• 한국군사과학기술학회지
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• 제11권3호
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• pp.169-175
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• 2008

A fine carbon fibers dispersion model is implemented to calculate the scattering range and ground level concentration of carbon fibers emitted at certain altitudes of atmospheric boundary layer. This carbon fibers dispersion model was composed by coupling a commonly used atmospheric dispersion model and an atmospheric boundary layer model. The atmospheric boundary layer model, applying the Monin-Obukov Similarity Rule obtained from measurement input data at ground level, was used to create the atmospheric boundary layer structure. In the atmospheric dispersion model, the Lagrangian Particle Model and the Markov Process were applied to calculate the trajectory of scattered carbon fibers relative to gravity and aerodynamic force, as well as carbon fibers specification.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.433-436
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• 2006

In this study we perform Lagrangian stochastic model simulation for heavy particle. Reynolds(2002) construct simple LSM for heavy particle, which lack in detailed parameter study and statistics of turbulent flow within his paper. we investigate more simple but important turbulent statistics such as autocorrelation for velocity and acceleration, Lagrangian structure function and dispersion statistics parameterized by using DNS.

• 한국해안해양공학회지
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• 제10권2호
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• pp.73-82
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• 1998

연안에서 표층 방류된 온수의 확산-이송을 모의하고자 배출구 인근의 근역에서는 반능동적 입자추적의 원리가 적용된 부작위행보모형과 원역에서는 Eulerian-Lagrangian 농도가 결합된 2차원 모형이 개발되었다. 근역에서 표층으로 부상되는 온수괴는 부력을 갖는 다수의 입자군으로 변환되어 초기 평면확산의 증가를 나타내고, 이러한 부력확산의 영향이 무작위행보의 기본식에 도입되었다. 개발된 모형의 초기평가는 단순한 지형의 해역과 실제해역에서 수행되었다. 단순해역에서는 부력이 고려되지 않는 중립입자모형의 결과에 비하여 초기 확산이 크게 나타나고, 기존 근역모형CORMIX3과 유사하나 외해측으로 확장된 성향을 보인다. 천수만에서 실제적용 결과도 배출구 근처에서 관측치에 유사한 퍼짐 효과가 나타나며 모형의 적용성이 인정된다.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2000년도 춘계학술대회 논문집
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• pp.167-168
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• 2000

복잡한 구조를 갖고 시간에 따라서 변하는 바람장내에서 공장굴뚝과 같은 점오염원에서 배출되는 오염물질의 확산을 계산하기 위해서 라그란지안 입자확산모텔(Lagrangian Particle Dispersion Model, LPDM)을 사용하는 것이 최근의 연구 동향이다. 구윤서(1999a, 1999b)는 중립 및 안정한 대기조건에서 바람장 계산시 비평형 2.5 난류모델을 이용한 LPDM을 개발하여 복잡한 대기흐름내 확산현상을 보다 정확히 모사할 수 있는 LPDM을 제시하였다. (중략)

• 한국대기환경학회지
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• 제15권6호
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• pp.767-777
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• 1999

In the coastal region air flow changes due to the abrupt change of surface temperature between land and sea. So a numerical simulation for atmospheric flow fields must be considered the correct fields of sea surface temperature(SST). In this study, we used variables such as latent heat flux, sensible heat flux, short and long wave radiation of ocean and atmosphere which exchanged across the sea surface between atmosphere and ocean model. We found that this consideration simulated the more precise SST fields by comparing with those of the observated results. Simulated horizontal SST differences in season were 2.5~4$^{\circ}C$. Therefore we simulated the more precise atmospheric flow fields and the movement and dispersion of the pollutants with the Lagrangian particle dispersion model. In the daytime dispersion pattern of the pollutants emitted from ship sources moved toward inland, in the night time moved toward sea by land/sea breeze criculation. But air pollutants dispersion can be affected by inland topography, especially Yangsan and coastal area because of nocturnal wind speed decrease.

• 대한기계학회논문집
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• 제15권1호
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• pp.241-251
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• 1991

본 연구에서는 이런 점들을 고려, 난류유동장 내의 실제 입자운동을 좀더 사 실에 가깝도록 해석할 수 있는 모델을 제시하여 아직 실험에 의존하고 있는 관계분야 에 그 이론적 응용범위를 넓히는데 그 목적을 두었따. 본 연구의 목적상 입자가 존 재하는 난류장의 통계적 특성은 이미 알고 있는 것으로 가장하였으며 유체 내의 입자 농도가 충분히 낮고 입자의 크기가 충분히 작아서 입자가 유동장에 미치는 영향은 무 시할 수 있다고 간주하였다.

