• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.337-342
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• 2001

A numerical study of three-dimensional fluid flow and heat transfer in the metering section of a single screw extruder has been performed. The mathematical model for the screw channel is simplified by unwound channel and fixing the coordinate system to the screw. The pressure boundary and the prescribed mass flow rate conditions are imposed on the inlet and outlet, respectively. The commercial code STAR-CD based on the finite volume method is used to obtain the results of the present work. The computation of the reverse flow, which cannot be computed by the marching-type 3-D model, is performed in the present study.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.86-96
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• 1998

A numerical study has been carried out of three-dimensional turbulent flows around a MIRA reference vehicle model both with and without wheels in computation. Two convective difference schemes with two k-$\varepsilon$ turbulence models are evaluated for the performance such as drag coefficient, velocity and pressure fields. Pressure coefficients along the surfaces of the model are compared with experimental data. The drag coefficient, the velocity and pressure fields are found to change considerably with the adopted finite difference schemes. Drag forces computed in the various regions of the model indicate that design change decisions should not rely just on the total drag and that local flow structures are important. The results also indicate that the RNG model with the QUICK scheme predicts fairly well the tendency of velocity and pressure fields and gives more reliable drag coefficient rather than the other cases.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.26-29
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• 2004

In this paper, we report the numerical and experimental solutions of the dynamic characteristics of a vortex ring in a circular cylinder generated by impinging a fluid blob from a hole on the bottom wall of the cylinder. We managed to visualize successfully the flow pattern shown on the vertical and horizontal planes by using a specially designed optical apparatus. Results of three-dimensional computation for the flow are shown to be in a satisfactory agreement with the experimental ones. We also report the experimental results which show a breaking of the axi-symmetric pattern after the vortex touches the free surface.

• 한국해안해양공학회지
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• 제7권2호
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• pp.176-197
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• 1995

한국경남해역의 2차원 및 3차원적 조류구조를 동적원리에 근거한 수치모형을 통하여 조사하였다. 2차원 수치모형을 이용하여 주 8개 분조(M$_2$, S$_2$, $K_1$, $O_1$, $N_2$, $K_2$, P$_1$, Q$_1$)에 대한 조석체계를 계산하였다. 계산결과는 해안의 관측치와 비교하여 만족할만한 일치를 보였다. 이러한 결과를 토대로 하여 매년 적조등으로 인해 심각한 오염이 발생되고 있는 진해만과 마산만의 3차원적 조석순환구조를 조사하기 위하여 기 수립된 2차원 모형과 내만의 3차원 모형을 연결시키도록 개선하였다. 그 방법으로 Davies(1980)가 제시한 2차원 수심적분 모형과 3차원 Galerkin-Spectral 모형과의 동적연결방법을 이용하였다. Davies의 연구에 추가하여 본 연구에서는 3차원 수치모형에 자승형마찰항과 비선형 이류항을 추가하였다. 3차원 모형에서 산정된 각 수심별 M$_2$ 분조의 조류타원도는 KORDI(1990)가 수행한 수심별 조류관측치와 양호한 일치를 보였다.

• 대한기계학회논문집B
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• 제27권6호
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• pp.753-765
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• 2003

A finite element code for the numerical solution of the Navier-Stokes equation is parallelized by vertex-oriented domain decomposition. To accelerate the convergence of iterative solvers like conjugate gradient method, parallel block ILU, iterative block ILU, and distributed ILU methods are tested as parallel preconditioners. The effectiveness of the algorithms has been investigated when P1P1 finite element discretization is used for the parallel solution of the Navier-Stokes equation. Two-dimensional and three-dimensional Laplace equations are calculated to estimate the speedup of the preconditioners. Calculation domain is partitioned by one- and multi-dimensional partitioning methods in structured grid and by METIS library in unstructured grid. For the domain-decomposed parallel computation of the Navier-Stokes equation, we have solved three-dimensional lid-driven cavity and natural convection problems in a cube as benchmark problems using a parallelized fractional 4-step finite element method. The speedup for each parallel preconditioning method is to be compared using upto 64 processors.

• 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.

• 한국전산유체공학회지
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• 제12권1호
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• pp.9-15
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• 2007

A three dimensional numerical model to predict the flow and transport of mixtures and also the electrochemical reactions in polymer electrolyte membrane (PEM) fuel cells is developed. The numerical computation is base on vorticity- velocity method. Governing equations for the flow and transport of mixtures are coupled with the equations for electrochemical reactions and are solved simultaneously including production and condensation of vapor. Fuel cell performance predicted by this calculation is compared with the experimental results and resonable agreements are achieved.

• 전산구조공학
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• 제6권2호
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• pp.103-114
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• 1993

유전적분형 물성방정식에 근거한 선형 점탄성문제의 효율적인 수치해석을 위해서 새로운 유한요소해법을 공식화하였다. 각 시간구간에서 변수변화를 선형적으로 가정하고 유전적분의 계산을 매우 효율적으로 처리하였다. 그 결과 과거의 해석법에 비하여 수치정확도 및 경제성에서 큰 향상을 얻었다.

• 한국전산유체공학회지
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• 제17권2호
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• pp.78-84
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• 2012

Numerical calculations were performed to investigate the influence in aerodynamic characteristics of a rotor system by surrounding structures and the ground effect for the rotor blade on a whirl tower is also investigated. Three dimensional Navier-Stokes simulations were carried out by using unstructured overset mesh technique and parallel computation. The calculated hover performance showed good agreement with the experimental result and showed that the structures around the whirl tower did not affect the aerodynamic characteristics of the blade. The ground effect was studied by comparing with the numerical result for the out of ground condition and the result of an analytic model.

• Journal of Advanced Marine Engineering and Technology
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• 제25권6호
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• pp.1324-1329
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• 2001

The depression of the external situation like the departure of WTO system and the plan of EEZ proclaim is forcing fishery into improving their fishing condition. By this international and domestic circumstance, development of the sea water cooling apparatus for fish hold storage is demanded sincerely. This study represents the thermal characteristics of the fish hold storage during transportation. The numerical analysis in this study is the finite volume method with the SIMPLE computational algorithm to study the seawater flow behavior in the fish hold storage. The computation were carried out with the variations of the circulating flow velocity and depth of fish hold storage. As the result of the three dimensional simulations, the mean temperature doesn't almost change by the circulating flow rate. find the mean temperature is suddenly changed by the ratio of depth of fish hold storage.