• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.369-383
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• 1993

An amended form of radiation stress is presented in the present model and the existence of the surface advection terms is verified through comparisons with wave energy equation. The model yields circulation patterns in both cross-shore and longshore directions on the plane beach slope. Comparison with laboratory experiments showed good agreements. Finally, a quasi-three dimensional model suitable for the entire nearshore zone is developed by linking the depth-integrated properties with vertical profiles.

• The KIPS Transactions:PartA
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• v.16A no.6
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• pp.419-426
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• 2009

To realistically simulate fluid, the Navier-Stokes equations are generally used. Solving these Navier-Stokes equations on the Eulerian framework, the non-linear advection terms invoke heavy computation and thus Semi-Lagrangian methods are used as an approximated way of solving them. In the Semi-Lagrangian methods, the locations of advection sources are traced and the physical values at the traced locations are interpolated. In the case of Stam's method, there are relatively many chances of numerical losses, and thus there have been efforts to correct these numerical errors. In most cases, they have focused on the numerical interpolation processes, even simultaneously using particle-based methods. In this paper, we propose a new approach to reduce the numerical losses, through improving the tracing method during the advection calculations, without any modifications on the Eulerian framework itself. In our method, we trace the grids with the velocities which will let themselves to be moved to the current target position, differently from the previous approaches, where velocities of the current target positions are used. From the intuitive point of view, we adopted the simple physical observation: the physical quantities at a specific position will be moved to the new location due to the current velocity. Our method shows reasonable reduction on the numerical losses during the smoke simulations, finally to achieve real-time processing even with enhanced realities.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.190-198
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• 2008

In this stduy, the column experiments were carried out assuming the soil was contaminated by leakage of gasoline containing MTBE from USTs and pipes around gas stations. Then, characteristics of MTBE transport in the soil were investigated using CXTFIT program. The column experiments with different soil properties, moisture content, organic matter content and flow rate were carried out. Some parameters(D, R, $\beta$, $\omega$) used in two-site non-equilibrium adsorption model were obtained from measuring the MTBE concentration in injection-liquid and in effluent and using CXTFIT program. In addition, The characteristics of MTBE transport in the soil was found using BTCs and obtained parameters. Consequently, the advection decreased as the increase of the content of fine particle and organic, while the MTBE transport by advection was enhanced as increasing flow rate and moisture content.

• Tunnel and Underground Space
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• v.9 no.4
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• pp.306-314
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• 1999

In underground spaces including nuclear waste repository, prediction of air quantity, temperature/humidity and pollutant concentration is utmost important for space construction and management during the normal state as well as for determining the measures in emergency cases such as underground fires. This study aims at developing a model for underground space environment which has capabilities to take into account the effects of autocompression for the natural ventilation head calculation, to find the optimal location and size of fans and regulators, to predict the temperature and humidity by calculating the convective heat transfer coefficient and the sensible and latent heat transfer rates, and to estimate the pollutant levels throughout the network. The temperature/humidity prediction model was applied to a military storage underground space and the relative differences of dry and wet temperatures were 1.5 ~ 2.9% and 0.6 ~ 6.1%, respectively. The convection-based pollutant transport model was applied to two different vehicle tunnels. Coefficients of turbulent diffusion due to the atmospheric turbulence were found to be 9.78 and 17.35$m^2$/s, but measurements of smoke and CO concentrations in a tunnel with high traffic density and under operation of ventilation equipment showed relative differences of 5.88 and 6.62% compared with estimates from the convection-based model. These findings indicate convection is the governing mechanism for pollutant diffusion in most of the tunnel-type spaces.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.4
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• pp.237-246
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• 2012

In this study, numerical model for transport of radionuclide and colloid was developed. In order to solve reaction-migration governing equation for colloid and radionuclide, Strang-splitting Sequential Non-Iterative (SNI), which is one of Operator Splitting Method, was used for numerical method and this was coded by MATLAB. From the verification by comparing the simulation results with analytical solution considering only solute transport and rock diffusion, the Pearson's correlation coefficient was greater than 0.99 which demonstrates the accuracy of the model.

