• 상하수도학회지
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• 제24권3호
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• pp.295-305
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• 2010

Role of the perforated pipe is to drain the water with equal pressure and velocity through the holes of perforated pipe. The perforated pipe is being used in many processes of water treatment system, however, the design parameter of perforated pipe is not standardized in korea. In this study, we have found the design parameter of perforated pipe in the water treatment system using the Computational Fluid Dynamics (CFD). The uniformity of outflow from the perforated pipe is directly affected according to area ratio(gross area of holes/surface area of the perforated pipe). In other words, the uniformity of outflow is improved as area ratio is smaller. Also, at the same area ratio, the uniformity of outflow is improved as number of holes is increase. Specially, in case of the two holes per length of pipe diameter(2/D) shows the most uniformity of outflow and the best hydraulic with the smaller pressure drop. The uniformity of outflow is aggravated and the pressure drop of pipe is decrease as length of pipe is longer. In case of that pipe length is 10m and above, the pressure drop decreased about 30% when diameter ratio is 40% with 0.2% of area ratio by comparison with 0.1% of area ratio.

• 공업화학
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• 제20권1호
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• pp.104-108
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• 2009

본 연구에서는 이산화탄소/수소 혼합기체가 관 모양의 Pd-Ag 막을 통과할 때 관 안에서의 이산화탄소 및 수소의 몰분율, 수소 분압, 그리고, 속도 구배 등을 CFD (Computational Fluid Dynamics) 기법을 사용하여서 다양한 유입 속도에 대해서 모사하였다. 모사 결과에 의하면 유입 속도가 증가할수록 관의 길이 방향을 따라서 이산화탄소의 몰분율이 더디게 증가함을 알 수 있었다. 또한, 혼합 기체의 유입 속도와 관의 길이가 수소 회수율에 미치는 영향에 대해서 살펴보았으며 낮은 유입속도와 긴 관의 경우에 수소 회수율이 큰 것을 알 수 있었다.

• 한국해양공학회지
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• 제34권4호
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• pp.237-244
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• 2020

In this study, we investigate surge force, heave force, and pitch moment, which are vertical plane hydrodynamics acting on Manta-type unmanned underwater vehicles (UUVs), using a model test and computational fluid dynamics (CFD) simulation. Assessing the maneuvering hydrodynamic characteristic of an underwater glider in the initial design stage is crucial. Although a model test is the best approach for obtaining the maneuvering hydrodynamic derivatives for underwater vehicles, numerical methods, such as Reynolds averaged Navier-Stokes (RANS) equations, have been used owing to their efficiency in terms of time and cost. Therefore, we conducted an RANS-based CFD calculation and a model test for Manta-type UUVs. In addition, we conducted a validation study through a comparison with a model test conducted at a circular water channel (CWC) in Korea Maritime & Ocean University Furthermore, two RANS solvers (Star-CCM+ and OpenFOAM) were used and compared. Finally, the maneuvering hydrodynamic forces obtained from the static drift and resistance tests for a Manta-type UUV were presented.

• 한국항해항만학회지
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• 제27권2호
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• pp.239-246
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• 2003

해양에 기름이 유출되면 방제작업의 초기단계에서 기름의 이동 및 확산을 차단하기 위하여 오일 붐을 사용하는 것이 일반적이다. 그러나 오일 붐은 유속, 기름의 밀도와 점성, 수심, 기름의 양, 그리고 붐 흘수의 길이 등과 같은 여러 인자들에 의해 그 포획능력이 영향을 받는다. 본 연구에서는 이들 누유인자가 오일 붐의 포획과정에 어떠한 영향을 미치는지를 체계적으로 파악하기 위하여 컴퓨터 모델링을 수행하였다. 모델링을 위하여 CFD(computational fluid dynamics) 프로그램 중에서 가장 널리 알려진 Fluent를 이용하였으며 기존의 실험자료와 비교함으로써 모델링 결과를 검증하였다. 본 연구의 결과는 방제작업 책임자와 오일 붐 설계자에게 유용한 참고자료가 될 것으로 기대된다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2003년도 춘계공동학술대회논문집
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• pp.171-178
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• 2003

해양에 기름이 유출되면 방제작업의 초기단계에서 기름의 이동 및 확산을 차단하기 위하여 오일 붐을 사용하는 것이 일반적이다. 그러나 오일 붐은 유속, 기름의 밀도와 점성, 수심, 기름의 양, 그리고 붐 홀수의 길이 등과 같은 여러 인자들에 의해 그 포획능력이 영향을 받는다. 본 연구에서는 이들 누유인자가 오일 붐의 포획과정에서 어떠한 영향을 미치는지를 체계적으로 파악하기 위하여 컴퓨터 모델링을 수행하였다. 모델링을 위하여 CFD(computational fluid dynamics) 프로그램 중에서 가장 널리 알려진 Fluent를 이용하였으며 기존의 실험자료와 비교함으로써 모델링 결과를 검증하였다. 본 연구의 결과는 방제작업 책임자와 오일 붐 설계자에게 유용한 참고자료가 될 것으로 기대된다.

