• 한국항해학회지
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• 제23권2호
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• pp.29-42
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• 1999

An accurate method of estimating ship maneuverability needs to be developed to evaluate precisely and improve the maneuverability of ships according to the water depth. In order to estimate maneuverability by a mathematical model. The hydrodynamic forces acting on a ship hull and the flow field around the ship in maneuvering motion need to be estimated. The ship speed new the berth is very low and the fluid flow around a ship hull is unsteady. So, the transient fluid motion should be considered to estimate the drag force acting on the ship hull. In the low speed and short time lateral motion, the vorticity is created by the body and grow up in the acceleration stage and the velocity induced by the vorticity affect to the body in deceleration stage. For this kind of problem, CFD is considered as a goof tool to understand the phenomena. In this paper, the 2D CFD code is used for basic consideration of the phenomena to solve the flow in the cross section of the ship considering the ship is slender and the water depth is large enough. The flow fields Added and hydrodynamic forces for the some prescribed motions are computed and compared with the preliminary experiment results. The comparison of the force with measurement is shown a fairly good agreement in tendency. The 3D Potential Calculation based on the Hess & Smith Theory is employed to predict the surge, sway added mass and yaw added moment of inertia of hydrodynamic coefficients for M/V ESSO OSAKA according to the water depth. The results are also compared with experimental data. Finally, the sway added mass of hydrodynamic coefficients for T/S HANNARA is suggested in each water depth.

• 환경영향평가
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• 제32권6호
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• pp.473-487
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• 2023

1970~1980년대 준공된 우리나라의 다목적댐 저수지에는 발전방류를 위한 고정식 취수구가 심층에 설치되어 있어 일부 댐 하류에서는 냉수 방류에 의한 농작물 냉해, 안개 일수 증가 등의 문제점이 제기된 바 있다. 본 연구에서는 고정식 취수구를 통해 심층 취수가 이루어지고 있는 합천호를 대상으로 취수 수심이 저수지의 수온 성층 구조와 방류 수온에 미치는 영향을 분석하였다. 3차원 수리수질모형인 AEM3D를 이용하여 합천호의 연직 수온 분포를 재현하고 계절별 수온성층 구조를 분석하였으며, 수문 조건에 따른 수온성층 변화를 비교 분석하기 위하여 풍수해와 갈수해를 대상으로 모델링 하였다. 또한 취수심 변경 시나리오를 적용함으로써 취수 수심이 수온성층 구조에 미치는 영향을 분석하였다. 모의 결과 심층 취수를 표층 취수로 변경할 경우 수온약층의 형성 위치가 풍수해 6.5 m, 갈수해 6.8 m 감소하여 더 얕은 수심에 형성될 것으로 분석되었다. 또한 수체 안정도 지수인 Schmidt Stability Index (SSI)와 Buoyancy frequency (N²)가 증가하여 수온성층 강도가 증가하는 것으로 나타났다. 표층 취수시 연평균 방류수온이 풍수해 3.5℃, 갈수해 5.0℃ 증가하여 하류하천의 영향은 감소하나, 호내의 저수온층 수체적과 수온성층 강도가 증가하므로 추후 수질관리를 위해 취수심을 댐 운영의 주요인자로 고려해야 할 것으로 판단된다.

• Journal of Construction Engineering and Project Management
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• 제7권1호
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• pp.26-29
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• 2017

This paper represents the experimental investigation of chloride penetration into plain concretes and reinforced concretes. The main objective of this work is to study the main influencing parameters affecting corrosion of steel in concrete. Plain cement concrete and reinforced cement concrete with different water-cement ratios and different cover depth were subjected to ponding test. Ponding of specimens were done for different periods into 10% NaCl solution. Depth of penetration of chloride solution into specimens was measured after ponding. Specimens were crushed and reinforcements were washed using $HNO_3$ solution and weight loss due to corrosion was calculated accordingly. There was a linear relationship between depth of penetration and water-cement ratio. It was also observed that, corrosion of reinforcing steel increases with chloride ponding period and with water-cement ratio. Corrosion of steel in concrete can be minimized by providing good quality concrete and sufficient concrete cover over the reinforcing bars. Water-cement ratio has to be low enough to slow down the penetration of chloride salts into concrete.

• Membrane and Water Treatment
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• 제10권1호
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• pp.67-74
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• 2019

Apparent changes in the natural hydrologic cycle causing more frequent floods in urban areas and surface water quality impairment have led stormwater management solutions towards the use of green and sustainable practices that aims to replicate pre-urbanization hydrology. Among the widely documented applications are infiltration techniques that temporarily store rainfall runoff while promoting evapotranspiration, groundwater recharge through infiltration, and diffuse pollutant reduction. In this study, a laboratory-scale infiltration device was built to be able to observe and determine the factors affecting flow variations and corresponding solids removal through a series of experiments employing semi-synthetic stormwater runoff. Results reveal that runoff and solids reduction is greatly influenced by the infiltration capability of the underlying soil which is also affected by rainfall intensity and the available depth for water storage. For gravel-filled structures, a depth of at least 1 m and subsoil infiltration rates of not more than 200 mm/h are suggested for optimum volume reduction and pollutant removal. Moreover, it was found that the length of the structure is more critical than the depth for applications in low infiltration soils. These findings provide a contribution to existing guidelines and current understanding in design and applicability of infiltration systems.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.265-270
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• 2007

The potential and step voltage distribution around low voltage joint-box cover were simulated with the variation of resistivity of water, depth of submerged water and point of leakage current. The potential distribution is very high gradient around low voltage joint-box, this condition is very dangerous states.

