• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.2
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• pp.53-57
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• 2009

The dividing flow in an open channel has a number of distinctive characteristics. One of these is that the separation zone interacts with a secondary motion along the inner wall of a branch channel, generating sediment accumulation. To investigate this phenomenon, a two-dimensional numerical model based on the shallow-water equations, RMA2, which calculates water surface elevations and horizontal-velocity components, was used to analyze the dividing flow. The obtained numerical results fully coincide with the laboratory measurements reported by Hsu et al.(2002). For the analysis of the numerical results, a separation zone-discharge rate relationship was proposed. To reduce the size of a separation zone, the topographies of diagonal and curved edges were proposed, smoothly connecting the upstream corner to branch channel.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.4
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• pp.407-414
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• 2010

The fairway within the area of Yul-do and Songdo located near the Myeongnyang-sudo approaches south of Mokpo harbor is well guided by traffic separation scheme and other navigational aids. However, that part of the waterways where Yul-do is located sits at the cross-roads of marine traffic and is subjected to some potential risks in the voyage navigation: the effect of climatic phenomenon, the disregard of most ships in using the western sector of the fairway creating a congestion in the eastern sector, and lastly, the disadvantageous erect of the location and height of Yul-do island that hinders good lookout. This study investigates the environmental conditions that prevailed in the area in the span of 5-year period and the marine traffic situation taken from the data within the 72-hour period The navigational hazards and marine casualties are also be presented. The results are analyzed and are made the basis of a proposal for an improved separation of traffic. Thereafter, an evaluation is carried out by using the components of marine traffic flow simulation and ES modeling index. It is evaluated through simulation by the use of full-mission ship handling simulator.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2001.04a
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• pp.76-79
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• 2001

SIMULINK^{$\circledR}$를 이용하여 항공기용 터보프롭 엔진을 모델링한 후 현재 KT-1의 추진기관인 PT6A-62 분리축 터보프롭엔진의 성능을 해석하였다. SIMULINK^{$\circledR}$ 모델의 검증을 위하여 상용해석프로그램인 GASTURB 와 비교한 결과 최대오차율 1.07% 이내로 확인되었다. 지상정지 조건에서 블리드 공기유량을 0에서 5%, 보기류 구동에 따른 출력손실을 0에서 20 hp로 가정하고 해석한 결과 축마력은 최대 0.68%감소하며 비연료소모율은 거의 영향을 받지 않음을 알 수 있었다.

• Journal of the military operations research society of Korea
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• v.34 no.3
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• pp.13-29
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• 2008

The purpose of this study is to propose a model of the contract type and contract category in the process of programs in each stage which is the procurement by defence improvement program of a large long term programs. When requiring the contract, contractor confirms the contract type and contract category of the review the contract in bulk, separate contract by repeatedly. For the study of improvement method we used previous research paper, reports of DAP A and KIDA, laws of contract and other several materials. and we also applied the rational contract type and contract category for the general mass production program weapon system based on the analysis of contract states concluded with DAPA and old-DAPA, and collect the public opinions of the defense industry.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.77-82
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• 2013

A cyclone separator has been widely used in various industrial processes for removing fine particulate matter because it is easy to fabricate, cost effective, and adaptable to extremely harsh conditions. However, owing to the complex flow field in cyclones, a complete understanding of the detailed mechanisms of particulate removal has not yet been gained. In this study, a theoretical analysis was performed for calculating the collection efficiency and cut-off size in cyclones by taking into account the effects of geometrical and flow parameters. The collection efficiency and cut-off size values predicted by the theoretical model showed good agreement with experimental measurements for particles with a diameter of $0.5-30{\mu}m$. It was also revealed that the surface friction, along with the flow and geometrical parameters, has a significant effect on the cyclone performance.

• Journal of the Korean Electrochemical Society
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• v.9 no.4
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• pp.170-177
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• 2006

Optimum design of flow channel in the separation plate of Proton Exchange Membrane Fuel Cell is very prerequisite to reduce concentration over potential at high current region and remove the water generated in cathode effectively. In this paper, fully 3 dimensional computational model which solves anode and cathode flow fields simultaneously is developed in order to compare the performance of fuel cell with parallel and interdigitated flow channels. Oxygen and water concentration and pressure drop are calculated and i-V performance characteristics are compared between flows with two flow channels. Results show that performance of fuel cell with interdigitated flow channel is hi민or than that with parallel flow channel at high current region because hydrogen and oxygen in interdigitated flow channel are transported to catalyst layer effectively due to strong convective transport through gas diffusion layer but pressure drop is larger than that in parallel flow channel. Therefore Trade-off between power gain and pressure loss should be considered in design of fuel cell with interdigitated flow channel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3336-3344
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• 2014

