• Composites Research
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• 제34권4호
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• pp.233-240
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• 2021

VaRI(Vacuum assisted Resin Infusion) 공정은 공정비용이 저렴하며, 크기가 큰 복합재 제작에 적합한 OoA(Out of Autoclave) 공정이다. VaRI 공정에서는 원할한 수지 주입을 위해 섬유 상단에 유로망을 적층한다. 수지는 이 유로망을 따라 섬유의 면 방향으로 빠르게 공급되고, 공급된 수지는 다시 섬유의 두께방향으로 함침된다. 면방향의 유동과 두께방향의 유동이 동시에 일어나기 때문에 수지의 유동을 예측하기 힘들며, 수지 주입과정을 예측하기 위해 3D 수치해석 프로그램이 사용되고 있다. 하지만, 3D로 해석하기 위해서 섬유와 유로망의 두께방향에 많은 Element가 필요하고, 이로 인해 제품의 크기가 클수록 해석시간이 오래 걸린다. 따라서 본 연구에서는 3D 유동해석을 2D 해석으로 간소화하여 유동해석에 소요되는 시간을 줄이는 방법을 제시하였다. 3D 유동해석과 간소화된 2D 유동해석을 동일조건에서 비교하여 효용성을 검증하였고, 충진시간 오차율은 약 7%, 유동해석시간 감소율은 약 95%로 나타났다. 또한 3D 해석에서 섬유 상, 중, 하단 간의 유동 전진 거리의 차이가 일정하다는 것을 활용하여 간소화된 2D 유동해석에서도 상, 중, 하단의 유동 전진 거리를 예측할 수 있었다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2007년도 학술발표회 논문집
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• pp.1287-1292
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• 2007

Recently, the frequency of unexpecting heavy rains has been increased due to abnormal climate and extreme rainfall. There was a limit to analyze 1D or 2D stream flow that was applied simple momentum equation and fixed energy conservation. Therefore, hydrodynamics flow analysis in rivers has been needed 3D numerical analysis for correct stream flow interpretation. In this study, CFD model on FLOW-3D was applied to stream flow analysis, which solves three dimenson RANS(Reynolds Averaged Navier-Stokes Equation) control equation to find out physical behavior and the effect of hydraulic structures. Numerical simulation accomplished those results was compared by using turbulence models such as ${\kappa}-{\varepsilon}$, RNG ${\kappa}-{\varepsilon}$ and LES. Those numerical analysis results have been illustrated by the turbulence energy effects, velocity of flow distributions, water level pressure distributions and eddy flows around the piers at Jangwall bridge in urbarn stream.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2001년도 춘계 학술대회논문집
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• pp.1-8
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• 2001

A CFD-based design method for transonic axial compressor blades was developed based on three-dimensional Navier-Stokes flow physics. The method employs a sectional three-dimensional (S3D) analysis concept where the three-dimensional flow analysis is performed on the grid plane of a span station with spanwise flux components held fixed. The S3D analysis produced flow solutions nearly identical to those of three-dimensional analysis, regardless of the initialization of the flow field. The sectional design based on the S3D analysis can include three-dimensional effects of compressor flows and thus overcome the deficiencies associated with the use of quasi-three-dimensional flow physics in conventional sectional design. The S3D design was first used in the inverse triode to find the geometry that produces a specified target pressure distribution. The method was also applied to optimize the adiabatic efficiency of the blade sections of Rotor 37. A new blade was constructed with the optimized sectional geometries at several span stations and its aerodynamic performance was evaluated with three-dimensional analyses.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2007년도 정기총회 및 학술발표대회
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• pp.603-607
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• 2007

Recently, the frequency of unexpecting heavy rains has been increased due to abnormal climate and extreme rainfall. There was a limit to analyze one dimension or two dimension stream flow of domestic rivers that was applied simple momentum equation and fixed energy conservation. Therefore, hydrodynamics flow analysis in rivers has been needed three dimensional numerical analysis for correct stream flow interpolation. In this study, CFD model on FLOW-3D was applied to stream flow analysis, which solves three dimension RANS(Reynolds Averaged Navier-Stokes Equation) control equation to find out physical behavior and the effect of hydraulic structures. Numerical simulation accomplished those results was compared by using turbulence models such as $k-{\backepsilon}$, RNG $k-{\backepsilon}$ and LES. Those numerical analysis results have been illustrated to bends and junctions by the turbulence energy effects, velocity of flow distributions, water level pressure distributions and eddy flows.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.194-199
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• 2007

IB (immersed boundary) method is one of the prominent tool in computational fluid dynamics for the analysis of flows over complex geometries. The IB technique simplyfies the solution procedure by eliminating the requirement of complex body fitted grids and it is also superior in terms of memory requirement. In this study we have developed numerical code (FOTRAN) for the analysis of 2D flow over a cylinder using IB technique. The code is validated by comparing the wake lengths and separation angles given by Guo et. al. We employed fractional-step procedure for solving the Navier-Stokes equations governing the flow and discrete forcing IB technique for imposing boundary conditions. Also we have developed a 3D code for the backward-facing-step flow and flow over a sphere. The reattachment length in backward-facing-step flow was compared with the one given by Nie and Armaly, which has proven the validity of our code.

