• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.4
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• pp.53-59
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• 2008

If fire is occurred in the subway, the train must be moved to the closest station and make passengers get off the train. As a matter of fact, the Fire of Dae-gu Subway was coped with this way. But, the fire smoke extraction system of real subway stations have not designed to deal with fire of trains yet. Therefore, we have to establish a plan of station railroad for preventing from unexpected damage when the fired train comes to the station. The purpose of this study is to establish the effective smoke extraction measure that is to prevent stations from damage by the scale-down experiment.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.1
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• pp.8-15
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• 2014

In this study, flow characteristics around the hull form of KLNG are investigated by numerical simulations. The numerical simulations of the turbulent flows with the free surface around KLNG have been carried out at Froude number 0.1964 using the FLUENT 6.3 solver with Reynolds stress turbulence model. Several GEOSIM models are adopted to consider the scale effect attendant on Reynolds number. Furthermore, a full scale ship is calculated and the result is compared with the numerical results of GEOSIM models. The calculated results of GEOSIM models and the full scale ship are compared with the experiment data of MOERI towing tank test and Inha university towing tank test. Moreover, wake distribution on the propeller plane of the full scale ship is estimated using the numerical results of GEOSIM models. The prediction result is directly compared with the simulation result in full scale.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.9-15
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• 2009

In this study, the l/35 reduced-scale model experiment were conducted to investigate designed ventilation system performance at rescue station in tunnel fire. A model tunnel with 2 mm thick of steel, 10 m long, 0.19 m high and 0.26m was made by using Froude number scaling law. The cross-passages installing escape door at the center. were connected between accident tunnel and rescue tunnel. The n-heptane pool fire, $4cm\times4cm$, with heat release rate 698.97W were used as fire source. The fire source was located in the center and portal of accident tunnel as Worst case.. An operating ventilation system extracted smoke amount of 0.015 cms. The smoke temperature and carbon monoxide. concentration in cross-passage were measured to verify designed ventilation system. The results showed that, in center fire case without ventilation in accident tunnel, smoke did not propagated to rescue station. In portal tire case, smoke spreaded to rescue station without ventilation. But smoke did not propagated to rescue station with designed ventilation.

• Tunnel and Underground Space
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• v.16 no.6 s.65
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• pp.526-535
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• 2006

An experimental study was carried out on a reduced scale tunnel model to grasp the behavioral feature of fire-induced smoke in the long tunnels. Based on Froude modeling, the 1/50 scaled tunnel model (20 m long) was constructed by acrylic tubes and paraffin gas was released inside the tunnel to simulate the 20 MW fire-induced smoke. me test results show, that after approximately 2 minutes of fire generation, was descended from the tunnel ceiling through the decrease of buoyancy, then it was symmetrically propagated about 90 meters for 4 minutes before jet fans were operated. The smoke was effectively controlled when the jet fans were operated and an air stream velocity was getting closed to reach a critical velocity (the minimum air velocity that requires to suppress the smoke spreading against the longitudinal ventilation flow during the tunnel fire situations). It was also found out that a range of smoke was spreaded about 3 meters from the origin of fire but the range was not propagated to the escape direction anymore. The early stage of the In operation, however, showed that the smoke was hardly controlled. It means that the operation of emergency ventilation system has many dangerous factors such as an intercepting breathing zone.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.4
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• pp.335-344
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• 2006

The domestic standards which used the standards of Road Association of Japan standards presents the distances of between jet-fans by the caliber of jet-fan. However, the Permanent International Association of Road Congress (PIARC) encourages it to be ten times a diameter of the tunnel. The distance of jet-fans installed in bases of two standards differs as much as two times, as so the proper basis after analysis of internal air current is needed since such difference can lead to disadvantage for selection of ventilation configuration. Based on Froude modeling theory, 1/40 scale acrylic model of a tunnel (215mm in diameter and 6.9m in length) and jet-fan (26.3mm and 31.6mm in caliber) was made for the measurement of changes in pressure and velocity due to the extension of tunnel for analysis of internal air current. And we measured the changes in pressure of surroundings of a jet-fan for confirmation of recirculation due to the exterior airs when the jet-fan is on. The results of the model test show that internal air current was not influenced by the caliber of jet-fan and its changes in pressure and velocity were stable in the point where it was nine times of diameter of the tunnel. Also the recirculation when the jet-fan is on could be verified. According to such results, in the cases of installing jet-fan in tunnels, the distances between jet-fans needs to be more than nine times the diameter.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.620-631
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• 2022

