• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.511-511
• /
• 2017

하천에서 홍수 예방 및 가뭄재해 방지를 목적으로 최근 4대강 살리기 사업이 수행되었다. 특히, 안정적인 용수공급 및 다양한 수재해 피해를 최소화하기위해 다기능보가 설치되었다. 설치된 보는 고정보와 가동보로 구분되며 평상시에는 고정보를 넘어가는 월류흐름이 발생하며 홍수 시에는 추가적으로 가동보를 개방하여 오리피스 흐름이 발생한다. 최근 기후변화로 인해 집중호우가 빈번히 발생하며 이는 보 주변에서 빠르고 복잡한 흐름을 유발하게 된다. 이러한 흐름특성은 보하류의 세굴문제뿐만 아니라 물받이와 바닥보호공의 안전성에 영향을 미칠 수 있다. 본 연구에서는 영상기법을 활용하여 도수가 발생하는 조건에서 고정보 하류의 물받이공 및 바닥보호공에 난류흐름특성 및 압력분포를 분석하였다. 길이 8.0 m, 폭 0.3 m를 갖는 개수로에서 실험을 수행하였으며 0.2 m 높이의 고정보는 상류경계로부터 3.0 m지점에 위치하였다. 보 하류부에서 유속성분은 비접촉식 유속측정 기법인 입자영상유속계(Particle Image velocimetry, PIV)와 기포흐름을 측정할 수 있는 기포영상유속계(Bubble Image velocimetry, BIV)를 적용하였다. 그러므로 기포 존재유무와 관계없이 보 하류부 구간에 대한 유속장 성분을 취득하였다. 도수흐름은 물받이공 및 바닥보호공 영역의 바닥면을 따라 빠른 유속을 갖는 제트류가 발생하고 수면과 바닥으로 강한 진동이 발생하여 불안정한 흐름이 야기된다. 바닥면에 작용하는 압력을 측정하기 위해 흐름방향을 따라 피에조미터를 설치하였고 압력수두 분포를 초고속카메라로 촬영하여 그 특성을 분석하였다. 실험을 결과를 통해 보 하류부에 영향을 미치는 인자를 도출하였으며 향후 보 설계기준에 반영할 수 있을 것으로 기대된다.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.16 no.1
• /
• pp.105-115
• /
• 2014

A numerical analysis on the smoke behavior and evacuee safety has been performed with computational fluid dynamics. The purpose of this study is to build computational processes for an evacuation and prevention of a fire disaster of a 3 km-length tunnel in Korea. To save computational cost, 1.5 km of the tunnel that can include a few cross-passing tunnels is considered. We are going to assess the fire safety in a road tunnel according to the smoke level, which consists of the smoke density and the height from the floor. The smoke density is obtained in detail from three-dimensional unsteady CFD analysis. To obtain proper temperature distributions on the tunnel wall, one-dimensional conduction equation is considered instead of an adiabatic wall boundary or a constant heat flux. The tunnel considered in this study equips the cross passing tunnels for evacuees every 250 m. The distance is critical in both safety and economy. The more cross passing tunnels, the more safe but the more expensive. Three different jet fan operations can be considered in this study; under- and over-critical velocities for normal traffic condition and 0-velocoty operation for the traffic congestion. The SE (smoke environment) level maps show a smoke environment and an evacuating behavior every moment.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.4 no.4
• /
• pp.12-20
• /
• 2001

The temporal variability in near-field mixing characteristics of discharging plumes in oceanic environment was investigated using the time series data of the buoyant jet parameters. Based on the currents and density profiles observed in Masan outfall site and effluent discharge flowrates for 63days of summer season, the temporal variabilities and those occurrence frequency were obtained by line plume equations. The results show that wide range of variability in Masan outfall's mixing characteristics was found due to the temporal changes of effluent flowrates and ambient oceanic conditions. The near-field dilution was in the range of 30~71 with the averaged dilution of 34, which was a good agreement with field measurements of salinity deficit. The length of mixing zone was in the range of 5.4~36.2 m with the average of 9.5 m, and the plume rise height was in the range of 8.1~10.2 m with the average of 8.9 m. However, only the 30~44% of the whole results are higher than the averages, which indicates the necessity of this frequency analysis with the continuously measured data for designing and managing the ocean outfall system.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.9 no.2
• /
• pp.98-108
• /
• 2006

The vessels, already built and is operating in Korea, have the hull form of catamaran, with LOA(Length Over All) 15 m, LBP(Length Between Perpendiculars) 12 m, GT(Gross Tonnage) 9.77ton, Light Load Displacement 15.1ton. Korean Society of Ship Inspection & Technology, Chungnam National University, Inha University, Seoul National University and Advance Marine Tech co. ltd developed by cooperation it for fishing vessels. And it used FRP(Fiber Reinforced Plastics) for hull material and main engine of diesel $360ps{\times}2800rpm{\times}2sets$ with a water jet system. Based on these results, this paper describe small leisure fishing vessels with multi-hull, in relation to the project of CTYS(Regional Reserch Center for Transportation System of Yellow Sea Inha University) that aimed to development of trimaran hull form(LOA=17m, LBP=14m(Side Hull=6m), GT=9.77ton, Light Weight=11.2 ton).

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.22 no.1
• /
• pp.25-33
• /
• 2010

The matching condition at a perforated wall with vertical slits involves the permeability parameter, which can be calculated by two different methods. One expresses the permeability parameter in terms of energy dissipation coefficient and jet length at the perforated wall, being advantageous in that all the related variables are known, but it gives wrong result in the limit of long waves. The other expresses the permeability parameter in terms of friction coefficient and inertia coefficient, giving correct result from short to long waves, but the friction coefficient should be determined on the basis of a best fit between measured and predicted values of such hydrodynamic coefficients as reflection and transmission coefficients. In the present study, an empirical formula for the friction coefficient is proposed in terms of known variables, i.e., the porosity and thickness of the perforated wall and the water depth. This enables direct estimation of the friction coefficient without invoking a best fit procedure. To obtain the empirical formula, hydraulic experiments are carried out, the results of which are used along with other researchers' results. The proposed formula is used to predict the reflection and transmission coefficients of a curtain-wall-pile breakwater, the upper part of which is a curtain wall and the lower part consisting of a perforated wall with vertical slits. The concurrence between the experimental data and calculated results is good, verifying the appropriateness of the proposed formula.