• 한국컴퓨터그래픽스학회논문지
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• 제10권4호
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• pp.13-21
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• 2004

This paper presents a physically based technique for simulating complex multiphase fluids. This work is motivated by the "stable fluids" method developed by Stam to handle gaseous fluids. We extend this technique to water, which calls for the development of methods for modeling multiphase fluids and suppressing dissipation. We construct a multiphase fluid formulation by combining the Navier-Stokes equations with the level set method. By adopting constrained interpolation profile (CIP)-based advection, we reduce the numerical dissipation and diffusion significantly. We further reduce the dissipation by converting potential1y dissipative cel1s into droplets or bubbles that undergo Lagrangian motion. Due to the multiphase formulation, the proposed method properly simulates the interaction of water with surrounding air, instead of simulating water in a void space. Moreover, the introduction of the non-dissipative technique means that, in contrast to previous methods, the simulated water does not unnecessarily lose mass and its motion is not damped to an unphysical extent. Experiments showed that the proposed method is stable and runs fast. It is demonstrated that two-dimensional simulation runs in real-time.

• 한국컴퓨터그래픽스학회논문지
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• 제10권3호
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• pp.52-60
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• 2004

This paper presents a physically based technique for simulating complex multiphase fluids. This work is motivated by the "stable fluids" method developed by Stam to handle gaseous fluids. We extend this technique to water, which calls for the development of methods for modeling multiphase fluids and suppressing dissipation. We construct a multiphase fluid formulation by combining the Navier-Stokes equations with the level set method. By adopting constrained interpolation profile (CIP)-based advection, we reduce the numerical dissipation and diffusion significantly. We further reduce the dissipation by converting potentially dissipative cells into droplets or bubbles that undergo Lagrangian motion. Due to the multiphase formulation, the proposed method properly simulates the interaction of water with surrounding air, instead of simulating water in a void space. Moreover. the introduction of the non-dissipative technique means that, in contrast 10 previous methods, the simulated water does not unnecessarily lose mass and its motion is not damped to an unphysical extent. Experiments showed that the proposed method is stable and runs fast. It is demonstrated that two-dimensional simulation runs in real-time.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.145-150
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• 2009

In this study, characteristics of microwave and convective drying are studied by using a multiphase porous media model. Temperature and moisture profiles for hot-air convective heating and microwave heating of 1-D porous media with varying time and space are numerically investigated. This result shows the microwave drying method is more effective than the convective drying method. Comparing to convective drying, microwave drying can increase temperature and evaporation rate significantly since microwave generates internal heat and increases internal pressure, which results in moisture movement toward the surface on which moisture is vaporized.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.627-630
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• 2002

A methodology based on factorial design and Motto Carlo methods is developed and implemented for incorporating uncertainties within a multiphase subsurface flow and transport simulation system. Due to uncertainties in intrinsic permeability and longitudinal dispersivity, the predicted output is also uncertain based on the well-developed multiphase compositional simulator. The simulation results reveal that the uncertainties in input parameters pose considerable influences on the predicted output, and the mean and variance of permeability will have significant impacts on the modeling output. The proposed method offers an effective tool for evaluating uncertainty in multiphase flow simulation system.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.808-812
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• 2010

A great deal of attention is focused on coupled Thermo-Hydro-Mechanical (THM) behavior of multiphase porous media in diverse geo-mechanical and geo-environmental areas. This paper presents general governing equations for coupled THM processes in unsaturated porous media. Coupled partial differential equations are derived from 3 mass balances equations (solid, water, and air), energy balance equation, and force equilibrium equation. Finite element code is developed from the Galerkin formulation and time integration of these governing equations for 4 main variables (displacement $\underline{u}$, gas pressure $P_g$, liquid pressure $P_l$), and temperature T). The code is validated with theoretical solutions for linear material with simple boundary conditions.

• 한국가스학회지
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• 제17권1호
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• pp.26-34
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• 2013

상 변화(phase change)를 수반한 다상 유동 연구(multiphase flow analysis)는 증발, 응축과 같은 많은 분야에 적용, 응용될 수 있고 현상의 복잡성 때문에 많은 연구의 관심을 받고 있는 분야이다. 본 연구에서는 극저온 유체인 액화질소가 다양한 밀도의 글라스 울 내부 다공성 매질속으로 스며들면서 나타나는 거동을 살펴보았다. 유동에 영향을 미치는 투과성 계수에 대해서, 외부 압력의 영향성에 대한 실험을 진행하였고 논의하였다. 극저온 유체인 액화질소를 실험유체로 사용하여 사각 기둥 실린더 내부의 유체의 유동에 대한 실험으로 유체의 유동을 살펴보았다. 그 결과 벌크 밀도가 커짐에 따라 투과성 계수가 작아지고, 거리에 따른 압력변화의 비선형성이 커짐을 보였다. 마지막으로 CFD 전산유동 프로그램으로 실험결과와 동일한 상황을 모사하였으며, 이를 실험결과와 비교 분석하였다. 이에 대한 검증결과, 시뮬레이션 결과가 실험결과와 유사한 경향과 결과를 보여주었다.