• Composites Research
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• 제15권6호
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• pp.1-7
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• 2002

VARTM공정에서는 수지유동을 빠르게 하기 위해 투과촉진층이 사용되는데 투과촉진층과 섬유층 사이의 수지 속도차가 크다. VARTM제품은 길이에 비해서 두께가 얇으나 두 가지 다른 유통 매질 사이에 발생하는 lead-lag 유통을 관찰하기 위해서는 두께 방향을 고려한 3차원해석이 요구된다. 그런데 3차원 해석에 있어서 계산 시간이 문제가 된다. 일반 PC로 절점수가 많은 3차원 문제를 해석하려면 오랜 시간이 소요되므로 비실용적이다. 그래서 본 연구에서는 dual-scale 기법을 도입하여 전체 영역은 2.5차원으로 해석하고 주요한 관심 영역만을 3차원으로 해석하였다. 2.5차원 시뮬레이션만으로 예측하기 어려운 lead-lag 유동과 같은 특이한 유동 경향을 국부적인 3차인 해석을 통해서 발견학 수 있었다. 본 연구에서 개발된 global-local 해석기술은 일반 PC에서 적당한 계산 시간 내에 균일하지 않은 유동 매질 사이를 지나는 유동흐름의 특성 분석에 효과적으로 사용될 수 있다.

• 한국환경과학회지
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• 제21권4호
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• pp.471-478
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• 2012

In this study, the flow characteristic analysis at the curved-channel of the actual channel section is compared and reviewed using the 2D RMA-2 model and the 3D FLOW-3D model. the curve section with curve rate 1.044 in the research section is analyzed applying the frequency of he project flood of 100 years. According to the result, the issue for the application of the FLOW-3D Model's three-dimensional numeric analysis result to the actual river is found to be reviewed with caution. Also, application of the 3D model to the wide basin's flood characteristic is determined to be somewhat risky. But, the applicability to the hydraulic property analysis of a partial channel section and the impact analysis and forecast of hydraulic structure is presumed to be high. In addition, if the parameters to reflect the vegetation of basin and the actual channel, more accurate topological measurement data and the topological data with high closeness to the current status are provided, the result with higher reliability is considered to be drawn.

• 수산해양기술연구
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• 제56권3호
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• pp.230-237
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• 2020

In order to design a diesel engine system and predict its performance, it is necessary to analyze the gas flow of the intake and exhaust system. A gas flow analysis in three-dimensional (3D) format needs a high-resolution workstation and enormous time for analysis. Therefore, the method of characteristics (MOC) was used for a gas flow analysis with a fast calculation time and a low-resolution workstation. An experiment was conducted on a single cylinder diesel engine to measure pressure in cylinder, intake pipe and exhaust pipe. The one-dimensional (1D) gas flow was analyzed under the same conditions as the experiment. The engine speed, valve timing and compression ratio were the same conditions and the intake pressure was inputted as the experimental results. Bent pipe such as an exhaust port that cannot be realized in 1D was omitted. As results of validation, the cylinder pressure showed accuracy, but the exhaust pipe pressure exhibited inaccuracy. This is considered as an error caused by the failure to implement a bent pipe such as an exhaust port. When analyzed in 3D, calculation time required 61 hours more based on a model of this study. In the future, we intend to implement a bent pipe that cannot be realized in 1D using 3D and prepare a method to supplement reliability by using 1D-3D coupling.

• Tribology and Lubricants
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• 제25권3호
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• pp.150-156
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• 2009

Precise leakage prediction for annular type seals of turbomachinery is necessary for enhancing their efficiency and various prediction methods have been developed. As the seal passage is designed intricately, the analysis based on Bulk-flow concept which has been mainly used in predicting seal leakage is limited. In order to improve the seal leakage prediction, full Navier-Stokes Equations with turbulent model derived in the seal flow passage have to be solved. In this study, 3D CFD (Computational Fluid Dynamics) analysis has been performed for predicting leakage of various non-contact type anular seals using FLUENT. Compared to the results by Bulk-flow model analysis, experiment, and 2D CFD analysis, the result of 3D CFD analysis shows improvement in predicting seal leakage, especially for the parallel grooved pump seal.

• 한국지반공학회논문집
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• 제22권10호
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• pp.69-76
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• 2006

지하수흐름에 대한 신뢰성 해석을 실시하였으며, 흐름에 관여하는 매개변수들이 목표 값의 파괴확률을 초과하는데 미치는 영향을 알아보았다. 본 연구를 위하여 2차원 지하수흐름 프로그램을 3-D 프로그램 DGU-FLOW로 확장하여 제작하고, 이를 1계 및 2계 신뢰성 프로그램에 연계하였다. 3차원 흐름 프로그램의 검증은 지하굴착지반의 지하수 흐름 해석 문제를 풀고 이를 MODFLOW 프로그램과 비교하여 수행하였다. 신뢰성부분 또한 몬테칼로 해석을 수행하여 나타난 파괴확률을 비교함으로써 검증하였으며 지하수 흐름에 대한 1계 및 2계 신뢰성해석을 수행하여 산정된 파괴확률 값은 몬테칼로 해석을 통하여 나온 값과 매우 근접하였다. 토질층의 투수계수에 대한 매개변수 해석결과 투수계수의 평균과 분산의 증가는 목표 수량을 초과하는 파괴확률의 증가를 가져오는 것으로 나타났다. 또한 파괴확률의 민감도는 여러흐름 변수중에서 흐름영역 경계부의 일정 수두에 가장 민감한 것으로 나타났다.