• 한국안전학회지
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• 제18권1호
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• pp.64-70
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• 2003

For the unconfined vapor cloud explosion(UVCE) accident by the continuous release of gas-liquid flow of various saturated liquids in a vessel at ground level, overpressures were estimated by TNT equivalency model with two estimation methods, such as UVCE I model based on a constant release time and UVCEII model based on a real travel time of vapor by dispersion and analyzed with various release conditions. As a simulation result the simple, easy, and correct method of evaluation of consequences of the UVCE accident was proposed by using consequences of UVCE I model and correlation equations for differences of overpressures between UVCE models, so that this evaluation method could be used easily in the small and medium size enterprises without using the dispersion model.

• 한국안전학회지
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• 제9권1호
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• pp.146-154
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• 1994

A series of numerical calculations are performed in order to investigate the dispersion mechanism of toxic gaseous and solid pollutants in extremely short-term and short range. The calculations are carried out in an open space characterized by turbulent boundary layer. The simulation is made by the use of numerical model, in which a control-volume based finite difference method is used together with the SIMPLEC algorithm for the resolution of the pressure-velocity coupling problem. The Reynolds stresses are solved by two-equation, k-$\varepsilon$ model modified for buoyancy. The major parameters consider-ed in this study are temperature, velocity and Injection height of toxic gases, environmental conditions such as temperature and velocity of free stream air, and topographic factor. The results are presented and discussed in detail. The flow field is commonly characterized by the formation of a strong recirculation zone due to the upward motion of the hot toxic gas and ground shear stress. The driving force of the upward motion is explained by the effect of thermal buoyancy of hot gas and the difference of inlet velocity between toxic gas and free stream.

• 한국분무공학회지
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• 제14권1호
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• pp.1-7
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• 2009

This study carried out numerical analysis of flow field of combustion gas and sorbent to test sorbent efficiency of DSI process. To provide rapid mixing for increase utilization rate of sorbent, streamwise vorticity can be introduced into the flowing streams by other means; for example, by installing vortex generators immediately downstream of the wavy trailing edge. Computing results show that the degree of sorbent dispersion depends strongly on duct structure. Highest dispersion efficiency received when vortex generator was installed inside of duct. The results presented in this study a optimum condition for the development of practical DSI process.

• International journal of advanced smart convergence
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• 제1권2호
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• pp.43-46
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• 2012

We analyzed a periodic thick mushroom structure for use as an artificial magnetic conductor using mode-matching method. The fields in each region were represented by either Floquet modes or waveguide modes. By applying tangential electric and magnetic field continuity conditions and using matrix equations, unknown coefficients and dispersion diagram were calculated. The proposed model can account for the effects of oblique incidence. Simulation time using the method was much faster than the commercial tools. We found that the current method produces accurate results of reflection phase and dispersion diagram.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.69-72
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• 2003

The meteorological model, CALMET, and its plume dispersion model, CALPUFF, were used in order to simulate the dispersion of $SO_2$ emitted from Yatagan Power Plant and its effect on Yatagan district in the episodic event on December 2 and 3, 2000. It is found that south westerly and light winds and the nighttime surface inversion layers lead to accumulation of pollutants over Yatagan district. The results are compared with the measurements done by Local Environmental Authorities of Mu la. The simulation results indicate that the maximum ground level concentrations were found northeast from the source, which agrees with experimental measurement. On the other hand, the magnitude of results obtained with the model shows some differences compared with experimental measurements.

• 물과 미래
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• 제23권2호
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• pp.213-225
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• 1990

본 연구는 불규칙한 단면을 가지면서 완곡을 이루는 일반하천에서 공장이나 가정으로부터 방류되는 오염물질의 횡확산현상을 예측하기 위한 수치모형을 제안하였다. 이 수치모형은 자연좌표계와 누적유량개념을 도입하였으며 여기에 필요한 여러가지 요소들을 직접측정하지 않고 컴퓨터 프로그래밍을 통하여 간단히 결과를 얻을수 있는 효율적인 방법을 개발하여 실험결과와 비교검토하므로서 본수치모형의 현지적용성을 검토하였다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.371-377
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• 2000

Environmental impact on a land reclamation project, Hwaong tidal barrier was studied using the dispersion and advection model to predict the influence of polluted water discharged from freshwater reservior. The simulation results show that the distribution of concentration by influence of polluted water discharged during a tidal cycle appeared to be extinguished at atmost all points after two tidal cycle. Peak concentration near the sluice gate is found out to be higher during the spring tide than neap tide. Equi-concentration contour line appeared to distributed a longer according to line of sea dike in spring tide than neap tide. The reasons is because influence by currents of northwest direction is a stronger, compared to spring tide and neap tide in the flood tide.

• 한국환경과학회지
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• 제14권6호
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• pp.577-582
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• 2005

Enormous apartment complexes in urban areas, temporary inversion state and heat island effect occur due to the strong sunshine and weak wind speeds which hinders the dispersion of air pollutants that are emitted from neighboring areas of apartment complexes. In this study, analysis were conducted by using the Fluent code based on the CFD(Computation Fluid Dynamics), including building layout, material, building height from the ground surface, the heat, analysis of flow field in the apartment complex. It was estimated that the temporal radiation inversion phenomenon during the daytime, which was caused by the weak wind speed and higher temperatures in the upper level, contributed to the stagnation of the air pollutants in the lower layer of the apartment complex.

• 반도체디스플레이기술학회지
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• 제18권4호
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• pp.62-68
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• 2019

The optoelectronic display units such as TFT-LCD or OLED require many thin optical plastic films and their mass manufacturing processes employ CO2 laser cutting of those thin films in a large quantity. However, laser film cutting could generate fume particles through melt shearing, vaporization, and chemical degradation and those particles could be of great concern for film surface contamination. In order to appreciate the fume particle dispersion behaviors in laser film cutting, this study relies on random particle simulations by probabilistic distributions of particle size, ejection velocity and angles coupled with Basset-Boussinesq-Oseen model of particle trajectory in low Reynolds number flows. Here, up to one million particles of random sampling have been tested to effectively show fume particles dispersed on the film surface. The computational results could show that particular range of fume particle size could easily disperse into the pixel region of processed optical films.

• Journal of the Optical Society of Korea
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• 제12권4호
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• pp.226-231
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• 2008

40 Gbps WDM Systems using super-Gaussian RZ pulses have been studied by numerical simulation to optimize their performance. The assumption of standard single mode fiber is valid when existing WDM systems are required to upgrade their performance to 40Gbps. It is shown that the standard single mode fiber can transmit optical signals over 720 km (Q > 10) by optimizing optical and electrical filter characteristics at the receiver and by compensation of dispersion. However, it is also shown that ${\pm}0.3%$ dispersion compensation tolerance per span (80 km) could prohibit transmitting over 320km (Q > 10). In addition, a duty cycle of less than 0.4 degrades system performance significantly.