• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.753-760
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• 2008

The present study is concerned with aerodynamic characteristics and reference trajectory generation of Hope-X in Approach/Landing phase. To create reference trajectory generation in A/L phase, detailed informations on lift and drag coefficients of Hope-X must be provided. To obtain these informations, aerodynamic characteristics of Hope-X are analyzed using the commercial CFD code, Fluent. The A/L phase is conceptually divided into three sub-phases: the Steepglide Slope phase for stability of vehicle, the Flare Maneuver phase for safety landing, the Circular Flare for smooth connecting with these both phases. The reference trajectory is obtained by determination of flight-path angle through geometrical formulas with consideration of aerodynamic coefficient and dynamic characteristic.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.596-604
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• 2011

To improve the total efficiency of centrifugal compressor, it is necessary to reduce the disk friction loss, which is defined as the power loss. In this study, the disk friction loss due to the axial clearance and the surface roughness effect is analyzed and proposed the new empirical equation for the reduction of the disk friction loss. The rotating reference frame technique and the 2-equation k-${\omega}$ SST model using commercial CFD code FLUENT is used for the steady-state analysis of the centrifugal compressor impeller. According to CFD results, the disk friction loss of the impeller is more affected by the surface roughness than the change of the axial clearance. For the minimization of the disk friction loss on the centrifugal compressor impeller, the magnitude of the axial clearance should be designed to the same size compare with theoretical boundary layer thickness and the surface roughness should be minimized.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.50-55
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• 1996

A numerical simulation on a primary calcinator of porcelain was performed with using Fluent to calculate the heat efficiency by studying velocity vector and temperature profile according to variables such as the location of outlet and porcelain. Control-Volume based Finite Difference Method and Up-wind scheme are used for discretization of differential equation. SIMPLEC Algorithm and standard k-$\varepsilon$ turbulent model are selected to resolve the pressure-velocity coupling and the turbulent. The result of simulation showed that the whole velocity vector field in a calcinator was varied greatly according to the location of outlet. But the whole temperature profile at each zone was still high regardless of the location of outlet because of the radiation. But the temperature of a case with a outlet at sidepart of preheating or cooling zone was little high compared to the case with a outlet on the top of preheating zone. The velocity vector field and temperature profile in a calcinator were almost not affected by the location of porcelain, but the temperature inside a porcelain was much affected according to the place where it was located. The heat efficiency in a calcinator was 44.6% and the gas temperature in the outlet was about 1000 K.

• Fire Science and Engineering
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• v.23 no.4
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• pp.13-18
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• 2009

The main objective of the present study is to investigate smoke propagation in railway tunnels with rescue stations. In particular, based on measurement of HRR (heat release rate) for pool fires formed at different locations, the influence of fire source location on smoke behavior is examined. The fuel is n-heptane and pool fires are generated with a square length 4cm. With the use of MVHS (Modified Volumetric Heat Source) model for fire source, extensive numerical simulations are performed by using the commercial code FLUENT (Ver.6.3) Predicted smoke temperatures and smoke propagation are discussed. From numerical predictions, it is found that ventilation systems may be necessary in the railway tunnels because the smoke moves along the tunnel, and consequently it enters the non-accident tunnel. It is also confirmed that the cross-passage and fire protection wall systems contribute to control the smoke.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.915-922
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• 2011

In this paper, the unsteady incompressible Navier-Stokes equation coupled with energy equation was solved in order to investigate the thermal stimulation of continuous moxibustion using a commercial code (ANSYS-Fluent). In the simulations, various periods were selected for the continuous moxibustion, which was done by burning multiple disks successively. It has been found that the depth of the effective stimulation zone increases only when the replacing temperature is equal or larger than body temperature whereas the increase rate of the effective stimulation depth decreases as the number of disc increases. Further, it has been shown that the optimal period, for which the duration time of the effective stimulation zone is maximum, exists.

