• 한국추진공학회지
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• 제26권5호
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• pp.35-43
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• 2022

본 연구에서는 고체추진제를 사용하는 closed bomb test(CBT)의 연소에 대한 정밀 모델링 및 해석을 수행하였다. 기상과 고상을 동시에 해석하기 위해 fluid structure interaction(FSI) 기법을 사용하였으며 기체상과 그레인의 연소해석은 Eulerian 방법을, 그레인의 이동은 Lagrangian 방법을 적용하였다. 고체상의 그레인과 연소가스의 상호 작용은 소스텀을 통해 완전 결합(fully coupled) 되도록 하였다. 그레인의 연소거리와 연소면의 이동을 모사하기 위하여 volume of fluid(VOF) 방법을 사용하였고, 그레인에 작용하는 힘은 그레인 연소면에 작용하는 압력과 중력을 고려하고, VOF의 속도항에 그레인 연소속도와 그레인 이동속도를 고려하였다. 개발한 수치모델을 바탕으로 1개와 3개 그레인에 대한 연소해석을 수행하여 실험결과와 비교 검증하였다. 연소시에 나타나는 압력 섭동에 대한 음향장을 분석하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1995년도 특별강연 및 추계학술발표 개요집
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• pp.34-38
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• 1995

• 대한기계학회논문집B
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• 제21권9호
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• pp.1230-1243
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• 1997

A numerical technique for simulating incompressible viscous flow with free surface is presented. The flow field is obtained by penalty finite element formulation. In this work, a modified volume of fluid (VOF) method which is compatible with 4-node element is proposed to track the moving free surface. This scheme can be applied to irregular mesh system, and can be easily extended to three dimensional geometries. Numerical analyses were done for two benchmark examples, namely the broken dam problem and the solitary wave propagation problem. The numerical results were in close agreement with the existing data. Illustrative examples were studied to show the effectiveness of the proposed numerical scheme.

• 대한조선학회논문집
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• 제48권4호
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• pp.317-324
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• 2011

When a ship proceeds in confined water, like canal, the water ahead of ship is pushed by hull. This pushed water returns to the side and under the hull, and this returned water will make fluid velocity higher at the side and under the hull, compared to the case in the infinite water depth. Due to the higher velocity, the pressure under the hull will decrease, resulting in the ship drop. This phenomenon is called "ship squat" and ship squat will result in various marine accidents. In this paper, for predicting ship squat, numerical calculation was carried out using commercial CFD code, FLUENT. To confirm wave pattern profile around the ship, VOF(Volume of Fluid) method was applied. The calculated results were compared with other paper's results and empirical methods.

• 한국주조공학회지
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• 제12권5호
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• pp.378-389
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• 1992

A numerical model based on the SOLA-VOF method, which can calculate the transient free-surface configuration of the melt, has been developed in order to analyze melt flow in the investment mold. The computational results were compared with experimental results obtained from pure aluminum investment casting. Heat transfer analysis, with and without consideration of melt flow effect has been performed. It can be concluded that analysis of melt flow in the investment mold, provides the optimum conditions for gating design. It also enables more precise solidification simulation, since heat loss, while filling the thin and complex investment mold, plays an important role in determining the solidification sequence.

• 한국해양공학회지
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• 제24권6호
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• pp.16-22
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• 2010

In this paper, the diffraction problems for fixed offshore structures are solved using a hybrid scheme. In this hybrid scheme, potential-based solutions and the Navier-Stokes-based finite volume method (FVM) with a volume-of-fluid (VOF) method are combined. We introduce a buffer zone for efficient wave-making and damping. In this buffer zone, the near field solution from FVM-VOF is gradually changed to Stokes' 2nd order wave solutions. Three different models, including the truncated cylinder, sphere, and wigleyIII model, are numerically investigated in regular waves with a wave steepness of 1/30. The efficiency and accuracy of the hybrid scheme are numerically validated from results using different domain sizes and buffer zones. The wave exciting forces from the FVM-VOF simulations are compared with experiments and potential-based solutions from the higher-order boundary element method (HOBEM). This comparison shows good agreement between the hybrid scheme and potential-based solutions.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.377-381
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• 2006

