• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2015년도 학술발표회
• /
• pp.240-240
• /
• 2015

As Simpson et al. (1990) emphasized the importance of the straining process in the stratification and mixing in the estuarine circulation process, various researches have investigated on the relative contribution of each process to the overall potential energy anomaly dynamics. However, many numerical works have done only for two dimensional modeling along channel or the short distance cross sectional three dimensional simulations as Burchard et al. (2008) and the estuarine channel was not simulated so far. But, in the study on the physics of shallow coastal seas, spatial dimension in the three dimensional way affects significantly on results of a particular numerical model. Therefore, the comparison of two and three dimensional models is important to understand the real physics of mixing and stratification in an estuary. Also, as Geyer and MacCready (2013) pointed out that the lateral process seems to be important in determining the periodic stratifications, to study such process the three dimensional modeling must be required. The present study uses a numerical model to show the signification roles of each term of the time-dependent dynamic equation for the potential energy anomaly (PEA) in controlling along and lateral channel flows and different stratification structures. Moreover, we present the relationships between the ${\Phi}$-advection, the depth mean straining, vertical mixing and vertical advection can explain well how water level, salinity distribution and across velocity 2D model are slightly different from 3D.

• 한국연소학회지
• /
• 제3권1호
• /
• pp.41-48
• /
• 1998

A numerical study on combustion in a fluidized bed is based on three dimensional mixing and dispersion phenomena in the bed owing to the bubble growth in the vertical direction. As fluidizing velocities increase, bubble diameters increase, which activates the fuel dispersion in the bed. The combustion rates, however, reduce due to the decrease of gas exchange rates between bubble and emulsion phases. Fuel distributions in the bed are dependent on fluidizing velocities, equivalence ratios, fuel particle diameters, fuel feeding points, and the number of fuel feeders.

• 산업기술연구
• /
• 제31권B호
• /
• pp.81-90
• /
• 2011

Centrifuge modeling and numerical analysis on works of breakwater construction were performed to investigate the behavior of caisson type of breakwater and foundation treated with the method of DCM (Deep Cement Mixing) under the condition of wave action in field. In centrifuge modeling, construction sequence of breakwater caisson such as preparation of ground, treatment of DCM, installation of rubble mound, placement of breakwater caisson and lateral loading on the breakwater due to wave action were reconstructed. Lateral movement of model breakwater and ground reaction in the vertical direction were monitored during test. Stress concentration ratio between the untreated ground and the treated ground with DCM was evaluated from measurement of vertical stresses on each ground. Numerical analysis with the software of PLAXIS was carried to compare with Results of centrifuge model test. It was found that stability of model breakwater was maintained during stage of construction and the compared results about stress concentration ratio were in relatively good agreements.

• 한국대기환경학회지
• /
• 제14권4호
• /
• pp.321-332
• /
• 1998

Various meleorologlcal dada obtained by SODAR system in shoreline area surrounding Boryung power plant have been analysed to investigate atmospheric diffusibility. Important conclusion may be summarized as follows; (i) Stability classification scheme based on co (standard deviation of wind direction in degree for averaging time of 1 hour) appears to evaluate certain atmospheric velocity and : indicate horizontal mean wind speed. Thus different scheme for stability classification seems to be preferable in order to appropriately estimate lateral and vertical dispersion coefficients cy and cz, respectively. (ii) As a result of comparisons between 3 available schemes for estimating of mixing height, best one turned out to be the double height scheme where height corresponds to maximum cw.

• 한국수자원학회논문집
• /
• 제32권2호
• /
• pp.153-162
• /
• 1999

본 연구에서는 정지수체에서 다공확산관을 통해 방류된 연직다중의 혼합 및 희석 특성에 대해 규명하였다. 3차원 실험수조에서 실험을 통해 밝혀진 결과는 다음과 같다. 우선 다공확산관의 병합과정을 살펴보면 흐름의 안정조건에 따라 병합거리가 다소 차이가 있기는 하지만 {{{{ { z}_{ } }}}}/{{{{ {l}_{ } }}}}가 대략 3인 지점부터 병합이 시작되어 그 이후에는 평면부력？의 거동에 서서히 가까워짐을 알 수 있다. 최소희석률에 대해 분석해 본 결과, 방류운동량이 지배적인 영역, 천이영역, 그리고 부력이 지배적인 부력류영역으로 나누어 희석률 특성을 표현할 수 있음을 알 수 있었다. 본 연구의 실험결과 다공확산관의 경우 부력류영역의 희석률 상수가 평면확산관에 비해 15% 더 높게 나왔다. 그 이유는 다공확산관의 경우 병합 이전에는 개별의 경계면에서 주변수의 포획이 발생하여 희석이 증대되기 때문이다.

