• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.1
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• pp.81-96
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• 2007

Nonlinear shoaling characteristics over surf zone are numerically investigated based on spatially averaged NavierStokes equation. We also test the validity of gradient model for turbulent stresses due to wave breaking using the data acquainted during SUPERTANK LABORATORY DATA COLLECTION PROJECT(Krauss et al., 1992). It turns out that the characteristics length scale of breaking induced current is not negligible, which firmly stands against ever popular gradient model, ${\kappa}-{\varepsilon}$ model, but favors Large Eddy Simulation with finer grid. Based on these observations, we model the residual stress of spatially averaged NavierStokes equation after Lagrangian Dynamic Smagorinsky(Meneveau et al., 1996). We numerically integrate newly proposed wave equations using SPH with Gaussian kernel function. Severely deformed water surface profile, free falling water particle, queuing splash after landing of water particle on the free surface and wave finger due to structured vortex on rear side of wave crest(Narayanaswamy and Dalrymple, 2002) are successfully duplicated in the numerical simulation of wave propagation over uniform slope beach, which so far have been regarded very difficult features to mimic in the computational fluid mechanics.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.1
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• pp.15-19
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• 2014

Recently, cyclone is used to collect fine particles in various industrial precesses, but many studies are undergoing because of cyclone's low collection efficiency. Thus, we have developed water-cyclone which minimizes disadvantages of existing conventional cyclone and designed 3 different stages depending on precessing materials. Stage 1 collects particles by using principles of conventional cyclone. Stage 2 processes acid gases by extending contact time with water film through vortex movement. Stage 3 processes uncollected substances in stage 1 and 2. Hence, we evaluate water-cyclone by experimental verification.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.118-125
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• 2009

This paper reports the size classification of nanoparticles as well as electrical tuning techniques for the cut-off diameter and collection efficiency. Classifying particles < 100 nm in diameter is quite a technical challenge using a virtual impactor with the cut-off diameter being determined geometrically. However, the proposed virtual impactor can classify particles <100 nm and tune the cut-off diameter by electrically accelerating the particles. The cut-off diameter of the proposed device was tuned from 15 to 50nm.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.210-214
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• 2007

Silicon nanoparticles are widely studied as a material with great potential for wide applications. For application to present industry, it should be easy to control the characteristics of nanoparticle including the size and structure. In this paper, we investigated the formation of Si nanoparticle using pulse plasma technology. Plasma technology is already quite common in device industry and the size of nanoparticle can be easily controlled according to plasma pulse duration. An inductively-coupled plasma chamber with RF power (13.56 MHz) was used with DC-biased grid $(-200\sim+200\;V)$ installed above the substrate. In order to measure the shape and size of nanoparticle, TEM was used. It was found that the size of nanoparticles can be controlled well with the plasma pulse duration and the collection efficiency is increased with the use of either negative or positive DC-bias.

• Journal of Korean Society for Atmospheric Environment
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• v.10 no.1
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• pp.49-56
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• 1994

Electrostatic Precipitators( EP ) are widely used in industry for controlling the emission of particulate pollutant Recently, a number of researches have been conducted to solve performance and reliability problems of EP, As a result of researches in the laboratory and of pilot scale, a technology of wide-pitch-spacing has been successfully applied to full scale units. It has been known that the wide-pitch-spacing can reduce the capital cost of newly installed precipitators, and the cost of rebuilding existing uints. In this paper, a systematic study was performed to develop a wide-pitch electrostatic precipitator. The study includes experimental and numerical work on the following : Particle collection characteristics for a bench-scale unit; gas flow characteristics( temperature and velocity distributions): other EP operating variables such as electric Power supply/control. The results are applied directly to design of wide-pitch-spacing EP and the developed numerical model was found to be a good argreement with the experimental results. The EHD simulation program is necessary to design the high efficiency EP.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.133-136
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• 2004

In-situ collection experiments were performed to analyze inflowing sedilnents behavior as a basic study of topographical change in Nakdong River Estuary. Sediment rate and bed load flux ranged from 0.0004 to $0.472\;g/cm^2/day\;and\;0.0005\~1.7579\;g/cm^2/day$, respectively. The settling velocity of suspended particulate matter was estimated in tire range of $0.339\~1.010\;cm/sec$, The grain size analysis shows that surface sediments in backside of sandbar and bed load in front of dike have a similar grain size distribution. It is considered that the source of surface sediments in backside of sandbar were flowed in from Nakdong River. In order to verify the characteristics of inflowing sediments behavior, detailed surveys around Nakdong River Estuary need to be carried out, continuously.