• 한국대기환경학회지
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• 제22권1호
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• pp.73-84
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• 2006

Hazardous Air Pollutants (HAPs) are characterized by being relatively heavier and denser than that of ambient air due to the various reasons such as higher molecular weight, low temperature and other complicated chemical transformations (Witlox, 1994). In an effort to investigate transport and diffusion from instantaneous emission of heavy gas, Lagrangian Particle Dispersion Model (LPDM) coupled with the RAMS output was employed. Both deposition process and buoyancy term were added on the atmospheric diffusion equations of LPDM, and the locations and concentrations of dense gas particle released from instantaneous single point source (emitting initially for 10 minutes only) were analyzed. The result overall shows that adding deposition process and buoyancy terms on the diffusion equation of LPDM has very small but detectable effect on the vertical and horizontal distribution of Lagrangian particles that especially transported for a fairly long traveling time. Also the slumping of dense gas can be found to be ignored horizontally compared to the advection by the horizontal wind suggesting that it was essential to couple the Lagrangian particle dispersion model coupled with the RAMS model in order to explain the dispersion of HAPs more accurately. However, during the initial time of instantaneous emission, buoyancy term play an important role on the vertical locations of dense particles for near surface atmosphere and around source area, indicating the importance of densities of HAPs in the beginning stage or short duration for the risk assessment of HAPs or management of heavy vapors during the explosive accidents.

• 한국해안해양공학회지
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• 제8권2호
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• pp.185-192
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• 1996

연안에서의 효율적인 확산해석을 위해 연산자 분리기법에 의한 Eulerian-Lagrangian 농도모형과 random walk 방법이 결합된 모형이 수립되었다 수립한 입자추적모형은 특히 고농도 변화 지역에서 오차 없이 만족스럽게 해석할 수 있는 수단으로 판단된다. 모형실험결과 오염원 방류초기의 ▽C$\geq$0.005에서 거의 정확해와 일치하는 결과를 얻었고, ▽C$\leq$0.002에서는 만족스럽지 못한 결과가 유도되어 입자추적모형의 적용한계의 기준으로 제시되었다. 따라서 실제 해역에서의 적용에서 고농도의 오염원이 발생되는 근역에서는 입자추적모형을 적용하고 이후의 전역에 대해서는 농도모형을 이용하여 해석상의 능률 제고와 정도의 향상을 도모할 수 있었다.

• 해양환경안전학회지
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• 제3권1호
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• pp.73-83
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• 1997

To predict the oil-spill dispersion in marine waters, the oil-spill dispersion model based on Lagrangian particle-tracking method was developed and applied to Kwangyang and Jinju Bay. The tidal current movements to be required as input data of the oil-spill dispersion model were obtained by a two-dimensional numerical tidal model. Evaluation of tidal current movements using mean tide was successful. Modelling results were compared with the field data obtained at spill site. There were some descrepancies between modeling results and field data. However, the general pattern of modelling results was similar to that of field data. Provided the real-time tidal currents and more accurate wind data are supported, more favorable results can be obtained.

• 대기
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• 제29권5호
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• pp.551-566
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• 2019

Quantitative understanding of a random error that is associated with Lagrangian particle dispersion modeling is a prerequisite for backward-in-time mode simulations. This study aims to quantify the random error of the WRF-FLEXPART model and suggest an optimum number of the Lagrangian particles for backward-in-time simulations over the Seoul metropolitan area. A series of backward-in-time simulations of the WRF-FLEXPART model has conducted at two receptor points by changing the number of Lagrangian particles and the relative error, as a quantitative indicator of random error, is analyzed to determine the optimum number of the release particles. The results show that in the Seoul metropolitan area a 1-day Lagrangian transport contributes 80~90% in residence time and ~100% in atmospheric enhancement of carbon monoxide. The relative errors in both the residence time and the atmospheric concentration enhancement are larger when the particles release in the daytime than in the nighttime, and in the inland area than in the coastal area. The sensitivity simulations reveal that the relative errors decrease with increasing the number of Lagrangian particles. The use of small number of Lagrangian particles caused significant random errors, which is attributed to the random number sampling process. For the particle number of 6000, the relative error in the atmospheric concentration enhancement is estimated as -6% ± 10% with reduction of computational time to 21% ± 7% on average. This study emphasizes the importance of quantitative analyses of the random errors in interpreting backward-in-time simulations of the WRF-FLEXPART model and in determining the number of Lagrangian particles as well.