• Journal of Industrial Technology
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• v.25 no.A
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• pp.191-201
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• 2005

A numerical analysis was done for a tunnel fire in a 1000m road tunnel. A cartesian coordinate was adopted to make a computational grid sytem which has 448,000 computational cells. A transient flow phenomena in the tunnel was simulated by the commercial code of PHEONICS from the ignition of fire to 600 seconds by the interval of 100 seconds. Total computational time of about 44 hours was required to get a convered solution in each time step. The purpose of this research is to analyze of the backlayering pheonomena and recirculation flow in a tunnel. The compuational results say that the backlayering does not happens near the fire of vehicle in this case because the vehicle fire is located at the outside of recirculation zone of flow ocuured near the jet fan. In this research, onset of backlayering pheonomena could be escaped if jet fan is set 95m in front of the the fire of vehicle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.346-351
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• 2017

A numerical study has been conducted to investigate flow characteristics of STED with ram structure shape. By increasing the attack angle of shock cone, vacuum pressure is increased because of oblique shock at ram structure and separation point moved to the downstream of the second throat. By increasing blockage ratio, expansion wave angle is increased at ram structure while vacuum pressure is constant.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.2
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• pp.18-24
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• 1999

Liquid ramjet combustor is closely connected with complex phenomena due to a series of processes such as intake air, spray, mixing, and combustion. The present numerical experiments were peformed to investigate these flow characteristics for two and three dimensional liquid ramjet combustor. Grid system was made with three domains: intake region where air is supplied and fuel is injected, combustor and nozzle region, and exit atmosphere region. The numerical results showed that two and three dimensional flow patterns in recirculation region of combustor were significantly different each other and spray model was necessary to predict correctly the chemical reaction flow characteristics. Numerically examined for two different location of fuel injector, one is located on the bottom position of curved intake and the other is located on the top position. We found that bottom position of fuel injector is better than top position because fuel influx to the recirculation region which is need to sustain chemical reaction is more than the latter.

• Fire Science and Engineering
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• v.19 no.2 s.58
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• pp.37-44
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• 2005

We have conducted a numerical simulation under three-dimensional unsteady conditions in order to analyze the characteristics of flow and the distribution of $CO_2$ agent concentration according to the number of $CO_2$ agent nozzle. The engine room of a ship was selected as a protection space, and flow fields and $CO_2$ concentration fields were measured. In case of increasing the number of $CO_2$ nozzle from 2 nozzles to 4 nozzles, the distribution of CO2 concentration showed low, and in case of increasing the number of $CO_2$ nozzle to above 6 nozzles, the recirculating flow affected to all region was generated. In case of increasing the number of $CO_2$ agent nozzle to above 4 nozzles, the iso-concentration line below 0.36 expanded or contracted slightly. Therefor, the proper number and the arrangement of $CO_2$ agent nozzle are considered when $CO_2$ fire fighting system is designed.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.1
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• pp.36-44
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• 2012

Multi-injector rocket engine using high-concentrated hydrogen peroxide and kerosene was designed and manufactured. Design requirements of a rocket engine were determined and main geometrical parameters of rocket engine were determined on the basis of fundament. Six coaxial swirl injectors were mounted on the multi-injector engine. Flow analysis in the hydrogen peroxide manifold was performed to minimize stagnation and recirculation zones. Finally, the optimized hydrogen peroxide manifold was manufactured and cold flow test was carried out to confirm mass flow rate per uni-element, spray pattern and atomization characteristics. The results of cold flow test showed that the mixing head design process was successful and enough to use as a essential database for the development of a full-scale engine.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.365-371
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• 2014

A numerical simulation was conducted for the combustion chamber of a 4-step grate-firing boiler for wood pellet fuel. The flame is extended to the exit of combustion chamber, which is reproduced by present numerical method based on a homogeneous reaction model. Flow field from the simulation shows a strong recirculation flow at the upstream corner of the chamber, along which the flame is extended to the exit. These combustion and flow characteristics remain unchanged for partial load operations, which suggest modification of the combustion chamber structure rather than resizing should be effective to improve combustion characteristics. Possible modifications for combustion chamber are suggested such as relocating its exit, increasing the number of grate steps or installing internals such as guide baffles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.10
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• pp.893-899
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• 2010

A previous study showed that hemodynamics is correlated with stenosis in the coronary artery. The flow characteristics and the distributions of the hemodynamic wall parameters in the coronary artery are investigated under physiological flow condition. The present study also aims to establish the mechanism of the generation of atherosclerosis by analyzing the hemodynamic variables in the coronary artery where atherosclerosis frequently occurs. The stenosis phenomena due to atherosclerosis are related to not only the biochemical reaction between blood and blood vessels but also the hemodynamic factors sush as flow separation and oscillatory wall shear stress. As the bifurcated angle increases, the size of the recirculation area that appears in the cross section increases and disturbed flow is observed in this area. We speculate that this area is the starting point of atherosclerosis in the coronary artery.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.301-307
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• 2003

In this study, we Presented computational results on the blood flow in the sac of the Korean artificial heart. Two dimensional unsteady flow was assumed and we utilized a finite element commercial code ADINA to simulate the blood flow. Rigid body-solid contact were considered between the actuator and the blood sac and fluid-structure interaction between the blood and the sac. The three geometric models proposed in the design process were simulated to assess the hemodynamic characteristics of the models According to the computational results, a strong flow to the outlet and a stagnated flow region near the inlet were observed during systole. The sac was filled with blood and recirculating flow was generated near the outlet during diastole. Shear stress during systole had its extreme values near the outlet edge whereas the magnitude of shear stress values were relative)v high near the inlet edge and the contacting surface with the actuator.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.136-142
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• 2016

As the rapid industrialization and modernization progress of the world it is becoming a fast-paced environment pollution. And, dust or environment pollution to solve reckless diggings of natural aggregate cause a serious problem. This study was used a Blast Furnace Slag and Combined Heat and Power Plant of Fly Ash as a cement substitute to reduce $CO_2$ emissions during cement production, this study intend to suggest it's result as basic data 'Properties of Artificial Stone interior or exterior materials type utilizing industrial by-product and waste resource' utilizing Waste Porcelain and Waste Glass. As a result, it was high strength that matrix added the Combined Heat and Power Plant of Fly Ash of addition ratio 40%. Also, pre-experiment was conduct as mixing ratio of waste glass, waste porcelain on the basis of the preceding experiment, proper mixing ratio was judged that proper of waste glass, waste porcelain was mixing ratio 60, 70 (%) of appeared surface aggregate ratio more than 45%.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.4
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• pp.333-338
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• 2008

The coastal zone is a delicate and dynamic area in which the majority of a water kinetic energy is dissipated. These processes are subsequent to the transport of the beach materials. In comparison to emerged breakwaters, submerged structures permit the passage of some wave energy and in turn allow for circulation along the shoreline zone. This research aims to examine the beach erosion prevention capability of submerged structure by laboratory model. The flow characteristics behind a submerged obstacle with bottom gap were experimentally investigated at Re = $1.2{\times}10^4$ using the two-frame PIV(CACTUS 2000) system. Streamline curvature field behind the obstacle has been obtained by using the data of time-averaged mean velocity information. And the large eddy structure in the separated shear layer seems to have signification influence on the development of the separated shear layer. As bottom gap size increases, the recirculation occurring behind the obstacle moves toward downstream and its strength is weakened.