• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1521-1527
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• 2009

This study is aimed to analyze the floe patterns and thermal characteristics by computer simulation under the variations of fire strength for the logitudinal tunnel, from which flow and heat distributions are predicted in the longitudinal tunnel. Through the results of numerical computations, followings are found; one is that the volume flow rate is discontinuously increasing as closer to fire location, and the other is that a critical design to get the faster flow rate is required because of existence of backlayer flow for the high fire strength in view of safety for the people in fire of the tunnel.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.6
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• pp.120-127
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• 2000

This study is concerned with evaluating the effects of acoustic excitation on the development of two stream mixing layer generated by split plate. The ratios of two velocities U1 and U2 either side of the splitter plate were such that $U_1/U_2$=1.0 (uniform flow) or $U_1/U_2$<1.0(shear flow). The mixing layers were disturbed acoustically through the edge of split plate. Quantitative data were obtained with hot-wire anemometry. Flow visualization with smoke-wire was also employed for qualitative study. the results show that the large scale structures of mixing layers are strongly affected by excitation frequency and amplitude in both uniform and shear flows. The maximum streamwise and vertical turbulent intensities of the excited flow fields are apt to be decreased as compared with those of without excitation. The flow characteristics of uniform flow are more influenced by acoustic excitation than those of shear flow.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.1
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• pp.55-62
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• 2002

A new off-surface visualization method of using the micro water droplet and laser beam sheet was presented. About a size of 5 to TEX>$10\mu\textrm{m}$ micro water droplet could be made from home-style ultrasonic humidifier, A 3 W Argon ion laser and cylindrical lens were used to generate a laser beam sheet, which interrogate specific cross section of the vortical flow field. Application of this new visualization method was conducted in KAFA small-sized low speed wind tunnel of having the test section of 0TEX>$0.9 m(W){\times}$0.9 m(H){\times}2.1 m(L)$$$. Visualization results show this method relatively easy and safe flow visualization method for wind tunnel testing. Moreover, this method is also make up for the disadvantage of smoke visualization, and can be applied to higher flow velocity range than that of smoke visualization.

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

• 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.

• 한국연소학회:학술대회논문집
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• 2001.06a
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• pp.17-22
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• 2001

The flow induced by a circular jet vertically impinging under a horizontal plate is investigated by visualization technique, using kerosene smoke in nitrogen gas to visualize the flow in the vortex as well as under the plate. The light source was the sheet beam of Ar-Ion laser. The vertical and 3-dimensional images of vortices were recorded by the digital video camera.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.6089-6097
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• 2012

This study suggested a method of detecting an incident inside tunnel by using camera that is installed within the tunnel. As for the proposed incident detection method, a static object, travel except vehicles, smoke, and contra-flow were detected by extracting the moving object through using the real-time background image differencing after receiving image from the camera, which is installed inside the tunnel. To detect the moving object within the tunnel, the positive background image was created by using the moving information of the object. The incident detection method was developed, which is strong in a change of lighting that occurs within the tunnel, and in influence of the external lighting that occurs in the entrance and exit of the tunnel. To examine the efficiency of the suggested method, the experimental images were acquired from Marae tunnel and Expo tunnel in Yeosu of Jeonnam and from Unam tunnel in Imsil of Jeonbuk. Number of images, which were used in experiment, included 20 cases for static object, 20 cases for travel except vehicles, 4 cases for smoke, and 10 cases for contra-flow. As for the detection rate, all of the static object, the travel except vehicles, and the contra-flow were detected in the experimental image. In case of smoke, 3 cases were detected. Thus, excellent performance could be confirmed. The proposed method is now under operation in Marae tunnel and Expo tunnel in Yeosu of Jeonnam and in Unam tunnel in Imsil of Jeonbuk. To examine accurate efficiency, the evaluation of performance is considered to be likely to be needed after acquiring the incident videos, which actually occur within tunnel.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.41-45
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• 2004

The dynamic particle image velocimetry (PIV) is consisted of a high frequency pulse laser, high speed cameras and a timing controller. The three velocity components of flow downstream of an axial flow fan for PC cooling system are measured using the dynamic PIV system. An Axial flow fan has seven blades of 72 mm in diameter. The rotating speed is 1800 rpm. The downstream flow is visualized by smoke particles of about $0.3-1\;{\mu}m$ in diameter. The three-dimensional instantaneous velocity fields are measured at three downstream planes. The swirl velocity component was diffused downstream and the change in time-mean vorticity distribution downstream was also discussed. The spatio-temporal change in axial velocity component with the blades passing is recognized by the instantaneous vector maps. And the dynamic behavior of vorticity moving with the rotating blades is discussed using the unsteady vorticity maps.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.4
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• pp.846-856
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• 2001

An experimental study has been made to investigate the effect on wake flow and vortex shedding frequency by vortex stabilizer in Karman vortex type air flow sensor. The conditions investigated include 3 types of shapes and 3 types of separation distances of the vortex stabilizer. The phase averaged technique and smoke-wire flow visualization method are used to understand the detail information. The rolling up position of shear layer is fixed by the influence of the vortex stabilizer. Especially, the convex type vortex stabilizer has shown the more stable repeatability and linearity regarding the vortex shedding frequency compared to the other types.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.568-576
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• 2015

In this study, scenarios based on the leakage of highly compressed air and fire occurrence turned out to be high risks in an operation stage of CAES facility were constructed and estimated. By combining Bernoulli equation with momentum equation, an expression to calculate an impact force of a jet flow of compressed air was derived. An impact force was found to be proportional to the square of diameter of fracture and the pressure of compressed air. Four types of fire scenarios were composed to evaluate an effects that seasonal change and location of fire source have on the spread behavior of smoke. Smoke from the fire ignited in the vicinity of CAES opening descended more quickly below the limit line of breathing than one from the fire occurred 10 m away from CAES opening, which is expected to occur due to a propagation of wave front of smoke. It was shown that a rate of smoke spread of the winter fire is faster than one of the summer fire and smoke from the winter fire spreads farther than one of the summer fire, which are dependent on the direction of air flow into access opening. Evacuation simulation indicated that the required safe evacuation time(RSET) of the summer and winter fires are 262, 670 s each.