• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.256-264
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• 2004

The granular flow has been numerically studied by using DEM(Discrete Element Method). The eve교 particle is checked if it collides neighbor particles, and the next motion of the particle is predicted. The computing time has been drastically reduced by improving the collision check against neighboring particles. The comparison of the present method with ail experiment for the vibrating floor problem shows the good accuracy. The broken tower problem has been calculated to show the good comparison with the other computational result. This DEM(Discrete Element Method) can be a useful tool for constructing the constitute equation of the continuum approach of the granular flow.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.84-91
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• 2008

Generalized hydrodynamic (GH) theory for multi-species gas and the computational models are developed for the numerical simulation of hypersonic rarefied gas flow on the basis of Eu's GH theory. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. The numerical model for the diatomic GH theory is developed and tested. Moreover, with the experience of developing the dia-tomic GH computational model, the GH theory is extended to a multi-species gas including 5 species; O$_2$, N$_2$, NO, O, N. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axisymmetric flow solver. By compar-ing the computed results of diatomic and multi-species GH theories with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.84-91
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• 2008

Generalized hydrodynamic (GH) theory for multi-species gas and the computational models are developed for the numerical simulation of hypersonic rarefied gas flow on the basis of Eu's GH theory. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. The numerical model for the diatomic GH theory is developed and tested. Moreover, with the experience of developing the dia-tomic GH computational model, the GH theory is extended to a multi-species gas including 5 species; $O_2,\;N_2$, NO, O, N. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axisymmetric flow solver. By compar-ing the computed results of diatomic and multi-species GH theories with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.4
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• pp.1-6
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• 2009

Air drying technology was developed as an equipment for reducing of moisture content from wastewater treatment and waterworks sludge cake and reproducing it by reusable matter. Advantage of cyclone type pneumatic dehydrator is simple and excellent drying performance. The air drying equipment was composed to the air ejector which made high-speed fluid field, and cyclone which made circling fluid field. Dewatered cake was crushed at the high-speed zone as first step, and formed with dried powder of sphere shape by the collision between particles at the circling fluid zone. In this study, a CFD analysis has been performed to predict air-sludge particles flow in cyclone and ejector of pneumatic dehydrator. The computational results showed typical Rankine vortex structure which was frequently found in swirling flow phenomena. And the conical type wedge in lower part of a cyclone prevented accumulation of the sludge particles in the cyclone. Therefore, this technology was effective in drying of dehydrated cake of waterworks sludge.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.39-45
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• 2004

The commercial viability of heat exchanger is mainly dependent on their long-term fouling characteristics because the fouling increases the pressure loss and degrades the thermal Performance of a heat exchanger. An experimental study was performed to investigate the characteristics of fluid flow and heat transfer in a fluidized bed heat exchanger with circulating various solid particles. The Present work showed that the flow velocity range for Possible collision between the tube wall and the particles was higher with heavier density solid particles. in audition. the solid particle periodically hitting the tube wall broke the thermal boundary laver. and increased the rate of heat transfer.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.285-289
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• 2005

In recent years, RFID is widely used in industrial applications including factory, material flow, logistics and defense areas. In this paper, we developed a RFID baseband system with ASK modulation and convolutional channel code. A commercial ASK RF module is used its frequency range in $350{\sim}351$MHz and power is 10mW and the convolution code is constraint length k=3 and rate R=1/2 The performance is measured implemented the binary search algorithm as anti-collision method and we show the wave shapes whit collision occurrence.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1109-1115
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• 2023

The shell and tube-type heat exchanger was the most utilized in industrial field because of its simple structure and wide operation conditions and so on. This study was performed to investigate the characteristics of behavior of thermal flow according to operation condition of small-sized shell and tube-type heat exchanger. The operation conditions, here, were set up to flow rate of hot air with temperature of 100℃, number of baffle and cut rate of baffle(BCR) using numerical analysis. As the results, both mean relative pressure and relative pressure drop was increased with quadratic curve in case of less than BCR 25%, however, decreased linearly in case of more than BCR 25%. The collision with first baffle by flow velocity and temperature, of hot air, respectively, was depended on BCR. Further it showed that the behaviors between flow velocity and temperature were almost similar.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.1
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• pp.1-8
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• 2018

As the key equipment in deep ocean mining, the slurry pump suffers from wear and blocking problems. In this paper, high-speed photography technique is applied to track the movement rule of single particle of the coarse particle solid-liquid two-phase flow in a double blade slurry pump. The influences of particle diameter and particle density on the pass-through and collision characteristics of particles are analyzed as well. The results show that the average of the passing pump time first decreases and then increases when the particle diameter increases. The average of the passing pump time decreases by 22.7%, when the particle density increases from $1.09g/cm^3$ to $1.75g/cm^3$. Besides, the particle density has great influence on the location where the particle hits the tongue. Most particles of $1.09g/cm^3$ hit the tongue on the left side, while collision location of particles of $1.75g/cm^3$ is mainly on the top and at the right side of the tongue. The research can provide a basis for the optimization design of slurry pump in deep ocean mining system.

• Journal of Navigation and Port Research
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• v.40 no.3
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• pp.105-111
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• 2016

In ports of Korea, the marine traffic flow is congested due to a large number of vessels coming in and going out. In order to improve the safety and efficiency of these vesse's movement, South Korea is operating with a Vessel Traffic System, which is monitoring its flow 24-7. However despite these efforts of the VTS (Vessel Traffic System) officers, marine accidents are occurring continuously in their control area. VTS Officers are controlling subjectively based on their experience due to no VTS control guideline of dangerous situation among vessels. On this paper, we listened to Busan VHF channel for 3days and analyzed the message. With collision risk model, We analyzed a moment of risk which officers advise or recommend to vessel in encounter situation, VTSO's career, and day&night.

• Journal of Welding and Joining
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• v.20 no.4
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• pp.484-490
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• 2002

The formation and stability of stationary laser weld keyholes were investigated using a numerical simulation. The effect of multiple reflections in the keyhole was estimated using the ray tracing method, and the free surface profile, flow velocity and temperature distribution were calculated numerically. In the simulation, the keyhole was formed by the displacement of the melt induced by evaporation recoil pressure, while surface tension and hydrostatic pressure opposed cavity formation. A transition mode having the geometry of the conduction mode with keyhole formation occurred between the conduction and keyhole modes. At laser powers of 500W and greater, the protrusion occurred on the keyhole wall, which resulted in keyhole collapse and void formation at the bottom. Initiation of the protrusion was caused mainly by collision of upward and downward flows due to the pressure components, and Marangoni flow had minor effects on the flow patterns and keyhole stability.bility.