface on the aforementioned quantities are discussed. The length and the width of the supercavity are reduced and the centerline of the cavity rises toward the free surface due to the effects of the gravity field and the free surface. The drag coefficient of the wedge, however, is about the same except for shallow depths of submergence. As the supercavitating wedge is approaching very close to the free surface, it is found the length and the width of a cavity are shorten even though the cavitation number is reduced. Also the present result suggests that, under the influence of the gravity field and the free surface, the length of the supercavity for a certain cavitation number varies and moreover is proportional to the inverse of the submergence depth Froude number.

• 대한기계학회논문집B
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• 제27권8호
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• pp.1142-1149
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• 2003

The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank moving in harmonic or pitching motion. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the location of the free-surface filling any some fraction of cells with fluid. The time-dependent changes of free-surface height are used for visualization subject to several conditions such as fluid height, horizontal acceleration, sinusoidal motion, and viscosity. The free-surface heights were used for comparing wall-force, which is caused by sloshing of flows. Damping effects by baffles were extensively investigated for various conditions in terms of baffle shape and position.

• 한국분무공학회지
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• 제10권4호
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• pp.26-31
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• 2005

Today, the research to examine a fact that interaction between the air and the fluid free surface affects the steady state flow and air. We proved the interaction between vortex pairs and free surface on each condition that is created by the end of delta wings. Another purpose of this study is to investigate the effect of surface active material which call change the surface tension and we must consider when we refer to turbulent flow on surface tension. Therefore, this research examined the growth process of vortex pairs on condition of clean, contaminated free surface and wall after we made vortex pairs through counter rotating flaps. The results of this study suggest that vortex pairs in clean free surface rise safely but the vortex pairs in contaminated free surface and rigid, no slip is made secondary vortex or rebounding. However the secondary vortex in rigid, no slip is stronger than before. and we can find the vortex shape which roll up more completely. However, these will disappear by the effect of wall.

• 한국전산유체공학회지
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• 제11권4호
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• pp.9-13
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• 2006

In the present study, a numerical analysis of transient mixer flow is performed considering free surface formation. The flow patterns and free surface shape in a mixers formed by flat paddle and pitched paddle impellers are predicted. In a flat paddle mixer, two flow circulation regions are formed due to strong radial flow, whereas one large circulation is formed in a pitched paddle mixer due to axial downward flow. These differences affect the free surface evolution and shape. It is seen from the results that a flat paddle mixer gives deeper free surface at center region than a pitched paddle mixer. The free surface of 8-blades-flat-paddle mixer is also simulated to compare with the available experimental and simulation results. The present computational results agree reasonably well with the experimental data.

• 한국소음진동공학회논문집
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• 제15권1호
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• pp.96-104
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• 2005

The coupled vibration characteristics for the fluid-structure interaction systems are investigated through the finite element method. The present paper is focused on vibration characteristics of the cylindrical fluid-storage tank with a baffle. The tank is partially filled with an inviscid and irrotational fluid having a free surface. A baffle is assumed here to have the shape of a thin annular plate and a conical shell, attached to the cylindrical tank and positioned below the fluid surface. The liquid domain is limited by a rigid flat bottom. As the effect of free surface waves is taken into account in the analysis, the bulging and sloshing modes are studied. To demonstrate the validity of present results, they are compared with the published ones. The effect of positions and inner-to-outer radius ratio of annular baffle and setting angles of conical baffle on coupled vibration characteristics is investigated.