• Nuclear Engineering and Technology
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• v.30 no.6
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• pp.485-495
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• 1998

Migration characteristics of tracers in a rock fracture in a case of line-source and line-collection was studied. The fracture plane was discretized into a square mesh to which variable apertures were assigned. The spatially varying apertures of a fracture were generated using a geostatistical method, based on a given aperture probability density distribution and a specified spatial correlation length. The flow potential and pressure at each node were computed. Calculations showed that fluid flow occurs predominantly through a few preferred paths. Hence, the large range of apertures in the fracture gives rise to flow channeling. The solute transport was calculated using a particle tracking method. The migration plumes of tracer between injection line and withdrawal line are displayed in contour plots. The elution curves are shown to be controlled by the aperture density distribution and to be insensitive to statistical realization and spatial correlation length.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.229-233
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• 2015

In this study, we examined the removal characteristics of suspended particulate matters which are one of carcinogens to cause lung cancer. The fine dust capture by a pilot scale filtration system depends on several important variables such as humidity, initial fine dust injection volume, and flow rate. The average concentration of particulate matters in the test chamber decreased, but the ultimate collection efficiency did not change during the filtration under high humidity, compared to those of using ambient conditions The initial injection amount of fine dust did not influence the particle capturing efficiency. When the flow rate reduced from 0.6 m/s to 0.3 m/s, the dust collection time increased approximately 1.4 times. Among all variables tested, the flow rate showed the most significant effect on the removal efficiency of fine particulate matter.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.6
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• pp.675-687
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• 2012

Applying an external electric field across air filter media is one of methods to improve the filtration performance. Metal wire meshes have been commonly used as electrodes situated on both sides of a thick filter pad. For a thin filter medium a short circuit, known as the biggest drawback for applying an external electric field to air filter, can occur at the closest point between electrodes. In this study several types of insulated meshes were prepared by coating #50 meshes with a dielectric material, Nylon 66, and the filtration property of air filter was evaluated at the presence of external electric field using those insulated meshes as electrodes and compared with that of filters using bared meshes. The collection efficiency of tested filter was increased from 78% to 95% for singly charged 100 nm particles by application of external electric field. As a result, there was no significant difference in collection efficiency between filters with insulated and bared electrodes. Similar results could be also seen from the tests using polydisperse particles. Finally, through this study, we found that the insulation of mesh electrodes doesn't affect the filtration performance of fibrous air filter under external electric field.

• Journal of environmental and Sanitary engineering
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• v.10 no.2
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• pp.79-88
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• 1995

The electrostatic precipitation of Auto- Bias has the advantages of a little of power consumption by the voltage to apply only at ionizer and the prevention of fire danger by current flow over. As this ionizer wire was used WXN- Pt material of diameter 90$\mu $m, that improved ion efficiency and safety, simplified a existing source of electric power by induced Auto- Bias voltage. Also, the new type collector used electric conductivity- film wag superior a electric safety and dust collection efficiency and was possible to wash it by water. As a experiment result of this Auto- Bias electrostatic collector, the induced Auto- Bias voltage by appling D.C 4.0∼6.0kV at ionizer was 1.3∼2.3kV and then the power consumption by applied voltage was 8- l8W. The pressure loss of collector by the amount of flowing was 6.1 OmmH$_{2}$O in 300m$^{3}$/hr and showed a safe state of the dust collection. The collection efficiency by particle size was 65.1-95.8% in 0.5∼5.0$\mu $m. After corona discharge of ionizer, the remains ozone concentration was found much lower than that of ACGIH or air pollution criteria in Korea.