• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.143-150
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• 2011

Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban area. Therefore, it is important to analyze the head losses at manholes, especially in case of surcharged flow. The stream characteristics were analyzed and head loss coefficients were estimated by using the computational fluid dynamics(CFD) model, FLUENT 6.3, at surcharged square manhole in this study. The CFD model was carefully assessed by comparing simulated results with the experimental ones. The study results indicate that there was good agreement between simulation model and experiment. The CFD model was proved to be capable of estimating the head loss coefficients at surcharged manholes. The head loss coefficients with variation of the ratio of manhole width(B) to inflow pipe diameter(d) and variation of the drop height at surcharged square manhole with a straight-path through were calculated using FLUENT 6.3. As the ratio of B/d increases, head loss coefficient increases. The depth and head loss coefficient at manhole were gradually increased when the drop height was more than 5cm. Therefore, the CFD model(Fluent 6.3) might be used as a tool to simulate the water depth, energy losses, and velocity distribution at surcharged square manhole.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.731-736
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• 2011

A pneumatic driving solenoid valve operates pneumatic control devices by opening/closing operating flow passage when the command is given by control system for the liquid-propellant feeding system of space launch vehicle. The simulation model of pneumatic driving solenoid valve is designed with AMESim to verify the designs and evaluate the dynamic characteristics and pneumatic behaviors of valve. To validate a valve simulation model, the simulation results of their operating durations of valve by AMESim analysis are compared with the results of experiments. In addition, the results of internal flow simulation with FLUENT are utilized to improve the accuracy of valve-modeling. Using the model, we analyze performance of valve; opening/closing pressure, operating time on various design factors; shape of control valve seat, drainage seat, rate of sealing diameter, volume of control cavity. This study will serve as one of reference guides to enhance the developmental efficiency of ventilation-relief valves with the various operating conditions, which shall be used in Korea Space Launch Vehicle-II.

• Fibers and Polymers
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• v.7 no.3
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• pp.317-322
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• 2006

Reduction of yam hairiness by nozzles in ring spinning and winding is a new approach. Simulation of the airflow pattern inside the nozzles provides useful information about actual mechanism of hairiness reduction. The swirling air current inside the nozzles is capable of wrapping the protruding hairs around the yam body, thereby reducing yam hairiness. Since production rate of winding is very high and the process itself increases yarn hairiness any method to reduce the hairiness of yarns at this stage is a novel approach. A CFD (computational fluid dynamics) model has been developed to simulate the airflow pattern inside the nozzles using Fluent 6.1 software. In this study, both S- and Z-type nozzles having an axial angle of 500 and diameter of 2.2 mm were used for simulation studies. To create a swirling effect, four air holes of 0.4 mm diameter are made tangential to the inner walls of the nozzles. S- and Z-twisted yams of 30 tex were spun with and without nozzles and were tested for hairiness, tensile and evenness properties. The total number of hairs equal to or exceeding 3 mm (i.e. the S3 values) for yam spun with nozzle is nearly 49-51 % less than that of ring yams in case of nozzle-ring spinning, and 15 % less in case of nozzle-winding, while both the yarn types show little difference in evenness and tensile properties. Upward airflow gives best results in terms of hairiness reduction for nozzle-ring and nozzle wound yams compared to ring yarns. Yarn passing through the centre of the nozzle shows maximum reduction in S3 values.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.328-333
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• 2012

In this study, CFD simulation was performed with commercial CFD code FLUENT for the 3D mixing tank model (1 m in a diameter and 2.5 m in a height) of DME-Propane liquified fuels. Initial condition set-up with existence of DME 146 l at the upper side of mixing tank and Propane 770 l at the lower side of mixing tank. Characteristics of mixture and fluid flow were observed for 34 hours simulation. Two liquid fuel were uniformly mixed within range of 3 mol% after 24 hours, and range of 1 mol% after 34 hours. The simulation result following 4 hours was verified with KOGAS experimental data.

• Journal of Korean Association for Spatial Structures
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• v.21 no.1
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• pp.51-59
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• 2021

In this paper, the effect of the turbulence intensity in across-wind direction on the wind load in CFD(Computational fluid dynamics) simulation was analyzed. 'Ansys fluent' software was used for CFD simulation. And the fluctuating wind speed applied to the simulation was generated according to Korean Design Standard and Von Karman wind turbulence model. The turbulence intensity in across-wind direction for simulation was applied from 0 to 100% of the turbulence intensity in along-wind direction. The analysis results showed that the turbulence intensity in across-wind direction had a particularly great effect on the wind load in across-wind direction.

