• 한국안전학회지
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• 제37권4호
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• pp.113-119
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• 2022

Sudden intrusion of a large amount of surface water into a flood defensive tunnel or pipeline system can compress the residual air. The compressed air may explode along with water through the inlet or air vent, resulting in hydraulic capacity degradation or safety hazards. This study aims to investigate the behavior of compressed air body in pipelines according to the residual air condition with a series of laboratory experiments measuring pressure variation. It has been found that flow characteristics and residual air conditions have a dominant influence on the magnitude and periodicity of the pressure variation. A proper measure to effectively control the residual air is required for securing the design capacity of flood defensive pipeline systems, since the peak pressure is predominantly affected by residual air conditions.

• 수산해양기술연구
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• 제57권3호
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• pp.214-227
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• 2021

The distribution of tidal current and tidal induced residual current, topographical eddies and tidal residual circulation in the waters surrounding the Geumo Island-An Island channel were identified through numerical model experiments and vorticity balance analysis. Tidal current flows southwest at flood and northeast at ebb along the channel. The maximum flow velocity was about 100-150 cm/s in neap and spring tide. During the flood current in the neap tide, clockwise small eddies were formed in the waters west of Sobu Island and southwest of Daebu Island, and a more grown eddy was formed in the southern waters of Geumo Island in the spring tide. A small eddy that existed in the western waters of Chosam Island during the ebb in neap tide appeared to be a more grown topographical eddy in the northeastern waters of Chosam Island in spring tide. Tidal ellipses were generally reciprocating and were almost straight in the channel. These topographical eddies are made of vorticity caused by coastal friction when tidal flow passes through the channel. They gradually grow in size as they are transported and accumulated at the end of the channel. When the current becomes stronger, the topographic eddies move, settle, spread to the outer sea and grow as a counterclockwise or clockwise tidal residual circulation depending on the surrounding terrain. In the waters surrounding the channel, there were counterclockwise small tidal residual circulations in the central part of the channel, clockwise from the northeast end of the channel to northwest inner bay of An Island, and clockwise and counterclockwise between Daebu Island and An Island. The circulation flow rate was up to 20-30 cm/s. In the future, it is necessary to conduct an experimental study to understand the growth process of the tidal residual circulation in more detail due to the convergence and divergence of seawater around the channel.

• 한국환경과학회지
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• 제11권1호
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• pp.41-56
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• 2002

In order to estimate the quantitative roles of the tide induced residual currents, density currents and wind driven currents on the residual currents in Kwangynag Bay Korea, numerical experiments with a diagnostic multi-level model were carried out. Density currents were calculated from the temperature and salinity data observed in January, May, August and November 1998. Anti-clockwise circulations are formed at the western inner part of the bay, the location from the east of Myodo Is. to the south of POSCO Co. and the place between Yeosu peninsula and Namhae Is. from the calculation results of the tide induced residual currents. Velocities of the density currents are less than 3cm/s at the western inner part of the bay and about 5cm/s at the southern entrance of the bay. Density currents get strong in summer and weak in autumn. Wind driven currents at the surface layer flow in the directions of the given winds which are the daily mean winds when the temperature and salinity observations are carried out. In the middle and lower layers, however the wind driven currents flow in the opposite direction to the surface currents as supplementary currents. The surface wind driven currents are greater than the tide induced residual currents or the density currents. The calculated residual currents including the tide induced residual currents, density currents and wind driven currents agree with the results of the current observations approximately. In the Bay, the wind driven currents affect on the residual currents greatestly and tide induced residual currents and density currents do in the second place and the third place.

• 한국수자원학회논문집
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• 제34권6호
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• pp.725-733
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• 2001

본 연구에서는 모형배수지를 이용하여 유출량의 변동여부와 도류벽의 설치여부에 따른 유출수의 잔류염소농도의 변화를 추적하였다. 모형배수지의 실험결과를 고찰해 보면, 유출량을 변동시킨 경우에 있어서 도류벽이 없을 때와 도류벽이 2개 있을 때, 유출수의 평균 잔류염소농도의 차이가 유출량을 일정하게 유지한 경우에 비하여 줄어 들었다. 이는 유출량 변동의 영향에 의한 것으로 유출량의 변동이 심한 배수지에 있어서는 유출량의 변동이 심하지 않은 정수지에서 보다는 도류벽 설치의 효과가 작은 것으로 판단된다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.47-53
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• 2000

Saemangeum coastal area is being constructed the 33km sea dike and 40,000ha reclamation area. The purpose of this study is to find the residual circulations in spring before and after the dike construction by a robust diagnostic and prognostic numerical model. Heat flux at the sea surface in May was adopted on the basis of the daily inflow of solar radiation at the earth surface, assuming an average atmospheric transmission and no clouds, as a function of latitude and time of year(George L.P.,J. E. William,1990). The discharge from the Geum, the Mankyung and the Dongjin rivers was adopted on the basis of experience formula of river flow in May(The M. of C.,Korea, 1993). Water temperature and salinity along the open boundaries are obtained from the results of field observations. The results of spring of the residual flow in the Saemangeum coastal area by a prognostic numerical model lead to the following conclusions: Water temperature in spring is the highest, salinity is the lowest and density is the lowest at the upper layer near the coast after the dike construction. The flow pattern at the upper layer during spring is anti-clockwise circulation between Wi and Shinsi islands. The flow pattern at the lower layer is clockwise circulation between Wi and Shinsi islands.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1597-1602
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• 2003

