• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.425-432
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• 2002

Both numerical and experimental studies on sedimentation efficiency of a sedimentation bed were carried out. Three different structures of sedimentation bed and five different combinations of blockage ratio of center feed wall and angle of distributor are implemented to find the optimal values of geometric parameters. The effect of rotation of the distributor on sedimentation efficiency is also investigated. It reveals that the effect of blockage ratio and angle of distributor on sedimentation efficiency is considerable, while rotation effect can be neglected, and that calculated efficiencies show good agreements with those of experiment, qualitatively.

• 한국유체기계학회 논문집
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• 제6권2호
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• pp.54-61
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• 2003

Both numerical and experimental studies on the sedimentation efficiency of a sedimentation bed were carried out. Three different structures of sedimentation bed and five different combinations of blockage ratio of center feed wall and angle of distributor are implemented to find the optimal values of geometric parameters. The effect of rotation of the distributor on sedimentation efficiency is also investigated. It reveals that the effects of blockage ratio and angle of distributor on sedimentation efficiency are considerable, while rotation effect can be neglected, and that calculated efficiencies show good agreements with those of experiment, qualitatively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.95-98
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• 2002

Three-dimensional flow analyses for two different ratios of radius to height of sedimentation bed are implemented to evaluate the effect of blockage ratio of center feed wall and angle of distributor on sedimentation efficiency, and to find the optimal value of those parameters. Sedimentation efficiencies for three different shapes are compared with and without rotation speed. And then, five different combinations of blockage ratio of center feed wall and angle of distributor are compared It reveals that the effect of blockage ratio of center fled wall and angle of distributor is considerable to sedimentation efficiency while rotation effect can be neglected and $0.55 and 33^{\circ}$for blockage ratio of center food wall and angle of distributor, respectively, ive the best sedimentation efficiency.

• Journal of Advanced Research in Ocean Engineering
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• 제2권3호
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• pp.99-111
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• 2016

Seabed affected by scouring, sedimentation, and siltation occurrences often cause exposure, which induces risks to existing structures or crude oil or gas pipeline buried subsea. In order to prevent possible risks, more economical structure installation methodology is proposed in this study by predicting and managing the risk. Also, the seabed does not only consist of sandy material, but clayey soil is also widespread, and the effect of undrained shear strength should be considered, and by cyclic environmental load, pore water pressure will occur in the seabed, which reduces shear strength and allows particles to move easily. Based on previous research regarding sedimentation or erosion, the average value of external environmental loads should be applied; for scouring, a 100-year period of environmental conditions should be applied. Also, sedimentation and erosion are mainly categorized by the bed load and suspended load; also, they are calculated as the sum of bed load and suspended load, which can be obtained from the movement of particles caused by sedimentation or erosion.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.292-295
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• 2001

A Study on the precipitation characteristics of nickel hydroxide as well as carbonate and sulfide is carried out to determine the proper treatment condition of the wastewater induced from nickel-plating industry. The nickel concentrations in the effluent could be kept lower than 5ppm when the value of pH was maintained higher than 10. The precipitation of nickel salts by alkaline addition to the nickel containing model wastewater was conducted by using proper amount of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium sulfide. In case of the sulfide treatment, the residual nickel concentration in the clear water after precipitates removed showed the lowest value. The influences of the precipitation condition upon the particle size of the crystals precipitated were also investigated. In spite of the various precipitation conditions were adopted, the particle size of the precipitated crystals showed no great differences. The sedimentation rates of the precipitated particle bed were observed and the free sedimentation period was terminated within 20 minutes. Although the hindered sedimentation as well as bed compaction progressed subsequently, the bed heights were maintained almost the same level after two hours of sedimentation.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.457-469
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• 2016

During the late phase of severe accidents of light water reactors, a porous debris bed is expected to develop on the bottom of the flooded reactor cavity after breakup of the melt in water. The geometrical configuration, i.e., internal and external characteristics, of the debris bed is significant for the adequate assessment of the coolability of the relocated corium. The internal structure of a debris bed was investigated experimentally using the DAVINCI (Debris bed research Apparatus for Validation of the bubble-Induced Natural Convection effect Issue) test facility. Particle sedimentation under the influence of a two-phase natural convection flow due to the decay heat in the debris bed was simulated by dropping various sizes of particles into a water vessel with air bubble injection from the bottom. Settled particles were collected and sieved to obtain the particle mass, size distribution in the radial and axial positions, and the bed porosity and permeability. The experimental results showed that the center part of the particle bed tended to have larger particles than the peripheral area. For the axial distribution, the lower layer had a higher fraction of larger particles. As the sedimentation progressed, the size distribution in the upper layers can shift to larger sizes because of the higher vapor generation rate and stronger flow intensity.