• 한국지반신소재학회논문집
• /
• 제15권3호
• /
• pp.27-37
• /
• 2016

국내 GCP공법은 많은 선행연구가 진행되었으나, 설계자의 경험에 의해 의존하여 설계되고 있는 실정이므로 파괴사례가 종종 보고되고 있다. 이에 따라 명확한 파괴 원인규명 및 파괴예방대책 수립이 어려운 실정이다. 따라서 본 연구에서는 GCP공법의 합리적인 설계법의 제안을 위한 기초단계로써, GCP에 사용되는 최적배합비를 대형직접전단시험을 통해 결정하고, 내부마찰각의 변화에 따른 응력분담비의 변화 및 지반의 수직/수평 침하거동을 수치해석을 통하여 분석하였다. 직접전단 실험결과 쇄석과 모래의 최적배합비는 70:30으로 평가되었다. 수치해석결과 내부마찰각이 증가할수록 응력분담비가 증가하나 일정한 값으로 수렴하고 침하량이 감소하며, 최적배합비로 시공할 경우 측방유동 및 히빙현상의 감소를 유도할 것으로 판단된다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.1803-1806
• /
• 2007

The General roles of a spacer grid(SG) are providing a lateral and vertical support for fuel rods, promoting a mixing of coolant and keeping guide tubes straight so as not to impede a control rod insertion under any normal or accidental conditions. To evaluate the impact characteristics of a SG such as impact velocity, critical buckling strength and duration time, a few types of impact tests for SGs have been conducted. In a previous study, a new welding method, a through-welding method, was proposed to increase critical buckling strength of a SG without any design change or material change and was verified by impact tests with $7{\times}7$ partial SG specimens.In this paper, the effect of through-welding method in case of a $16{\times}16$ full-size SG is investigated by pendulum impact tests with $16{\times}16$ SG specimens. And the increase of critical buckling strength for full-size SGs is measured by comparison with impact results of spot-welded and through-welded SGs.

• 한국해안해양공학회지
• /
• 제6권4호
• /
• pp.413-420
• /
• 1994

하천수 플룸(plume)의 퍼짐을 다루는 역학은 플룸의 경계면이 시간과 공간에 따라서 변하기 때문에 자유경계조건의 문제(free boundary problem)로 다루어야 하는 대단히 복잡한 비선형 문제이다. 더욱이 플룸경계를 통한 주변수의 혼합까지 고려할 경우 그 복잡성은 한층 더해진다. 이러한 비선형성과 복잡성을 피하는 기법의 하나가 적분해석법인 바, 본 논문에서는 하천수 플룸의 흐름축에 수직한 횡방향 및 수심방향에 대하여 기본방정식들을 적분함으로 3차원 문제를 1차원 문제로 치환하는 적분해석법을 사용하였다. 다만 이 일이 가능하기 위해서는 유동변수들(유속, 밀도 등)의 횡방향 및 수심방향의 분포함수가 알려져 있음이 전제되어야 하는데 유속의 축방향성분 및 플룸과 주변수 간의 밀도차가 상기 두 방향에 대해서 가우스(Gauss)분포를 갖는다는 잘 검증된 가정을 활용하였다. 그리고 이 가정에서 플룸의 횡방향 유속을 도출해낸 본 연구자들의 기발표된 논문의 결과도 활용하였다. 결과로 얻어진 연행(entrainment)효과까지 포함한 방정식들을 Runge-Kutta 수치해석법을 사용하여 풀었다. 그리하여 하천수 풀룸의 3차원적 해석을 쉽게 수행할 수 있는 수치해석기법을 얻어냈다.

• 한국물환경학회지
• /
• 제34권4호
• /
• pp.363-374
• /
• 2018

The Han River serves as an important water resource for the city of Seoul, Korea and in the neighboring metropolitan areas. From the Paldang dam to the Jamsil submerged weir, the 4 water intake stations that are located for the Seoul metropolitan population were under review in this study. Therefore the water quality management in this section is very important to monitor, analyze and review to rule out any safety concerns. In this study, a 3-D hydrodynamic model, EFDC (Environmental Fluid Dynamics Code), was applied to the downstream of the Paldang Dam in the Han River, which is about 23 km in length, to determine issues related to water resource management. The 3-D grid was composed of 2,168 horizontal grids and three vertical layers. In this case, the hydrodynamic model was calibrated and verified with an observed average daily water surface elevation, water temperature and flow rate data for 3 years (2013~2015). The developed EFDC model proved to reproduce the hydrodynamics of the Han River well. The composition ratios of the noted incoming flows at the monitored intake stations for 3 years and their flow patterns in the river were analyzed using the validated model. It was found that the flow of the Wangsuk Stream depended on the Paldnag dam discharge, and it was noted that the composition ratios of the stream at the intake stations changed accordingly. In a word, the Wangsuk Stream moved mainly along the right bank of the Han River under the condition of a normal dam flow. As can be seen, when the dam discharge rate was low, the incidence of lateral mixing was often seen. The scenario analyses were also conducted to predict the transport of conservative pollutants as in the case of a chemical spill accident. Generally speaking, when scenarios were applied, the arrival time and concentration of pollutants at each intake station was thus predicted.