• Journal of Ocean Engineering and Technology
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• v.9 no.1
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• pp.120-131
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• 1995

Numerical simulations on the suspended sediment transport in the Nakdong Estuary are carried out Uncoupled flow model and diffusion model of which the governing equations are two-dimensional depth integrated equations are used int his study. Four cases are tested in this numerical simulations in which the Gaduk waterway open boundary condition and Nakdong Estuary barrage boundary condition are considered as the boundary conditions. The simulated results are compared with the measured data which were obtained by NEDECO at hadan site on 1981.2.19. and by Dong-A university at one station in the study area on 1993.4.3. and show a good agreement with them. The construction of the Nakdong Estuary Barrage may affect to reduce the current near Jinudo an Daemadeung and the suspended sediment inflowed from the upstream in the wet season seems to be transported to the Dadae.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.01a
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• pp.345-348
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• 2022

본 논문에서는 유체 시뮬레이션(Fluid simulation)중 화염에서 표현되는 불똥 입자(Fire-flake particle)의 생성, 움직임과 삭제를 효율적으로 학습하고 표현할 수 있는 인공지능 기법에 대해 소개한다. 유체 시뮬레이션을 계산하기 위해서는 일반적으로 수치해석학과 같은 학문의 이해가 필요하며 불똥이나 거품과 같은 유체의 2차 효과(Secondary effect)는 기반유체(Underlying fluids)를 통해 추출되기 때문에 복잡하고 계산양이 많아진다. 이러한 문제를 완화하고자 본 논문에서는 인공신경망을 이용한 분류 모델 학습을 통해 격자 내에서 표현되어야 하는 불똥 입자의 생성을 학습하고, 다항 회귀 모델 학습을 통해 불똥 입자의 움직임을 예측한다. 또한, 불똥 입자가 삭제되어야하는 상태를 네트워크 학습을 통해 얻어내며, 수명(Lifespan) 임계값 조절하여 다양한 장면에서 불똥을 제어할 수 있다. 결과적으로 화염의 움직임을 기반으로 불똥의 움직임을 복잡한 수학식이나 디자이너에게 의존하지 않고 인공지능 학습을 통해 쉽게 제어하고 예측하는 결과를 보여준다.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.442-442
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• 2022

고해상도 시공간적 격자 형태의 레이더 강수는 돌발홍수(flash flood)와 같은 기상재해에 대비하기 위하여 실시간 예측정보로 활용된다. 그러나 대부분의 레이더 강수는 과소 추정되는 경향이 있어 정량적인 보정 과정인 QPE (Quantitative Precipitation Estimation)가 필요하다. 일반적으로 레이더 강수자료 보정은 지점 관측자료를 활용하지만, 본 연구에서는 지상 강수량 기반의 고해상도 격자 강수자료를 생산하여 레이더 강수자료와 직접적으로 비교하고자 한다. 이에 고도와 지형적 특성을 고려한 PRISM(Precipitation-elevation Regressions on Independent Slopes Model) 방법을 사용하여 고해상도 격자기반의 자료를 생성하였다. PRISM 방법은 고도와 지리정보를 독립변수로 갖는 회귀모형 기반의 기후인자 추정 모형이다. 생산된 고해상도 격자 강수자료와 레이더 강수자료를 QPF (Quantitative Precipitation Forecast) 모델의 입력자료로 사용하여 예측결과를 비교하였다. 해당 QPF 모델은 이류(advection)와 확률론적 섭동(stochastic perturbation)을 기반으로 하며, 강수 앙상블 자료를 생산한다. QPF 모델에 대해 투 트랙(two-track) 방법으로 생산된 예측정보를 통해 레이더 강수자료의 격자별 후처리 보정이 가능할 것으로 판단된다.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.10
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• pp.1090-1098
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• 2005

