• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.43-48
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• 2003

When the Eulerian-Lagrangian method is used to analyze the particle laden two-phase flow, a large number of particles should be used to obtain statistically meaningful solutions. Then it takes too much time to track the particles and to average the particle properties in the numerical analysis of two-phase flow. The purpose of this paper is to reduce the computation time by means of a set of particle gird separate to the flow grid. Particle motion equation here is the simplified B-B-O equation, which is integrated to get the particle trajectories. Particle turbulent dispersion, wall collision, and wall roughness effects are considered but the two-way coupling effects between gas and particles are neglected. Particle laden 2-D channel flow is solved and it is shown that the computational efficiency is indeed improved by using the current method

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.39-41
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• 1993

This paper presents the development of interactive graphical software for the educational purpose of power flow(PF) calculation. The developed software is specially designated to give a beginner the interest on PF problem as well as to increase the understanding of it with ease. the software developed in this paper is basically composed of the pull-down menu driver, in which various functions, such as Program Master, Data File Management, Case Study Option, PF Run and View Output, are prepared to handle the software easily and thus to be familiar with power flow calculation. A special design is also considered for interactive operation of the software, wi th which user can interrupt the computation process of PF to control the convergency of PF algorithm, With this function begineer can acquire the understanding of convergency characteristics and numerical sensitivity of PF algorithm as well as basic concept of its computation logic. Futhermore, various graphic illustrations is also provided to review and compare the computation results on monitor.

• Journal of Advanced Marine Engineering and Technology
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• 제26권6호
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• pp.670-678
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• 2002

Fluid flow in a rectangular duct with $90^{\circ}$ mitered elbow is measured by 5W laser doppler velocity meter. The fluid flow is also computed by commercial software of STAR-CD for comparison between measured and computed velocity profiles in the duct. Reynolds numbers for the comparison are 1,608 and 11,751 based on mean velocity and hydraulic diameter of the duct. First, the fluid flow of Reynolds number equal to 1,608 is predicted by assumptions of both laminar and turbulent models. But, even though the Reynolds number is less than 2,300~3,000, the computation by turbulent model is closed to the experimental data than that by laminar model. Second, the computation for Reynolds number of 11,751 by turbulent model also predicted the experimental data satisfactorily.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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• pp.57-62
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• 2004

Streamline simulation researches have been extensively accomplished due to the swiftness of computation and the reduction of numerical dispersion. In this study, we developed a streamline simulation model using a semianalytical solution of ID transport equation. To validate accuracy of the developed model, we compared simulation results of contaminant transport, which were acquired by streamline simulation models using an analytical solution, a numerical solution, and a semianalytical solution. The developed model using the semianalytical solution matched well with the model using an analytical solution. However, streamline simulation model using a numerical solution showed numerical dispersion. For an advection-dominant flow, there was little difference in the simulation results between the developed model and tile analytical model, but the differences between the analytical model and the numerical model were cleary shown. From the comparison of computing time we know that the streamline simulation using the semianalytical solution is 2-60 times as fast as the streamline simulation using the numerical solution.

• 인지과학
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• 제20권3호
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• pp.335-355
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• 2009

위험정보를 확률이나 빈도양식으로 제시하고 질병으로 사망할 확률(기저율)에 대한 위험을 판단하게 하고 양성판정을 받은 사람이 질병에 걸렸을 확률(사후확률)에 대한 위험판단과 추론의 정확성을 비교하였다. 베이스 추론 과제를 사용한 연구 1에서 숫자양식의 효과가 관찰되었다. 참가자들은 위험이 확률보다는 빈도로 제시될 때 더 위험하다고 판단하였고 질병에 걸렸을 확률을 더 정확하게 추론하였다. 빈도의 범위가 좁을 때보다 넓을 때 더 위험하다고 판단하는 효과는 관찰되지 않았다. 분석적 사고체계가 위험판단에 미치는 영향을 검토하려고 사후확률을 계산하는 조건과 계산하지 않는 조건을 비교하였다. 숫자양식의 효과는 여전히 관찰되었다. 연구 2는 기저율과 사후확률의 크기에 따라 숫자양식 효과와 빈도범위 효과가 달라지는지 알아보았다. 숫자양식의 효과는 기저율과 사후확률의 크기에 상관없이 모든 조건에서 관찰되었다. 위험한 사건이 발생할 확률의 높고 낮음에 상관없이 빈도로 제시되었을 때 참가자들이 더 위험하다고 판단하였다. 그러나 빈도범위 효과는 기저율이 낮은 조건에서만 발견되었다. 본 연구의 결과들을 이중처리체계 이론과 관련시켜 논의하였다.