This paper shows the numerical prediction of the change in oil outflow rate according to the orifice shape of a damaged ship by using the computational fluid dynamics (CFD) analysis method. It also provides discharge coefficients for various orifice shapes to be used in theoretical prediction approaches. The oil outflow from the model ship was analyzed using a multiphase flow method under the condition that the Froude and Reynolds number similitudes were satisfied. The present numerical results were verified by comparing them with the available experimental data. Along with the aspect ratio of the orifice and the wall thickness of the cargo tank, the effects of the orifice shapes defined by mathematical figures on the oil outflow were investigated. To consider more realistic situations, the investigation of the ef ect of the crushed iron plate around the damaged part was also included. The numerical results confirmed the change in oil outflow time for various shapes of the damaged part of the oil tank, and discharge coefficients that quantify the viscous effects of those orifice shapes were extracted. To verify the predicted discharge coefficients, they were applied to an oil spill estimation equation. As a result, a good agreement between the CFD and theoretical results was obtained.

• Bulletin of the Society of Naval Architects of Korea
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• v.25 no.4
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• pp.7-12
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• 1988

The Resistance Committee of Korea Towing Tank Conference extended the Cooperative Experimental Study Program(1985)[1] to perform the geosim tests by exchanging the five different scaled Series 60, $C_B=0.60$ models between the participating organizations and 13 sets of resistance data have been obtained. The test results are compared among the participating towing tanks and also with the results given in the report of the Resistance and Flow Com-identify the mittee of 18th ITTC. The form factor of each model is derived by Prohaska's method to investigate its dependency on $R_n$. On the other hand, at each $F_n$, form factors are also derived by Telfer's method to relation between $F_n$ and form factor. For this hull form, form factors show relatively weak dependency on $R_n$ and strong dependency on $F_n$. And it is also found that dependencies on both have a cross relation. It seems that further study should be continued to understand more clearly the physical phenomena involved in this problem.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.150-150
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• 2020

본 연구에서는 수리모형실험을 통하여 원형 다단 실린더 게이트 형식의 취수시설에서 발생하는 공기연행을 분석하였다. 수리모형실험의 원형은 경상북도 청도군에 위치한 운문댐의 "운문댐 안전성 강화사업"에서 계획되고 있는 신설취수탑을 기준으로 상사법칙은 Froude상사법칙을 적용하고 1/20의 모형 축척을 가지는 취수탑의 국부모형에 하류단 수위를 고려하기 위해 유량조절시설을 설치하여 실험을 실시하였다. 실험조건은 크게 두 가지로 구분하였으며, 수면으로부터 유입구 상단부까지의 거리 ∆h1(m)과 유입부 저수지 저류 수위와 하류단 유량조절시설간의 수위차인 ∆h2(m)이며, ∆h1에 대한 조건은 0.01m~0.06m로 0.01m 간격으로 6가지, ∆h2에 대한 조건은 0.10m~1.70m로 0.20m간격으로 9가지로 이를 조합하여 총 54개 CASE에 대해 진행하였다. 실험결과 공기연행 발생 시 그에 따른 영향을 평가하기 위해 발생 정도에 따라 미발생(Not Occur), 간헐적(Intermittent), 빈번한(Frequent), 지속적(Continuation), 공기 폭발(Air Explosion)로 분류하였으며, 각 공기연행 발생 시 취수유량의 감소율 및 영향을 분석한 결과 간헐적 공기연행 발생 시 최대 약 3.75%의 취수유량 감소, 빈번한 공기연행 발생 시 취수유량은 전체적으로 10%, 최대 약 13.19% 감소하였으며, 지속적 공기연행 발생 시 발생 이후 ∆h2증가에 의한 취수유량의 증가가 거의 이루어지지 않으며, 최대 56.25%의 취수유량이 감소, 공기 폭발 발생 시 취수유량의 영향은 지속적 발생과 비슷하나 관내 공기 포집 후 유입구로 방출 시 관에 강한 충격을 주어 안정성에도 큰 영향을 미칠 것으로 판단되어, 이에 안정성 및 취수유량 감소율을 고려하여 빈번, 지속, 공기 폭발 발생 영역에서의 취수는 적합하지 않으며, 공기연행 미발생 및 간헐적 발생 영역에서의 취수 시 목표 취수유량이 1.00~4.00(㎥/s)일 때 ∆h1= 0.40m 이상, 4.00~9.30(㎥/s) 일 때 ∆h1= 0.60m 이상, 9.30~9.53(㎥/s) 일 때 ∆h1=0.80m 이상, 9.53~9.65(㎥/s) 일 때 ∆h1= 1.00m 이상에서 취수유량 감소율 3.75% 이내로 취수유량의 확보가 가능하다. 이러한 결과는 원형 다단 실린더 게이트 형식의 취수시설에 대해 취수 시 수면와류에 의한 Air Core와 그에 따른 공기연행의 발생 조건과 영향을 수리모형실험을 통해 확인함으로써 실제 운용 시 보다 안정적이고 효율적인 운용에 대한 자료로 활용될 수 있을 것으로 판단되며, 추가로 수치해석을 통한 비교 및 공기연행과 관내 공기포집 정도에 대한 연구를 통해 보다 정확한 자료제시가 가능할 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1822-1826
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• 2009