Benzoyl peroxide is very toxic to aquatic organisms but environmental concentration or exposure effects were not studied. Distribution of the chemical among multimedia environment was estimated using EQC(Equilibrium Criterion) model based on the physical-chemical properties to evaluate the risk of benzoyl peroxide in environment. Level I describes a situation that 100,000 kg of benzoyl peroxide is emitted into the environment which is equilibrium and steady-state without degradation and advection condition. Level II describes a situation that a constant rate of 1,000kg/h of benzoyl peroxide is continuously discharged into the environment which is equilibrium and steady-state with degradation and advection condition. Level III describes a situation that 1,000 kg/h of benzoyl peroxide is continuously introduced in each air, water, soil, and sediment compartment which are non-equilibrium and steady-state with degradation, advection, and inter-media transfer condition. In Level I and II calculations the chemical was distributed to soil(68.3%) and water(28.7%). In Level III calculation it was primarily distributed to soil(99.9%) and overall residence time was estimated to be 3.4 years. Benzoyl peroxide can be persistent in environment.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.341-341
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• 2020

서울시는 '10년, '11년, '18년의 기록적인 호우로 인해 막대한 재산피해를 기록하였다. 이로 인해 서울시는 수재해 최소화 대책의 필요성을 인지하여 방재시설물 확충 등의 구조적 대책과 함께 침수지역 예측, 호우 영향 예보와 관련된 비구조적 대책 수립을 위해 노력하고 있다. 그 일환으로 '18년에 『서울시 강한 비구름 유입경로 및 침수위험도 예측 용역』을 수행하였으며 이를 통해 레이더 기반의 비구름 이동경로 추정 기술, 침수시나리오 기반의 침수위험지역 추정기술 등을 적용한 서울시 도시침수 예측시스템을 개발하였다. 그러나 침수피해에 선제적으로 대응하기 위해서는 실시간으로 예측강우정보를 생산하고 이를 통해 침수위험지역을 추정하는 기술이 필요하다. 이에 본 연구를 통해 예측강우정보 생산 기술 적용, 예측강우정보를 이용한 실시간 침수위험지역 추정 기술 개발을 수행하여 서울시 도시침수 예측시스템을 고도화하였다. 예측강우정보의 경우 현재 기상청에서 광역 단위 호우특보 및 읍면동 단위 동네예보를 통해 제공되고 있지만, 풍수해 업무에 적용하기에는 제한적이며, 실시간 침수위험지역 추정의 경우 침수해석모델의 모의시간, 라이센스 등의 문제로 인해 한계를 보이고 있는 실정이다. 따라서 본 연구에서는 레이더 실황강우정보를 활용한 이류모델 기반의 예측강우정보 생산 기술을 적용하여 풍수해 업무 적용이 용이하도록 하였으며, 예측강우정보를 이용한 최적 침수시나리오 추정 기술 개발을 통해 실시간 침수위험지역 추정이 가능하도록 하였다. 서울시 도시침수 예측시스템은 25개 자치구를 대상으로 강우량, 호우이동경로, 침수 정보를 제공하고 있다. 강우정보는 기상청 및 SK-TechX 기반의 10분 및 1시간 단위 AWS 관측정보, 이류모델 기반 10분 단위 레이더 예측정보, 국지예보모델 기반 1시간 단위 LDAPS 예측정보를 제공하며. 호우이동경로는 레이더 실황강우정보와 LDAPS 바람장을 이용하여 서울시 및 수도권 지역의 10분 단위 1시간 예측경로를 제공한다. 침수정보는 실시간으로 레이더 예측강우정보를 이용하여 최적의 침수시나리오를 추정하여 격자 단위 상세 침수정보와 시군구 단위 침수위험지도를 제공한다. 본 시스템을 통해 실시간 침수위험지역 확인이 가능해짐에 따라 서울시의 효율적인 풍수해 업무 지원이 가능할 것으로 판단된다.