• 한국토양비료학회지
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• 제48권5호
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• pp.522-527
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• 2015

Decision of available soil depth based on soil physical and hydraulic properties for the $3^{rd}$ Landscape Vegetation Project in the Incheon International Airport was attempted. The soil samples were collected from the 8 sites at different depths, 0-20 and 20-60cm, for the three project fields, A, B, and C area. Physical and chemical properties including particle size distribution, organic matter content and electrical conductivity were analyzed. Hydrological properties including bulk density and water holding capacity at different water potential, -6 kPa, -10 kPa, -33 kPa, and -1500 kPa were calculated by SPAW model of Saxton and Rawls (2006), and air entry value was calculated by Campbell model (1985). Based on physical and hydrological limitation, feasibility and design criteria of soil depth for vegetation and landfill were recommended. Since the soil salinity of the soil in area A area was $19.18dS\;m^{-1}$ in top soil and $22.27dS\;m^{-1}$ in deep soil, respectively, landscape vegetation without amendment would not be possible on this area. Available soil depth required for vegetation was 2.51 m that would secure root zone water holding capacity, capillary fringe, and porosity. Available soil depth required for landscape vegetation of the B area soil was 1.51 m including capillary fringe 0.14 m and available depth for 10% porosity 1.35 m. The soils in this area were feasible for landscape vegetation. The soil in area C was feasible for bottom fill purpose only due to low water holding capacity.

• 한국음향학회지
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• 제42권1호
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• pp.16-24
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• 2023

해수의 염분은 수중 음속 산출에 있어 영향을 적게 미치는 변수로 알려져 있다. 본 연구는 여름철 양쯔강(장강) 희석수가 동중국해로 확장하는 과정에서 양쯔강 하구 인근 해수의 저염분이 음속의 수직구조에 어떻게 영향을 미치는지를 파악하였다. 음속 산출에 활용된 염분을 관측치와 고정값으로 구분 후 각각의 음속을 비교한 결과, 양쯔강 희석수의 영향으로 염분약층이 수온약층보다 강하게 형성되는 경우 음속이 상이하게 나타났다. 또한, 음원을 수온약층의 중간 심도에 위치하여 음선경로를 추적한 결과 염분약층이 강한 경우 고정된 염분으로 계산된 음속에서는 확인되지 않는 수중음파통로가 나타났다. 이러한 결과를 바탕으로 본 연구는 여름철 저염분수에 의한 강한 염분약층이 형성된 조건에서 음속 산출 시 Expandable Bathy Thermograph(XBT)보다는 실제 염분이 고려된 관측기기인 Expendable Conductivity Temperature Depth(XCTD)와 Expendable Sound Velocimeter(XSV)의 활용이 중요함을 제시한다.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.1-10
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• 2021

본 연구에서는 해상(수상) 교량기초 시공 시 석션압으로 간편하게 설치될 수 있는 원형관 공법을 개발하고자, 실내 모형실험을 통하여 저수심 모래지반에 원형관 관입 시 설치 석션압을 평가하였다. 포화된 사질토의 반복실험을 위해 3개의 진동발생기를 활용한 진동다짐 토조 시스템을 구축하였고, 지반강도 확인을 위하여 소형 콘관입 장비를 활용하였다. 진동다짐 토조 시스템은 내부의 모래지반에 반복적으로 진동을 가하여 효율적으로 균질한 모래지반을 확보할 수 있었다. 다양한 지름과 두께를 가지는 원형관 모형체를 제작하고, 다양한 수심조건에 대하여 석션관입 실험을 수행하였다. 실험을 통한 석션압 분석결과 원형관의 관입깊이가 커짐에 따라 석션압은 커지고 지름이 클수록 원형관을 관입시키는데 필요한 석션압은 작아지는 것을 확인하였다. 특히, 수위가 낮을수록 석션관입을 위해 원형관 내부에서 끌어 올려야 하는 수두가 커지는 반면, 높아진 수두에 의한 물의 무게는 원형관의 전체 자중을 증가시켜 관입에 필요한 석션압은 작아짐을 알 수 있었다. 따라서, 저수심 조건에서 석션압을 이용하여 원형관을 설치할 경우 수심의 영향을 고려하여 설계 석션압을 결정해야 할 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.573-576
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• 2006

The objective of the study is to investigate the depth of penetration of concrete water forced in under pressure. For this purpose, the experiments for the depth of penetration by selecting the factors and levels such as water pressure, pressure time were executed. The flow of water of concrete examined theoretically and experimentally. As a result, It is found that in the case of low water pressure approximately 0.15Mpa or less, the flow is Darcy seepage flow, the same as flow in an ordinary sand stratum, whereas in the case of high water pressure, the flow is diffused seepage flow accompanied by internal deformation of concrete.

• 한국수산과학회지
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• 제50권2호
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• pp.207-218
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• 2017

Seawater with salinity of 32.5 psu or less is observed in the southern Japan/East Sea (JES) every autumn. It is confined to a surface layer 30-45 m in depth that expands to cover the entire JES in October. Two sources of "autumn low-salinity water" have been identified from historical hydrographic data in the western JES: East China Sea (ECS) water mixed with fresh water discharge from the Yangtze River (Changjiang) and seawater diluted with melted sea ice in the northern JES. Low-salinity water inflow from the ECS begins in June and reaches its peak in September. Low-salinity water from the northern JES expands southward along the coast, and its horizontal distribution varies among years. A rare observational study of the entire JES in October 1969 indicated that water with salinity less than 33.0 psu covered the southwestern JES; the lowest salinity water was found near the Ulleung Basin. In October 1995, the vertical distribution of salinity observed in a meridional section revealed that water with salinity of 33.6 psu or less was present in the area north of the subpolar front.