Recently, as economy grow and population increase we need to develop our coastal area and make good use of it for various purposes. That's why large structures are being installed on the sea. Some samples are petroleum storage tanks, pier of sea bridges. These are large structures which have been installed at coastal area. When we design such vertical cylinder, we should avoid too much construction expense caused by excessive designing or by lack of sufficient design. In order to prevent excessive expenditure, it is important to correctly calculate the force of waves acting on structures and predict the wave transformation. In this study, apply to VOF method based on Navier-Stokes equation and then discussed that nonlinear wave force and wave transformation. A comparison between the numerical model and existing experimental results showed nice agreement among them.

• 한국생산제조학회지
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• 제21권6호
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• pp.946-953
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• 2012

When water shortage has been getting worse recently, toilet water-saving is one of the most effective way to solve the water shortage. Therefore, in this study, toilet flushing performance was investigated with VOF(Volume Of Fluid) model to obtain the basic design data for the development of high-efficiency toilets. The result showed that the shorter trapway, the longer the flushing duration time. However, the shorter trapway is found to have disadvantage in exhausting dirt due to relatively weak siphon and higher curvature. Since the remaining water in a trapway appears to help siphon, it is also an important factor in developing high-efficiency toilets. Although higher water level in the water tank shows better performance in flushing, lower water level is preferred to save water. Too low water level may cause dirt to clog the trapway due to relatively weak siphon.

• 대한조선학회논문집
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• 제51권5호
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• pp.409-418
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• 2014

Simulation of flow past a complex marine structure requires a fine resolution in the vicinity of the structure, whereas a coarse resolution is enough far away from it. Therefore, a lot of grid cells may be wasted, when a simple Cartesian grid system is used for an Immersed Boundary Method (IBM). To alleviate this problems while maintaining the Cartesian frame work, we adopted an Adaptive Mesh Refinement (AMR) scheme where the grid system dynamically and locally refines as needed. In this study, We implemented a moving IBM and an AMR technique in our basic 3D incompressible Navier-Stokes solver. A Volume Of Fluid (VOF) method was used to effectively treat the free surface, and a recently developed Lagrangian Dynamic Subgrid-scale Model (LDSM) was incorporated in the code for accurate turbulence modeling. To capture vortex induced vibration accurately, the equation for the structure movement and the governing equations for fluid flow were solved at the same time implicitly. Also, We have developed an interface by using AutoLISP, which can properly distribute marker particles for IBM, compute the geometrical information of the object, and transfer it to the solver for the main simulation. To verify our numerical methodology, our results were compared with other authors' numerical and experimental results for the benchmark problems, revealing excellent agreement. Using the verified code, we investigated the following cases. (1) simulating flow around a floating sphere. (2) simulating flow past a marine structure.

• 한국해양환경ㆍ에너지학회지
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• 제13권1호
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• pp.12-17
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• 2010

OWC 파력발전장치는 에너지 변환장치로 널리 사용되고 있고 공기실의 작동성능을 향상시키기 위하여 파랑집중장치를 고안 하였다. 본 논문에서 사용된 수치조파수조는 two-phase VOF모델을 기반으로 하여 구현되었고 재생된 규칙 입사파는 공기실까지 전달되어 내부의 왕복 유동장을 형성하게 하였다. 수치조파수조는 연속방정식, Reynolds-averaged Navier-Stokes방정식, two-phase VOF 법으로 구성 되였고 standard k- 난류모델, 유한체적법, NITA-PISO 알고리즘 그리고 dynamic mesh기능을 채택하였다. OWC 공기실 파랑집중장치의 성능에 대하여 수치적으로 고찰하였다.