최근 국내 하천복원사업의 방향(패러다임)이 구하도를 포함한 홍수터의 중요성을 인식하게 됨에따라 과거 하천사업 시 발생되었던 폐천구역을 가능한 한 하천구역에 편입하여 보존하려는 노력이 시도되고 있다. 본 연구는 하천복원사업의 일환으로 함평천 구하도 복원을 함으로써 발생할 수 있는 흐름특성변화 및 하상변화를 파악하기 위한 목적으로 수리모형실험과 수치모의를 수행하였다. 실험대상구간은 함평천 중류 구하도 복원구간(1.34 km)이며, 수리모형은 Froude 상사법칙에 따라 수평축척 1/50, 연직축척 1/25의 모형으로 제작하였다. 실험조건으로는 재현기간 50년, 100년의 홍수량과 강턱유량 두 케이스$(100\;m^3/s$, $120\;m^3/s)$를 적용하였고, 구하도 복원수로의 흐름특성은 고정상 조건에 대해 분석하였다. 구하도 복원전/후의 홍수위 비교를 통해 구하도 복원후의 하도에서는 단면확대로 인한 통수능 증가로 홍수위 저감효과를 확인 할 수 있었다. 구하도 복원후의 유속변화는 통수능의 증가로 복원전에 비해 저감되었다. 기존하도와 복원하도간의 유속차가 다소 크게 나타났는데 이는 복원하도의 단면형상과 와류발생으로 인해 나타난 것으로 판단된다. 복원하도내의 유황은 일부구간에서 흐름정체현상과 역류현상이 발생되는데 이 구간에는 퇴적현상이 예측된다. 수리모형실험의 유사퇴적경향과 FESWMS 모형의 하상전단력을 비교한 결과는 유사하게 나타났으며, 복원하도의 넓은 둔치지역에 넓은 퇴적층이 형성되어 차후 환경구조물 등을 이용한 흐름제어 및 유지관리대책에 의한 문제해결이필요할 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.4
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• pp.123-129
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• 1993

Because the existing scour prediction formulas for plunge pools of pipe culverts and spillways give a wide range of predicted scour depths, it is difficult to estimate actual scour depths. A review of literature showed that wide range of predicted values was caused mostly by lack of thorough analysis of the scour mechanism. In this study, the effects of the parameters govering scour were examined, and the scour potentials were measured. The major variables govering scour were the velocity and size of jet impinging into the plunge pool, the submerged weight of bed material, the ratio of jet size to bed material size, the tail watr depth of the plunge pool, and the angle of jet impact on water surface. The ratio of jet size to bed material size to bed material size was found to be another significant parameter affecting scour for larger bed materials. A densimetric Froude nember of the bed material in incipient motion was formulated. This number represented the scour potential of the jet at the point where the bed material was tested.