• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2007년도 학술발표회 논문집
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• pp.846-850
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• 2007

In this study debris like branch or trash are washed and flowed from land to stream by rainfall runoff at mountain or urban stream specially rainy season. These kinds of debris are accumulated at hydraulic construct on the way of flow along the stream. The shape or ratio of like these accumulated debris are various according to the location where it is accumulated and the material what it is, so that it is influenced to be varied to flow characteristics. To be simple of accumulated debris shape, it was made experiments though the variation of open ratio and the shape of accumulated debris by lab experiment using straight channel with two piers. From the result, the water level is inverse proportion to open ratio, and the water level more sensitive to the debris‘ width than length at the same area of accumulated debris.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1321-1335
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• 2022

This study was conducted to investigate the effect of absorption coefficient models on the P1 radiation model for a premixed hydrogen flame containing the water vapor. A CFD combustion simulation analysis was performed using XiFoam, one of the open-source CFD solvers in OpenFOAM. The solver using the flamelet combustion model has been modified to implement radiative heat transfer. The absorption coefficient models used in this study the grey-mean model and constant model, and for comparison, case without radiation was added. This CFD simulation study consisted of benchmarking the THAI HD-15 and HD-22 experiments. The difference between the two tests is the inclusion of water vapor in the condition before ignition. In the case of the HD-22 experiment containing water vapor in the initial condition, the simulation results show that the grey-mean absorption coefficient model has a strong influence on the temperature decrease of the flame and on the change in pressure inside the vessel.

• International Journal of Fluid Machinery and Systems
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• 제7권4호
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• pp.174-182
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• 2014

The ultimate objective of this study is to develop a water turbine appropriate for low-head open channels to effectively utilize the unused hydropower energy of rivers and agricultural waterways. The application of a cross-flow runner to open channels as an undershot water turbine has been considered and, to this end, a significant simplification was attained by removing the turbine casing. However, the flow field of an undershot cross-flow water turbine possesses free surfaces, and, as a result, the water depth around the runner changes with variation in the rotational speed such that the flow field itself is significantly altered. Thus, clear understanding of the flow fields observed with free surfaces to improve the performance of this turbine is necessary. In this study, the performance of this turbine and the flow field were evaluated through experiments and numerical analysis. The particle image velocimetry technique was used for flow measurements. The experimental results reflecting the performance of this turbine and the flow field were consistent with numerical analysis. In addition, the flow fields at the inlet and outlet regions at the first and second stages of this water turbine were clarified.

• 물과 미래
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• 제28권5호
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• pp.235-238
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• 1995

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2016년도 학술발표회
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• pp.72-72
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• 2016

최근 발생하고 있는 기후변화로 인하여 하천 및 저수지의 수질문제가 커지고 있다. 특히 여름철 부영양화로 인해 발생하는 녹조현상은 사회적인 문제로 과학적인 수질사고에 대한 예측과 관리가 필요한 실정이다. 수질예보는 정기적으로 하천 및 저수지의 수질을 예측하여 사용자에게 제공하는 분석기법으로 수질현황을 파악하고 수질을 관리하고 의사결정을 하는데 도움을 줄 수 있다. 수질예보에 사용되는 모형은 유역모형, 하천모형, 저수지모형이 있으며, 이중 하천 및 저수지에 주로 적용되고 있는 3차원 수리수질모형의 경우 격자의 개수가 많아 모의시간이 길어지게 되고 이로 인해 일일 수질 예보가 어렵게 된다. 3차원 수리수질모형의 모의속도를 개선하는 방법에는 하드웨어의 성능을 높이는 방법과 병렬화를 이용한 소프트웨어적인 방법이 있다. 이중 하드웨어의 성능을 높이는 방법은 컴퓨터의 사양을 높이는 방법으로 높은 비용이 소요된다. 하지만 병렬화 방법은 컴퓨팅 기술의 발전으로 멀티코어가 대중화가 된 최근에 코드의 적용만으로 모의속도를 향상시킬 수 있다. 본 연구에서 사용된 모형은 서호주대학에서 개발한 3차원 수리 수질모형인 ELCOM-CAEDYM 모형으로 적용된 병렬화 기법은 OpenMP(Open Multi-Processing)방법이다. 기존 직렬 컴퓨팅 방식으로 구성되어 한번에 한 개의 명령어 밖에 처리할 수 없었던 작업방법을 동시에 여러 개의 처리요소를 이용하여 명령을 실행할 수 있게 하는 방식이다. 하지만 CPU의 개수는 제한되어 있으며, Amdahl's law에 따르면 OpenMP방식의 병렬화시 속도개선효과는 95% 병렬화 프로그램에서 최대 CPU 개수의 제한이 없다면 20배 까지 속도향상이 가능하다고 하였다. 본 연구에서는 3차원 수리 수질예측 모형인 ELCOM-CAEDYM에 적용된 병렬화 기법을 적용하는데 있어 최적 CPU사용 개수를 파악 하고자 하였으며, 이를 통해 수질예보시스템을 운영하는데 가장 효율적인 방법을 찾아 적용하고자 하고자 한다.

