• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.5
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• pp.386-393
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• 2007

This paper studies the ventilation characteristics according to the jet fan location at the long road tunnel using the CFD software 'FLUENT' which is based on the finite volume method. The tunnel model used in the analysis has a length of 1600m, a cross sectional area of $120m^3$, and is composed of 3 lanes and one way. The velocity profile, the distribution of CO concentration and the ventilation flow rate within the tunnel are analyzed, respectively. In the analysis, it is found that the dependence of the ventilation flow rate upon the jet fan location is small, but the CO concentration in the tunnel is at the lowest when the jet fans are installed near the tunnel outlet. An air stream right below the jet fan is almost inactive due to the strong stream injection near the jet fan. Thus, the pollution level below the jet fan must be higher than the other area.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.275-280
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• 2002

Results of a numerical simulation of a flowing of the underwater vehicles hull with the pump-jet nozzle are presented. It was calculate velocity distributions and coefficients of the lift force and the longitudinal moment of the hull with the pump-jet nozzle and isolated hull for some values of angle of attack. It was shown that the area of tile influence of the nozzle on the velocities distribution of the hull and character of changing of coefficients of the lift force and the longitudinal moment and their derivatives depending on angle of attack.

• Journal of ILASS-Korea
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• v.11 no.2
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• pp.105-112
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• 2006

A unique feature of fluidic atomizers is that the nozzle geometry produces a thin capillary Jet which is forced to oscillate on a 2-dimensional plane through the use of a passive feedback mechanism. The objective of the current work is to characterize the influence of the stagnation pressure at the nozzle exit, jet oscillation and stretching on the breakup properties of the capillary ligament. To achieve this, shadow graph technique is used to measure size, shape, velocity and the number density of the droplets as a function of the position within the spray fan. The breakup length, defined as the radial distance from the breakup point, is analyzed as a function of the non-dimensional parameters. Finally, a kinematic model is developed to simulate the breakup of the oscillating jets at low stagnation pressures. Using the existing jet breakup theories, the model is used to predict the size and diameter distribution of the droplets after primary atomization.

• Wind and Structures
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• v.27 no.2
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• pp.89-100
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• 2018

3D simulations based on an impinging jet were carried out to investigate the flow field of a steady downburst and its effects on a high-rise building by applying the SST k-${\omega}$ turbulence model. The vertical profile of radial wind speed obtained from the simulation was compared with experimental data and empirical models in order to validate the accuracy of the present numerical method. Then wind profiles and the influence of jet velocity and jet height were investigated. Focusing on a high-rise building, the flow structures around the building, pressure distributions on the building surfaces and aerodynamic forces were analyzed in order to enhance the understanding of wind load characteristics on a high-rise building immersed in a downburst.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.309-311
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• 2015

The MILD(Moderate or Intense Low-oxygen Dilution) combustion has been considered as one of the promising combustion technology for high thermal efficiency and low emissions. In this paper, the effect of fuel oxygen impingement on formation of MILD combustion was analyzed using numerical simulation. This investigation was simulated under the thermal intensity $0.04MW/m^3$ and equivalence ratio 0.91. The results show that the temperature distribution was become relatively uniform and the amount of CO emission was decreased as the increase of oxygen jet velocity and impinging angle.

• Journal of ILASS-Korea
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• v.28 no.2
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• pp.68-74
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• 2023

In this study, the thickness of the liquid sheet formed by a low speed impinging jet onto a wall was measured by the direct contact method. The spatial distribution characteristics of the sheet thickness in the radial and circumferential directions, and the effects of jet velocity and liquid viscosity were analyzed. The measurement results were compared with the theoretical predictions for two impinging jets. The wavy surface was observed for low viscosity water, but not for high viscosity glycerol solutions. The sheet thickness decreased as the circumferential angle or the distance from the impinging point increased. The sheet thickness increased as the liquid viscosity increased. Comparison with the theoretical predictions showed some differences from the measurement results.

• Journal of ILASS-Korea
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• v.29 no.2
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• pp.75-82
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• 2024

In this study, the thickness of the liquid sheet formed by a splash plate nozzle at low jet velocities was measured by the direct contact method. The spatial distribution characteristics of the sheet thickness in the radial and circumferential directions, and the effects of jet velocity and liquid viscosity were analyzed. The wavy surface was observed for low viscosity water, but not for high viscosity glycerol solutions. The sheet thickness decreased as the circumferential angle or the distance from the impinging point increased. The sheet thickness increased as the liquid viscosity increased. Comparison with the theoretical predictions for two impinging jets showed some differences from the measurement results.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.192-198
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• 2004

A numerical study was conducted to determine the effects of high temperature air, including equivalent ratio on flow field, temperature, evaporation, and overall temperature distribution in gas turbine combustor. A sector model of a typical wall jet can combustor, featuring introduction of primary air and dilution air via wall jet, was used in calculations. Flow field and temperature distribution were analyzed. Operating conditions such as inlet temperature and overall equivalent ratio were varied from 373 to 1300 K, and from 0.3 to 0.6, respectively, while any other operating conditions were fixed. The RNG ${\kappa}-{\varepsilon}$ model and eddy breakup model were used for turbulence and combustion model respectively. It was found that the increase with the inlet air temperature, velocity in the combustor is accelerated and evaporation of liquid fuel is not affected in primary zone, high temperature inlet air enhances the evaporation and improves overall temperature distribution factor.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.251-262
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• 1995

The goal of this study is to provide fundamental information on the design of a new diesel injector system. The cylindrical disk spray was made by an impinging disk insited below the exit of air-assist atomizor. The disintegration processes on a twin-fluid atomization by air-assist atomizor were investigated. Liquid jet was disintegrated at the condition that wavelength was equal and longer than the circumference of the liquid jet, .lambda. .geq. .pi.do. However, the wavelength and the diameter of the liquid jet were decreased according to the increasing of air velocity. The relative density distribution of droplets and pattern of spray by impinging disk were investigated with a C-CCD. Optimum design conditions for cylindrical disk spray were also achieved. The pattern of cylindrical spray can classified according to the size of the disk and the distance from the nozzle tip to the disk. When the space of the disk and the nozzle tip was narrow and the diameter of the disk was larger than that of the air orifice of the nozzle exit, the good distribution of spray could be achieved. When the air flowrate was constant, the spray width was decreased according to the increasing of the liquid flowrate. When the liquid flowrate was constant, the spray width was decreased according to the increasing of the air flowrate.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.357-366
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• 1986

The flow characteristics of two-dimensional turbulent offset jet which is discharged parallel to a solid wall has been studied experimentally and numerically. In the experiment, 3-hole pitot tube and 2 channel constant temperature hot-wire anemometer are used to measure local mean velocity, turbulence intensity and Reynolds stress while scannivalve is used to measure the wall pressure distribution. It is confirmed experimentally that local mean velocity is closely related to wall pressure distribution. It is also verified that for large Reynolds numbers and fixed step height there exists a similarity in the distribution of wall pressure coefficient. The maximum values of turbulence intensity occur in the top and bottom mixing layers and the magnitude of Reynolds stress becomes large in the lower mixing layer than in the top mixing layer due to the effect of streamline curvature and entrainment. In the numerical analysis, standard k-.epsilon. model based on eddy viscosity model and Leschziner and Rodi model based on algebraic stress model are adopted. The numerical analyses predict shorter reattachment lengths than the experiment, and this difference is judged to be due mainly to the problem of turbulence model constants and numerical algorithm. This also causes the inconsistency between the two results for other turbulence quantities in the recirculation region and impingement region, which constitutes a subject of a continued future study.