• Nuclear Engineering and Technology
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• 제27권6호
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• pp.888-893
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• 1995

맨봉 배열에 의해 형성되는 부수로를 흐르는 난류 유동장의 구조는 피치 대 봉직경의 비에 따라 변하게 된다. 피치 대 봉직경 비가 큰 경우에는 난류 응력 분포가 관 유동의 분포와 유사하다 그러나 피치 대 봉직경 비가 작은 경우에는 특히 간극 영역에서 난류 특성이 관 유동의 분포와는 달라진다. 완전히 발달된 맨봉 주위의 난류 유동장에서 난류응력과 난류운동에너지 사이의 선형 관계가 개발되었다. 개발된 상관 관계식은 난류 연구에 응용되는 여러 이론적 분석에 연관지어 사용될 수 있다.

• 한국조경학회지
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• 제32권2호
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• pp.78-85
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• 2004

To manage rainwater environmentally friendly, it is necessary to let the rainwater be infiltrated naturally and make reservoirs to detain it in the chosen spot. Not only should it be prepared to handle the city flood, but also it be a necessary alternative for establishing the ecological water circular system in cities. Therefore, considering the present rainwater. management system, this study analysed the status of products which can be interchanged from existent systems to rainwater infiltrating systems. In this study, the infiltrating equipment that is applicable to the Korean drainage system was developed. The case was studied out to investigate the effects of infiltrating and the detaining ability of the developed product. The case site, block 6 of Sang-am residence, was selected and analyzed. The amount of infiltration and detention per unit of the introduced facilities, i.e., infiltrating pipes and tanks were calculated. In this research, the amount of each infiltrating tank was revealed to be 1.353 m/hr and the amount of detention as 0.299 m/hr. And the amount of each infiltrating pipe was found to be 0.541 m/hr and the amount of detention was 0.118 m/hr. To examine the effects of the system, the total amount of the outlet before and after installing was compared and calculated. In doing this, a basis for deciding the arrangement and number of tanks and pipes of the infiltrating system was made.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2000년도 학술대회지
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• pp.255-266
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• 2000

Since 1993, Seohae grand bridge has been continued construction for 7 years and will be completed late this year. The bridge is a part of west sea castal highway and consists of 3 types of bridge including precast segmental method, free cantilever method and cable stayed bridge. A cable stayed bridge is the core of this bridge and it consists of 5 span, symetrical cable-stayed bridge with a total length of 990 m. The main span between two H-shaped pylons extending approximately 180 M above massive foundation of a cable stayed bridge is 470 m long and an approach span of that is 260 m long respectively. The circular cofferdam with 16 ea of 25 m diameter flat type sheet pile had been applied to construct foundation. The slipform method had been applied for forming of con'c of two H-shaped pylons with 3 cross beams respectively which is varied horizontally and vertically. The deck has been erected with balanced cantilever method using movable derrick crane. The stay cables is a bundle of parallel individually protected, 7 wire high tensile strands. The strands is hot deep galvanized and sheathed with a tight high density polyethylene coating. A petroleum wax fills all the inter-wire voids. The bundle of strands to prevent from deterioration due to the ambient problem covered with high density polyethylene pipe. The Isotension method has been applied for the stressing of cable strands to ensure uniformity of force in all the strands of a syay and such works has been performed on the stay specially provided in the pylon.

• 대한의용생체공학회:의공학회지
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• 제11권2호
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• pp.233-242
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• 1990

In the current flow visualization studies, the role of non-Newtonian characteristics (such as shearra to dependent viscosity and viscoelasticity ) on flow behavior across the sudden ex- pansion step in a circular pipe as a model for blood flow experiments is investigated over a wide range of Reynolds numbers. The expansion ratios tested are 2.000 and 2.667 and the range of the Reynolds number covered in the current flow visualization tests are 10~35, 000 based on the inlet. diameter. The reattachment longuEs for the viscoelastic fluids in the lami- nar flow regime are found to be much shorter than those for the Newtonian fluid. In addition it decreases significantly with increasing concentration of viscoelastic fluids at the same Reynolds number. However, in the turbulent flow regime, the reattachment length for the viscoelastic fluids Is two or three times longer than those for water, and gradually increases with increasing concentration of viscoelastic solutions, resulting In 25 and 28 step-height dis- tances for 500 and 1, 000 lpm ployacrylamide solutions, respectively. This may be due to the fact that the elasticity in pobacrylamide solutions suppresses the eddy motion and controls separation and reattachment behavior in the sudden expansion pips flow.

• 대한조선학회논문집
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• 제48권3호
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• pp.260-266
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• 2011

For long slender offshore structures, such as cables and pipe lines, their interaction with surrounding fluid flow becomes an important issue for global design of ocean systems. We employ a long circular cylinder as a representative case of slender offshore structure. A flexibly mounted cylinder in cross-flow generates complex vortex shedding and results in oscillation of the structure. In this paper, flow behind a circular cylinder at Re=100 is simulated. The vortex shedding pattern and flow induced motion are examined in the cross flow configuration as well as with various yaw-angled configurations. The "Lock-in" phenomenon is also observed when reduced velocity is approximately 4.0. The MAC Grid system, which is the typical grid system for Cartesian mesh and pressure correction methods, are used for solving the incompressible Navier-Stokes equations. Predictor/Corrector method is applied for obtaining a non-linear response of structure at the flexibly mounted. The existance and motion of the body is represented by the immersed boundary technique.