• 한국해양공학회지
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• 제28권6호
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• pp.517-526
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• 2014

The leakage of cryogenic LNG through cracks in the insulation membrane of an LNG carrier causes the hull structure to experience a cold spot as a result of the heat transfer from the LNG. The hull structure will become brittle at this cold spot and the evaporated natural gas may potentially lead to a hazard because of its flammability. This paper presents a computational model for the LNG flow and heat diffusion in an LNG insulation panel subject to leakage. The temperature distribution in the insulation panel and the speed of gas diffusion through it are simulated to assess the safety level of an LNG carrier subject that experiences a leak. The behavior of the leaked LNG is modeled using a multiphase flow that considers the mixture of liquid and gas. The simulation model considers the phase change of the LNG, gas-liquid multiphase interactions in the porous media, and accompanying rates of heat transfer. It is assumed that the NO96-GW membrane storage is composed of glass wool and plywood for the numerical simulation. In the numerical simulation, the seepage, heat diffusion, and evaporation of the LNG are investigated. It is found that the diffusion speed of the leakage is very high to accelerate the evaporation of the LNG.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1801-1807
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• 2001

In multiphase flne the bubble size and velocity. To achieve this, one of approaches is to utilize laser phase-Doppler anemometry. However, it was found that the second order refraction has great impact on PDA sizing method when the relative refractive index of media is less than one. In this paper, the problem of second order refraction is investigated and a model of phase-size correlation to eliminate the measurement errors is introduced for bubble sizing. As a result, the model relates the assumption of single scattering mechanism in conventional phase-Doppler anemometry. The results of simulations based on this new model by using Generalized Lorenz Mie Theory (GLMT) are compared with those based on the conventional method. An optimization method for accurately sizing air-bubble in water has been suggested.

• 천문학회보
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• 제35권1호
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• pp.66.1-66.1
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• 2010

Using two-dimensional numerical hydrodynamic simulations, we investigate the star formation rate (SFR) in turbulent, multiphase, galactic gaseous disks. Our simulation domain is axisymmetric, and local in the radial direction and global in the vertical direction. Our models include galactic rotation, vertical density stratification, self-gravity, radiative heating and cooling, and thermal conduction, but do not include spiral-arm features. Turbulence in our models is driven by momentum feedback from supernova explosion events occurring in localized dense regions formed by thermal and gravitational instabilities. Self-consistent radiative heating, representing enhanced/reduced FUV photons from the star formation, is also taken into account. By controlling three parameters (the gas surface density, the stellar disk density, and the angular rotation rate) that characterize local galactic disks, we explore how the SFR depends on the background environmental state. We also discuss the relation between the SFR and the gas surface density found in our numerical models in comparison with observations.

• 자원환경지질
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• 제44권2호
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• pp.161-170
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• 2011

석유공학분야에서 보고된 분율 흐름 접근 방식을 이용하여 물리적 또는 화학적으로 불균질한 매질에서 완전한 삼상유체를 고려할 수 있는 다상 흐름 수치 모의 프로그램인 CHMPS가 개발되었다. 이 프로그램은 석희준과 G.T. Yeh (2008)에 의해 개발된 MPS을 확장하였는데, 친수성이 NAPL 거동에 미치는 영향을 모의하기 위하여 개발되었다. 대부분 존재하는 모델들은 물리적으로 불균질한 매질을 고려하고 이상흐름과 특정한 경계조건에 국한되어 있다. 게다가 대부분의 모델들은 주로 water-wet 매질에만 국한되어 있다. 그러나 실제 존재하는 시스템에서는 water-wet과 oil-wet 매질 사이의 친수성의 변화는 종종 일어난다 더군다나 기름에 의한 다공성 매질의 젖음은 균등하기 보다는 불균질 또는 부분적일 수 있다. 왜냐하면 친수성에 영향을 미치는 요소들과 지하 매질이 불균질하기 때문이다. 따라서, 이번 연구에서는 물리적으로 불균질한 매질 뿐만 아니라 친수성 변에서 화학적으로 불균질한 매질을 CHEMPS을 활용하여 수치모의 하였다. 그 외에도 개개의 상에 대해서 유량 경계조건 및 고정경계조건의 두 가지 형식의 결합으로 표현되는 일반경계조건이 고려되었다.