Numerical analysis is carried out to assess the temperature distribution on the mixing tee line of Residual Heat Removal System (RHRS). In RHRS, hot and cold fluids of main and bypass piping are mixed and unmixed by the flow rate or piping layout. Thermal stratification phenomenon is a cause of major degradation on RHRS piping. According to the analysis for each operation modes, maximum temperature difference between top and bottom of piping were evaluated about 60K when the flow rate of main and bypass lines is same. Temperature difference will be decreased at the elbow on RHRS piping if the length of vertical piping is increased.

• 한국해양학회지:바다
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• 제8권2호
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• pp.164-176
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• 2003

하계 진동만에서 얻어진 영양염 DIN(dissolved inorganic nitrogen) 및 DIP(dissolved inorganic phosphate)의 분포는 이들 농도가 만안쪽에서 매우 높은 것이 특징이다. 또 표층(0∼1 m)과 저층(8 m∼bottom)은 만 안쪽이 고농도 이고 중층(1∼8 m)은 상대적으로 낮다. 이러한 영양염의 분포특성을 바람, 조류, 밀도의 수평경도력 및 잔차류를 고려한 생태계모델을 이용하여 조사하였다. 수치실험은 이들 조건들이 영양염에 각기 어떻게 영향을 미치는 가에 주목하여 실시되었다 조석잔차류를 고려한 경우는 전반적으로 관측값보다 저농도의 분포를 보였고, 바람, 조석잔차류 및 밀도의 수평경도력에 의한 효과를 포함한 경우는 보다 관측값에 근접한 결과를 얻었다 이러한 결과는 통계적 분석 방법에서도 잘 뒤받침된다. 본 연구결과는 하계 진동만에서 영양염의 분포변동에 조류효과 뿐만이 아니라 바람에 의한 취송류 및 밀도의 수평경도력에 의해 발생하는 밀도류의 효과가 매우 중요함을 시사한다.

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1617-1628
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• 2017

In the passive residual heat removal system of a molten salt reactor, one of the residual heat removal methods is to use the thimble-type heat transfer elements of the drain salt tank to remove the residual heat of fuel salts. An experimental loop is designed and built with a single heat transfer element to analyze the heat transfer and flow characteristics. In this research, the influence of the size of a three-layer thimble-type heat transfer element on the heat transfer rate is analyzed. Two methods are used to obtain the heat transfer rate, and a difference of results between methods is approximately 5%. The gas gap width between the thimble and the bayonet has a large effect on the heat transfer rate. As the gas gap width increases from 1.0 mm to 11.0 mm, the heat transfer rate decreases from 5.2 kW to 1.6 kW. In addition, a natural circulation startup process is described in this paper. Finally, flashing natural circulation instability has been observed in this thimble-type heat transfer element.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.106-111
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• 2000

The residual stresses in molded plastic parts can be divided into the flow induced residual stresses produced in flowing stages and the thermally induced residual stresses produced in cooling state. Reducing residual stresses in the final parts is one of the goals in recent study. The present study focused on comparing the predicted values for thermal residual stresses in freely and constrained quenched plastic plates with and without free volume theory. As a result the final residual stresses showed the opposite pattern in thickness direction. furthermore by applying free volume theory the predicted residual stress at the center showed about 50% of the values without free volume theory for constrained quenched case.

• 한국해양학회지
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• 제22권1호
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• pp.9-18
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• 1987

제주도 주변 해역에 대한 많은 해수 특성 연구와 최근의 해류 관측 결과들은 제주도 서쪽 및 북쪽 해안에 연중 존재하는 시계 방향의 잔류가 있 음을 시사해 준 다. 제주도 동편 해역에서는 쓰시마 해류가 북쪽과 북동쪽으로 흐른다. 이 논문에서 는 2차원 비선형 천해방정식의 수치해로부터 구한 제주도 주변의 조석 잔차류가 관 측된 잔류를 어떻게 설명할 수 있는 가를 고찰하였다. 계산된 조석 잔차류는 섬 주 위에서 우선 회순환을 나타내며 섬 주위의 해저 경사 위에서만 2-4cm.s$^{-1}$의 크기로 현저히 나타나고 섬에서 멀리 떨어진 외해에서는 무시할 정도로 작다. 또한 제주도 주변의 잔류 순환에 대한 쓰시마 해류의 영향을 보기 위해 모델에 항류를 도입하여 수치 실험을 시도 하였다. 이러한 수치 실험 결과, 조석 잔차류와 쓰시마 해류에 기인된 항류의 복합된 효과가 제주도 서쪽 및 북쪽 해안에서 관측된 우선회 잔류와 섬의 동쪽 해역의 북향류를 잘 설명할 수 있음이 밝혀졌다.