• 대한조선학회논문집
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• 제50권4호
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• pp.199-205
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• 2013

To research and develop an azimuth thruster, the new type of open water test dynamometers to measure thrust, torque, total thrust and duct force are designed and manufactured by Samsung Ship Model Basin(SSMB). A compact servomotor to be accurately controlled is connected to precise spiral bevel gear through shafting system combined by couplings and main shafts. The dynamometers have shown excellent linearity and repeatability for all components of forces and a torque. Also, the open water tests have been successfully performed to show the performance of the system. In near future, it is expected that the device can be used for the study of scale effects and development of azimuth thrusters.

• 한국해양공학회지
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• 제28권3호
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• pp.199-208
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• 2014

In this study, propeller open water characteristics ($K_P$, $K_T$ and ${\eta}_o$) were compared for three different ducted propellers using a Computational Fluid Dynamics (CFD) analysis, as well as an experimental test at a basin. The best shape of the duct was selected from the three types of specially designed ducts based on the CFD analysis results. The same propeller model (Kaplan type propeller) was used inside all three duct models, and the propeller open water characteristics were compared, predominantly at the design speed for an underwater vehicle. Finally, the results of the CFD test simulations for the selected duct case were verified by experimental open water tests in a towing tank.

• 산업공학
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• 제17권1호
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• pp.104-112
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• 2004

The purposes of the study were twofold: to investigate the stereotype of position and direction that the users expect when operating the handles of a water faucet in different directions, and to collect information about user’s preferred directions. Six hundred subjects, aged from teens to over sixties, participated in the experiment with the procedure of showing them actual water faucets of a lever-type handle and two round-shaped handles mounted on the sink(horizontal plane) and wall(vertical plane). The water faucets presented to the subjects were most widely used devices in our living environment. The results showed that when the handle of the lever-type water faucet was in the 'up' position, 63% of the subjects expected the device was 'open'. When the cold hot separated water faucets were mounted on the horizontal or vertical plane, over 50% of those who answered the 'open' direction of round type handles responded as 'counter clockwise' for a 'hot' water faucet and 'clockwise' for a 'cold' water faucet. In conclusion, this study suggests that water faucet devices be designed and installed in the way that the users expect them to operate.

• 공업화학
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• 제10권4호
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• pp.531-536
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• 1999

누출시험 장치를 이용하여 미량 물 누출 실험을 수행하였다. 2.25Cr-1Mo 시편의 누출경로는 나트륨-물 반응 생성물에 의해 plugging되는 경우가 발생하였으나, 대부분 re-open상태를 나타내었다. 또한 누출 경로가 완전 re-open된 후 나트륨 부위에서 시편의 self-wastage pattern은 온도에 영향을 받지 않음을 알 수 있었으며, 누출경로가 re-open 되면서 나타나는 defected 크기는 대략 5 mm 이내임을 알 수 있었다. 누출 경로가 완전 re-open 되는데 걸리는 시간은나트륨 온도가 높을수록 짧게 나타났으며, 평균적으로 $450^{\circ}C$에서 143분, $475^{\circ}C$의 경우 40.7분, $510^{\circ}C$의 경우 34.7분을 나타내었다.

• 물과 미래
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• 제10권2호
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• pp.61-65
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• 1977