• Tribology and Lubricants
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• 제25권1호
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• pp.43-48
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• 2009

It is reported by many researchers that the textured bearing surfaces, where many tiny micro-pockets or enclosed recesses were incorporated, can enhance the load support and reduce friction force. Recently, the basic lubrication mechanism of micro-pocketed parallel surfaces are explained in terms of "inlet suction" using continuity equation and simply cavitation condition. However, it is required that more actual cavitation condition in the pocket region should be applied to estimate exact bearing performance. In this paper, a commercial computational fluid dynamics (CFD) code, FLUENT is used to investigate the exact lubrication characteristics of infinitely long slider bearing with micro-pockets. The results show that the pressure distributions are highly affected by pocket depths, its positions and numbers. The numerical method adopted in this paper and results can be use in optimal design of textured sliding bearings.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2157-2163
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• 2018

Catalytic reactors have been essential for chemical engineering process, and different designs of reactors in multi-scales have been previously studied. Computational fluid dynamics (CFD) utilized in reactor designs have been gaining interest due to its cost-effective advantage in designing the actual reactors before its construction. In this work, butadiene synthesis via oxidative dehydrogenation (ODH) of n-butene using tubular reactor was used as a case study in the CFD model. The effects of coolant and reactor diameter were investigated in assessing the reactor performance. Based on the results of the CFD model, the conversion and selectivity were 86.5% and 59.5% respectively in a fixed bed reactor under adiabatic condition. When coolants were used in a tubular reactor, reactor temperature profiles showed that solar salt had lower temperature gradients inside the reactor than the cooling water. Furthermore, higher conversion (90.9%) and selectivity (90.5%) were observed for solar salt as compared to the cooling water (88.4% for conversion and 86.3% for selectivity). Meanwhile, reducing the reactor diameter resulted in smaller temperature gradients with higher conversion and selectivity.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2835-2843
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• 2023

After an emergency shutdown of a lead-bismuth fast reactor, thermal stratification occurs in the upper Plenum, which negatively impacts the integrity of the reactor structure and the residual heat removal capacity of natural circulation flow. The research on thermal stratification of reactors has mainly been conducted using an experimental method, a system program, and computational fluid dynamics (CFD). However, the equipment required for the experimental method is expensive, accuracy of the system program is unpredictable, and resources and time required for the CFD approach are extensive. To overcome the defects of thermal stratification analysis, a high-precision full-order thermal stratification model based on CFD technology is prepared in this study. Furthermore, a reduced-order model has been developed by combining proper orthogonal decomposition (POD) with Galerkin projection. A comparative analysis of thermal stratification with the proposed full-order model reveals that the reduced-order thermal stratification model can well simulate the temperature distribution in the upper plenum and rapidly elucidate the thermal stratification interface characteristics during the lead-bismuth fast reactor accident. Overall, this study provides an analytical tool for determining the thermal stratification mechanism and reducing thermal stratification.

• Structural Engineering and Mechanics
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• 제82권4호
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• pp.517-542
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• 2022

The effect of mean angle of wind attack on the flutter critical wind speed of two generic bridge deck cross-sections, viz, one closed box type streamlined section (deck-1) and closed box trapezoidal bluff type section with extended flanges/overhangs (deck-2) type of section have been studied using Computational Fluid Dynamics (CFD) based forced vibration simulation method. Owing to the importance of the effect of the amplitude of forcing oscillation on the flutter onset, its effect on the flutter derivatives and flutter onset have been studied, especially at non-zero mean angles of wind attack. The flutter derivatives obtained have been used to evaluate flutter critical wind speeds and flutter index of the deck sections at non-zero mean angles of wind attack studied and the same have been validated with those based on experimental results reported in literature. The value of amplitude of forcing oscillation in torsional degree of freedom for CFD based simulations is suggested to be in the range of 0.5° to 2°, especially for bluff bridge deck sections. Early onset of flutter from numerical simulations, thereby conservative estimate of occurrence of instability has been observed from numerical simulations in case of bluff bridge deck section. The study aids in gaining confidence and the extent of applicability of CFD during early stages of bridge design, especially towards carrying out studies on mean incident wind effects.

• Wind and Structures
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• 제14권5호
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• pp.435-447
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• 2011

A Computational Fluid Dynamics model is presented in this study for the simulation of the complex fluid flows with free surfaces inside the Tuned Liquid Column Dampers in horizontal motion. The characteristics of the fluid model of the TLCD in horizontal motion include the free surface of the multiphase flow and the horizontal moving frame. In this study, the time depend unsteady Standard ${\kappa}-{\varepsilon}$ turbulent model based on Navier-Stokes equations is chosen. The volume of fluid (VOF) method and sliding mesh technique are adopted to track the free surface of water inside the vertical columns of TLCD and treat the moving boundary of the walls of TLCD in horizontal motion. Several model solution parameters comprising different time steps, mesh sizes, convergence criteria and discretization schemes are examined to establish model parametric independency results. The simulation results are compared with the experimental data in the dimensionless amplitude of the water column in four different configured groups of TLCDs with four different orifice areas. The predicted natural frequencies and the head loss coefficient of TLCDs from CFD model are also compared with the experimental data. The predicted numerical results agree well with the available experimental data.