The purpose of this study is small scale coagulation module is developed and demonstrated through a lab-scale test. Recent as a sewage treatment rate increases, have heightened the interest in the necessity on the nonpoint source and developing a small processing unit has been increased. Coagulation sedimentation module in this study is additional growth of floc through swirling in the outside zone, reduction of microstructure floc number and the internal settling zone through vertical/level flow complex sedimentation method after the coagulation process precipitation method as an effective high separation efficiency can be divided was also assessed. Coagulation sedimentation module can increase the load factor was 4.4 times compared to conventional clarifier base on the same volume and surface area through vertical/level flow. In this study, this process was selected formation and maintenance of swirling and uniform flow distribution in the internal settling zone as an important design factor, to derive its FLUENT was used to characteristics of the flow model. Through the simulation of swirling, influent velocity, dimensions of external basin, hopper depth of bottom cone was determined and through analysis of velocity distribution, flow distribution detailed specifications are derived like as diameter and number of effluent hole. Lab-scale($120{\ell}/hr$) test results, influent of 300~800 NTU to less than 10 NTU without polymer feeding was able to operate in the 20minutes retention time(surface loading rate $37.3m^3/m^2$-day), and through analysis FLUENT the possibility of using design parameters were derived.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.10
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• pp.667-673
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• 2017

We investigated the temperature uniformity in an anode-supported solid oxide fuel cell, using the open source computational fluid dynamics (CFD) toolbox, OpenFOAM. Numerical simulation was performed in three different flow paths, i.e., co-flow, counter-flow, and cross-flow paths. Gas flow in a porous electrode was calculated using effective diffusivity while considering the effect of interconnect rib. A lumped internal resistance model derived from a semi-empirical correlation was implemented for the calculation of electrochemical reaction. The result showed that the counter-flow path displayed the most uniform temperature distribution.

• KSBB Journal
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• v.5 no.1
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• pp.69-74
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• 1990

Dynamic characteristics of separation in membrane filtration system of tangential flow was investigated to find the functional relationship among the filtrate flux, transmembrane pressure, inulin concentration and recirculation rate. In case that NMWL is 1000, tracts-membrane pressure $0.4kgf/\;{\textrm{cm}^2}$ to $3.2kgf/\;{\textrm{cm}^2}$, inulin concentration lwt% to 5wt%, and recirculation rate 4ml / sec, mathematical model for the function among filtrate flux, transmembrane pressure, and inulin concentration was deduced and expressed as follows.Jv = (0.0022p + 0.0003) ln \frac{3p\;+\;2.1}{C_b}$ The values calculated by the above equation and those measured were compared to find to be nicely in accord with each other. Especially the agreement was enhanced in the region of higher concentration of inulin.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.236-236
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• 2022

연속적인 하천의 유량을 추정하기 위해서는 관측된 수위값을 유량으로 변환하기 위해 일반적으로 수위-유량 관계 곡선을 사용하며 수위구간 별로 일대일 관계로 제시된다. 그러나 유량을 추정함에 있어서 수위 외에도 하상경사, 조도계수와 같은 지형인자, 시간에 따른 유량의 변화와 같은 흐름요소를 모두 고려하여야 정확한 유량을 산정할 수 있다. 즉, 평상시에는 적합한 수준의 유량을 추정할 수 있다고 하더라도 조석의 영향이 있는 구간이나 홍수와 같이 시간에 따른 수위와 유량이 급변하는 경우에는 관측값과 수위-유량관계곡선을 이용한 추정값의 차이가 상당히 증가하여 유량 추정값의 활용이 부적합할 수 있다. 따라서 본 연구에서는 수위-유량관계곡선식의 적용이 어려운 조건에서 보다 정확한 유량을 추정하기 위해 1차원 유동해석모델을 이용한 계산 값과 관측 값과의 비교를 통해 정확도를 검토하고, 지점에 따라 차이가 발생되는 원인을 정성적으로 분석하고자 한다. 대상지점은 강우, 식생 등의 영향으로 수위와 유량의 관계를 단일 관계로 표현하기 어려워 구간분리가 발생된 지점으로 선정하였다. 흐름해석은 기지의 기점수위 조건으로부터 시작하며, 모델링을 통해 유량과 조도계수를 동시에 추정하였다. 분석 결과, 모델 내에서도 수위와 유량 관계의 루프형 특성, 조도계수의 변화를 대체적으로 잘 반영하는 것으로 나타났으며, 국내하천에서 유량추정의 정확도를 저하시키는 주된 원인에 대해 추정할 수 있었다. 향후 이 같은 방법을 통해 도출된 결과를 기반으로 수위-유량관계곡선의 불확실성을 평가하고, 유량 추정방식의 보완이 필요한 지점을 선별하는 기준에 대한 가이드라인을 제시할 수 있을 것으로 기대된다.