• 지질공학
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• 제19권2호
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• pp.205-215
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• 2009

지표하 다공성매체에서 비정상상태의 유동을 해석하기 위한 종래의 수치적 모형들은 초기 건조한 토양으로의 강우로 인한 침투와 같은 한계적인 유입경계조건인 경우에 국지적 유동영역으로 인해 수치적 진동 및 불안정성을 초래한다. 이러한 경우 주로 공간적으로 세분된 격자와 작은 계산시간 간격을 요구하는데 이는 계산의 효율성을 떨어뜨린다. 따라서 본 연구에서는 유입 경계조건을 포함하는 비정상 상태의 지표하 유동해석을 위해 입자추적 알고리즘을 적용하여 불연속영역에서의 수치적 불안정성을 제거하고자 하였다. 즉, 수치적 안정성이 개선된 혼합 LE 유한요소기법을 제시하였다. 제시된 모형의 수치적 검증을 위해 비정상 균일 유동장과 불균일 유동장의 가상예제에 적용한 결과 해석해와 유사한 결과를 얻을 수 있었고 이를 토대로 함양 및 양수에 대한 3차원 가상유역 모의에 적용되었다. 본 연구에서 제시한 입자추적 알고리즘은 포화 및 불포화 다공성 매체의 유동을 보다 실질적으로 모의할 수 있으며 계산의 정확성 및 안정성에 크게 기여할 것으로 판단되었다.

• 한국측량학회지
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• 제15권1호
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• pp.51-61
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• 1997

전지구 해양의 조석 분포를 파악하기 위해 $1/3^\circ$의 분해능을 갖는 2차원 수치모형을 수립하여 반일분조$(M_2,\;S_2,\;K_2,\;N_2)$ 및 일분조$(K_1,\;O_1,\;P_1,\;Q_1)$의 조석도를 작성하였다. 수립된 $1/3^\circ$ 수치모형은 기존 수치모형에서 낮은 분해능으로 인하여 평가하지 못하였던 천해역 및 육붕해에서의 조석현상을 평가하는데 적용되었다 작성된 조석도는 기존의 수치모형 및 위성 고도계 자료로부터 작성된 조석도와 또, 심해의 일부 지역에서 관측된 조화상수와 상호 비교하였다. 세격자망에 의해 계산된 전지구 해양의 조석도는 위성을 통해 관측된 순간 해면 자료로부터 조석성분을 제거하여 시간에 따라 변화하지 않는 해면변위를 산정하는데 있어 유용한 자료로 이용될 수 있다.

• 한국해양공학회지
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• 제12권1호
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• pp.10-22
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• 1998

In the present work the elastic-plastic FE formulations using dynamic explicit time integration schemes are used for numerical analysis of a large auto-body panel stamping processes. For analyses of more complex cases with larger and more refined meshes, the explicit method is more time effective than implicit method, and has no convergency problem and has the robust nature of contact and friction algorithms while implicit method is widely used because of excellent accuracy and reliability. The elastic-plastic scheme is more reliable and rigorous while the rigid-plastic scheme require small computation time. In finite element simulation of auto-body panel stamping processes, the roobustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry conditions. The performnce of the dynamic explicit algorithms are investigated by comparing the simulation results of formaing of complicate shaped autobody parts, such as a fuel tank and a rear hinge, with the experimental results. It has been shown that the proposed dynamic explicit elastic-plastic finite element method enables an effective computation for complicated auto-body panel stamping processes.

• 천문학회보
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• 제36권1호
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• pp.34.1-34.1
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• 2011

Combining a detailed non-grey radiative transfer computation with the three dimensional hydrodynamics, we investigate a reliable numerical scheme for turbulent convection in the solar surface. The solar photosphere is the extremely turbulent region composed of partly ionized compressible gases in high temperature. Especially, the super adiabatic layer (SAL) near the solar photosphere is the shallow transition region where the energy transport varies steeply from convection to radiation. In order to describe physical processes accurately, a detailed treatment of radiative transfer should be considered as well as the high resolution computation of fluid dynamics. For a direct computation of radiation fields, the Accelerated Lambda Iteration (ALI) methods have been applied to hydrodynamical medium, incorporating the Opacity Distribution Function (ODF) as a realistic schemes for non-grey problems. Computational domain is the rectangular box of dimensions $42{\times}3Mn$ with the resolution of $1202{\times}190$ meshed grids, which covers several granules horizontally and 8 ~ 9 pressure scale heights vertically. During several convective turn-over times, the 3-D snapshots have been compiled with a second order accuracy. In addition, our radiation-hydrodynamical computation has been compared with the classical approximations such as grey atmospheres and Eddington approximation.

• Journal of applied mathematics & informatics
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• 제6권2호
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• pp.503-512
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• 1999

The purpose of this paper is to introduce the (Toeplitz) quadrature method for solving fredholm integral equations of the second kind with mildly singular kernels. We are presented some numerical examples for the computation of the error estimate using the MathCad package.