• 자원환경지질
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• 제18권4호
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• pp.357-368
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• 1985

경주(慶州) 남부(南部) 2.8km 지점에는 치술령 화산암층이 분포하며, 이 화산암층 보다 후기에 분출 형성된 distreme이 있다. diatreme은 지름이 1.2km의 원형의 화구로서 화산쇄설물로 충진 되어 있다. 이 화산 쇄설물은 proximal ballistic fall deposits로서 층리를 보여주며, 각 층은 상당히 두껍고 특징적으로 많은 양의 accretionary lapilli가 함유되어 있다. 이러한 특징은 시추에 의해 지표 하부 650m가지 확인되었다. 이러한 특징으로 보아 diatreme은 규장질 magma에 많은 양의 물이 유입되는 환경에서 연속인 분출 활동을 하였음을 의미하고, 화산 활동 기간 중에 연속적으로 화산쇄설물이 퇴적 및 침강 하였음을 의미한다.

• 설비공학논문집
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• 제14권6호
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• pp.441-449
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• 2002

Single-phase convection and partial nucleate boiling in free-surface and submerged jet impingements of subcooled water ejected through a 2-mm-diameter circular pipe nozzle were investigated by local measurements. Effects of jet velocity and nozzle-to-imping-ing surface distance as well as heat flux on distributions of wall temperature and heat transfer coefficients were considered. Incipience of boiling began from far downstream in contrast with the cases of the planar water jets of high Reynolds numbers. Heat flux increase and velocity decrease reduced the temperature difference between stagnation and far downstream regions with the increasing influence of boiling in partial boiling regime. The chance in nozzle-to-impinging surface distance from H/d=1 to 12 had a significant effect on heat transfer around the stagnation point of the submerged jet, but not for the free-surface jet. The submerged jet provided the lower cooling performance than the free-surface jet due to the entrainment of the pool fluid of which temperature increased.

• 에너지공학
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• 제13권4호
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• pp.275-280
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• 2004

관내부로 흐르는 물에 초음파 진동을 가진 하였을 때 관내 열전달이 증진되는 효과를 실험 및 수치해석을 통해 연구하였다 원형관 벽면에서 관내부로 흐르는 물로의 대류 열 전달계수를 초음파 진동이 있을 때 와 없을 때에 측정하였다. 이 결과를 비교함으로써 초음파진동이 전열성능 향상에 미치는 영향을 정량화 하였다. 이러한 현상에 영향을 줄 수 있는 유량과 온도의 범위를 넓히기 위하여 수치해석을 수행하였다. FLUENT 6.1을 이용하여 관내의 유동장과 온도분포를 해석하고 초음파 진동 유무 시 대류 열 전달계수를 평가하였다 연구결과 초음파진동이 강제대류 조건에서 전열성능을 향상시키며 그 영향은 관내를 흐르는 물의 유량에 따라 크게 변한다는 것을 보여주고 있다.

• 한국기계가공학회지
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• 제20권7호
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• pp.25-32
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• 2021

In the previous study, a study was conducted to improve the exhaust gas intake efficiency by improving the existing soot measurement probe in the shape and angle of the exhaust port. As a result, it can be seen that the smoke measurement performance according to the shape and angle is improved. In previous studies, the performance of the soot probe was not confirmed for the Korean KD 147 mode, which has a low suction flow rate and a long inspection time. So, we would like to confirm the improvement of the smoke probe performance of the Korean KD 147 mode, which is close to the actual driving conditions. The probe used in this study is another type of probe, and has a circular ring shape instead of a rib and variable center position unit, so the probe center hole is located close to the center of the exhaust pipe.

• 한국산학기술학회논문지
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• 제16권3호
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• pp.2242-2248
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• 2015

본 연구는 폭설로 인하여 비닐하우스가 붕괴되는 사고가 잇따르는 것에 대비하여 효율적인 비닐하우스 골조의 개선방안을 찾고자 진행되었다. 2013년 겨울, 비닐하우스 피해가 가장 컸던 곳은 경북과 강원도로, 이 지역에서 가장 많이 사용되고 있는 비닐하우스 유형(07-단동 3형, 07-단동 18형)에 대하여 최대 적설량 대비 30%까지 하중을 증가시켜 MIDAS GEN 프로그램을 사용하여 구조적 안전성을 검토하였다. 해석의 결과, 경주의 비닐하우스는 적설하중의 중가에 대해 안전하였으나 속초의 경우는 위험요인이 발생하였으며, 강릉의 비닐하우스는 기존 적설하중에서도 붕괴 가능성이 있는 것으로 나타났다. 폭설에 대비, 비닐하우스 구조단면의 성능을 개선하기 위하여 서까래를 이루는 원형파이프 단면의 성능을 개선하는 동시에 서까래의 간격을 증가시켜 적정 비닐하우스 구조를 검토한 결과, 서까래의 관경과 간격을 증가시키는 방안이 서까래의 두께와 간격을 증가시키는 방안보다 구조적으로 효율적인 것으로 해석되었다. 향후 폭설에 대비하여 비닐하우스의 서까래 관경을 증가시킨 적정 규격의 제안이 필요할 것으로 판단된다.