• 한국수자원학회논문집
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• 제46권7호
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• pp.707-717
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• 2013

충적하천에서 발생하는 하천의 침식과 퇴적은 흐름을 통해 발생하는 자연적인 현상이다. 침식 및 퇴적과 관련된 수치모형을 이용한 분석은 하천에 존재하는 보와 같은 수리구조물들의 유사이송을 연구하는데 중요한 요소이다. 본 연구에서는 다기능보들의 효과적인 운영을 위하여 낙동강수계에 위치해 있는 창녕함안보를 대상으로 하상변동을 예측하였다. 2차원 모형은 CCHE2D를 이용하여 유사이송이 지배적으로 발생하는 다기능보 상 하류 구간 12 km를 대상으로 침식과 퇴적에 대한 모의를 수행하였다. 2003년 태풍 "매미"사상을 대상으로 모형을 검 보정 하였으며, 모의결과와 관측값의 비교를 통하여 전체 모의구간에서 신뢰성 있는 결과가 도출되었다. 함안창녕보가 건설된 이후 태풍사상에 의한 하상변동은 상당히 증가하는 것으로 나타났고 하상변동은 유사의 재분배를 야기하였다. 보와 같은 수리구조물들은 하도내 흐름과 유속을 변화시키기 때문에 세굴과 퇴적 문제를 심화시켰다.

• 한국수자원학회논문집
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• 제45권2호
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• pp.217-227
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• 2012

본 논문에서는 저수지 퇴사 및 배사현상을 모의하기 위한 준정류 모형을 제시하였다. 준정류 모형은 하상은 시간에 따라 변하지만 유동은 정상류라는 가정에 기초한다. 이것은 유동에 비해 매우 장기간에 걸쳐 하도형태가 변하기 때문에 타당하다. 개발된 모형을 저수지 퇴사에 관한 실내실험에 적용하였다. 수치계산을 통하여 상류측에서 공급되는 유사량에 따라 하도의 수심 및 하상경사가 조정되는 것을 보였다. 수치모의에 의한 수위와 하상고가 실험결과와 잘 일치하는 것을 확인하였다. 또한, 모형을 저수지 배사 현상에 관한 선행 실험 조건에 적용하였다. 이 경우에는 배사를 촉진시키기 위해 실험에서 부정류를 발생시켰기 때문에 준정류 모형에 의한 모의결과가 관측자료와 잘 일치하지 않는 것을 확인하였다. 마지막으로, 유사공급에 따른 평형 수심과 하상경사에 관한 공식을 제시하였으며 수치실험을 통하여 이를 검증하였다.

• 한국수자원학회논문집
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• 제44권1호
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• pp.31-40
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• 2011

본 연구에서는 2차원 하상변동 수치모형인 CCHE2D 모형을 이용하여 낙동강하구둑에서의 퇴사저감 방안을 분석하였 다. 현재 매년 시행되고 있는 준설방법에 대한 효과를 정량적으로 분석하였으며 준설방법을 대체할 수 있는 퇴사저감 방법으로 하폭축소를 통한 퇴사저감 방안에 대해 모의를 수행하였다. 분석에 사용된 모형은 각각 유사량 공식과 유사이송 형태에 대해 모형 검보정을 수행하였으며 낙동강하국둑의 경우 Ackers and White (1973) 공식과 소류사 형태의 유사이송 방식을 수치모의 시 사용하는 것이 실제 하상변동 결과와 가장 유사한 것으로 나타났다. 검보정된 CCHE2D 모형을 이용하여 현재 시행되고 있는 준설방법에 대한 분석을 수행하였으며 그 결과, 준설이 수행된 구간에서 평균 0.2m의 퇴적량 감소를 확인할 수 있었다. 또한, 하폭축소를 통한 퇴사저감 분석 결과, 평균 0.4m의 퇴사저감 효과가 있는 것으로 나타났으며 특히 하폭이 축소된 구간에서는 축소전과 비교해 최대 2.0m 정도의 퇴사저감 효과가 있는 것으로 분석되었다.

• 토지주택연구
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• 제8권3호
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• pp.161-169
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• 2017

In this study, sediment transfer and precipitation analysis of the test bed watershed was conducted through the model for the application and practical use of the urban sediment disaster prevention technology, and used this as an aid to design to secure reliability. In addition, conducted the test bed monitoring with the defense technology, analyzed the effect, and established the maintenance plan. Analyzed the change of soil deposition volume through arbitrary slope adjustment for the currently installed stormwater conduit of the test bed watershed. As a result, it is important to reduce the total sedimentation amount in the adjustment of the slope of the entire pipeline, but it is important that the sedimentation depth of each sediment does not rise to such a degree as to threaten the performance of the pipeline. Considering these matters, it is necessary to design the pipeline to prevent the clogging of the soil from the viewpoint of the reliability of the entire pipeline. The sediment disaster defense technology test bed is divided into a new city and an old city, and old city test bed is under construction. The result obtained through the monitoring of the test bed in the new city, sediment disasters such as debris can delay the time to reach the downtown area, and it is possible to secure the golden time, such as evacuation and rescue through the warning system. Also, the maintenance of the test bed application was suggested. Continuous and systematic monitoring is required for securing the reliability of element technology and successful commercialization.