• Asian Journal of Atmospheric Environment
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• v.8 no.2
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• pp.81-88
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• 2014

Noise-barriers on both sides of the roadway (hereafter referred to as double noise-barriers), are a common feature along roads in Korea, and these are expected to have important effects on the near-road air pollution dispersion of vehicle emissions. This study evaluated the double noise-barrier impact on near-road air pollution dispersion, using a FLUENT computational fluid dynamics (CFD) model. The realizable k-${\varepsilon}$ model in FLUENT CFD code was used to simulate vehicle air pollutant dispersion, in around 11 cases of double noise-barriers. The simulated concentration profiles and surface concentrations under no barrier cases were compared with the experimental results. The results of the simulated flows show the following three regimes in this study: isolated roughness (H/W=0.05), wake interface (H/W=0.1), and skimming flow (H/W>0.15). The results also show that the normalized average concentrations at surface (z=1 m) between the barriers increase with increasing double noise-barrier height; however, normalized average concentrations at the top position between the barriers decrease with increasing barrier height. It was found that the double noise-barrier decreases normalized average concentrations of leeward positions, ranging from 0.8 (H/W=0.1, wake interface) to 0.1 (H/W=0.5, skimming flow) times lower than that of the no barrier case, at 10 x/h downwind position; and ranging from 1.0 (H/W=0.1) to 0.4 (H/W=0.5) times lower than that of the no barrier case, at 60 x/h downwind position.

• Fire Science and Engineering
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• v.28 no.1
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• pp.52-57
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• 2014

In this paper, the unsteady incompressible Navier-Stokes equations coupled with energy equation were solved to find out the optimal location of electrical heat trace for anti-freeze of water inside the pipe for fire protection. Since the conduction equation of pipe was coupled with the natural convection of water, the analysis of conjugate heat transfer was conducted. A commercial code (ANSYS-FLUENT) based on SIMPLE-type algorithm was used for investigating the unsteady flows and temperature distributions in water region. From the numerical experiments, the isotherms and the vector fields in water region were obtained. Furthermore, it was found that the lowest part of the pipe cross-section was an optimal position of electrical heat trace assuming the constant thermal expansion coefficient of water since the minimum temperature of the water with the position is higher than those with the other positions.

• Fire Science and Engineering
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• v.29 no.6
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• pp.33-39
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• 2015

In this paper, a numerical experiment was conducted to find out the optimal location of electrical heat trace for anti-freeze of water inside the CPVC pipe for fire protection. The unsteady incompressible Navier-Stokes equations coupled with energy equation were solved. Since the conduction equation of pipe was coupled with the natural convection of water, the analysis of conjugate heat transfer was conducted. A commercial code (ANSYS-FLUENT) based on SIMPLE-type algorithm was used for investigating the unsteady flows and temperature distributions in water region. From the present numerical experiment, it has been found that the vector field of water inside the PVC pipe is opposite to the case of steel because of the huge difference of material properties of the two pipes. Furthermore, it was found that the lowest part of the pipe was an optimal position for electrical heat trace since the minimum water temperature of the case was higher than those of the other cases.

• Fire Science and Engineering
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• v.30 no.1
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• pp.49-56
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• 2016

This paper numerically examines, straight and twisted electrical heat trace installations for their anti-freezing effects on water inside a pipe. The unsteady incompressible Navier-Stokes equations coupled with an energy equation were solved to compare the two installation methods. The heat conduction of the pipe with a heat source interacts with the natural convection of the water, and the conjugate heat transfer was considered using a commercial code (ANSYS-FLUENT) based on a SIMPLE-type algorithm. Numerical experiments, were done to investigate the isotherms and the vector fields in the water region to extract the evolutions of the minimum and maximum temperatures of the water inside the pipe. There was no substantial difference in the anti-freezing effects between the straight and twisted. Therefore, the straight installation is recommended after considering the damage and short circuit behavior of the electrical heat trace.

• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.294-299
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• 2008

The present study investigates the ventilation effects on smoke spreading with the rescue stations. Experiments for tunnel fires were carried out for n-heptane pool em at different fire locations, and the heat release rates (HRR) were obtained by addition, using the commercial code (FLUENT), the present article presents numerical results for smoke behavior in railway tunnels with rescue station, and it uses the MVHS (Modified Volumetric Heat Source) model for estimation of combustion products resulting from the fire source determined from the HRR measurement. As a result, it is found that smoke propagation is prevented successfully by the fire doors located inside the cross-passages and especially, the smoke behavior in the accident tunnel can be controlled through the ventilation system because of substantial change in smoke flow direction in the cross-passages.