• Journal of the Korean Institute of Gas
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• v.4 no.1 s.9
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• pp.40-48
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• 2000

A fuel cell is an electrochemical device continuously converting the chemical energy in a fuel and an oxidant to electrical energy by going through an essentially invariant electrode-electrolyte system. Phosphoric acid fuel cell employs concentrated phosphoric acid as an electrolyte. The cell stack in the fuel cell, which is the most important part of the fuel cell system, is made up of anode where oxidation of the fuel occurs cathode where reduction of the oxidant occurs; and electrolyte, to separate the anode and cathode and to conduct the ions between them. Fuel cell performance is associated with many parameters such as operating and design parameters associated with the system configuration. In order to understand the design concepts of the phosphoric fuel cell and predict it's performance, we have here introduced the simulation of the fuel-cell stack which is core component and modeled in a 3-dimensional grid space. The concentration of reactants and products, and the temperature distributions according to the flow rates of an oxidant are computed by the help of a computational fluid dynamic code, i.e., FLUENT.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.546-550
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• 2008

In this study, 3-dimensional Computational Fluid Dynamics (CFD) analysis was induced to simulate air flow and particle motion in the axial flow cyclone separator. The commercialized CFD code FLUENT was used to visualize pressure drop and particle collection efficiency inside the cyclone. We simulated 4 cyclone models with different shape of vane, such as turning angle or shape of cross section. For the air flow simulation, we calculated the flow field using standard ${\kappa}-{\varepsilon}$ turbulence viscous model. Each model was simulated with different inlet or outlet boundary conditions. Our major concern for the flow filed simulation was pressure drop across the cyclone. For the particle trajectory simulation, we adopted Euler-Lagrangian approach to track particle motion from inlet to outlet of the cyclone. Particle collection efficiencies of various conditions are calculated by number based collection efficiency. The result showed that the rotation angle of the vane plays major roll to the pressure drop. But the smaller rotation angle of vane causes particle collection efficiency difference with different inlet position.

• Fire Science and Engineering
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• v.29 no.5
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• pp.42-50
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• 2015

Three simulation approaches for turbulence were applied for the computation of propane dispersion in a simplified real-scale urban area with one building:, Large Eddy Simulation (LES), Detached Eddy Simulation (DES), and Unsteady Reynolds Averaged Navier-Stokes (RANS). The computations were performed using FLUENT 14, and the grid system was made with ICEM-CFD. The propane distribution depended on the prediction performance of the three simulation approaches for the eddy structure around the building. LES and DES showed relatively similar results for the eddy structure and propane distribution, while the RANS prediction of the propane distribution was unrealistic. RANS was found to be inappropriate for computation of the gas dispersion process due to poor prediction performance for the unsteady turbulence. Considering the computational results and cost, DES is believed to be the optimal choice for computation of the gas dispersion in a real-scale space.

• Journal of Navigation and Port Research
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• v.42 no.4
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• pp.283-290
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• 2018

Due to the environmental factors of the sea, ship accidents always contain an inclination angle. The change in the ship affects not only the evacuation speed of passengers but also the fire growth in the ship. For this reason, when analyzing the fire, it is necessary to analyze the risks by considering conditions of inclination. In this study, the temperature that affects the fire was calculated by alteration of ship's heel and trim angle and analyzed using FLUENT. Based on fire occurrence position, evacuation should be done within 37 seconds under the condition of $-10^{\circ}$ heeling angle and 36 seconds under the condition of $-10^{\circ}$ trim angle. However, it was predicted that the evacuation will not be affected under the conditions of $+10^{\circ}$ heel angle and $+10^{\circ}$ trim angle. For these reasons, it is confirmed that when the ship is on fire, evacuation measures should be considered based on the heel and trim conditions as per the location of the fire.

• Journal of Korea Water Resources Association
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• v.30 no.5
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• pp.467-475
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• 1997

In this study, breakwater model which has several outlet pipes to discharge heated water is settled in the experimental open channel and velocity distribution of wall jet is measured. Numerical simulation of velocity structure of wall jet using 3-dimensional computer model. Fluent model, is also carried out. The calculated results are verified with the experimental results and the flow characteristics of wall jet are investigated. The length of zone of flow establishment of wall jet is shorter than that of free jet, and the diminution rate of jet centerline longitudinal velocity is larger than that of free jet. Characteristics of buoyant jet and non-buoyant simple jet simulated by Fluent model are compared. Near the outlet pipe, in the region where x/lQ is over 15, this is reversed. Comparison of vertical distribution of longitudinal velocity shows that positive velocity of non-buoyant jet is bigger than that of buoyant jet in the bottom layer and in the upper layer, negative velocity of non-buoyant jet is bigger too. Flow separation in free surface of the buoyant jet occurs in smaller distances from the outlet than the non-buoyant jet. Buoyant jet expands faster than the non-buoyant jet in vertical direction.