Comparison of particle tracking algorithms in transient complex flow pattern

Heejun Suk 대한지질학회 2007 대한지질학회 학술대회 Vol.2007 No.0

Achieving Local Mass Conservation When Using Continuous Galerkin Finite Element Methods to Solve Solute Transport Equations With Spatially Variable Coefficients in a Transient State

Heejun Suk,Jui-sheng Chen,Seung Hyo Son,You Hong Kihm 한국방사성폐기물학회 2021 한국방사성폐기물학회 학술논문요약집 Vol.2021 No.11

New Analytical Solution of Multi-species Radionuclide Transport in Geological Barrier With Arbitrary Heterogeneous Aquifer

Heejun Suk,Jui-sheng Chen,Seung Hyo Son,You Hong Kihm 한국방사성폐기물학회 2021 한국방사성폐기물학회 학술논문요약집 Vol.2021 No.06

Development of Multiphase Flow Simulator Using the Fractional Flow Based Approach for Wettability Dependent NAPL Migration

Heejun Suk(석희준),In Wook Yeo(여인욱),Kang Kun Lee(이강근) 대한자원환경지질학회 2011 자원환경지질 Vol.44 No.2

The multiphase flow simulator, CHEMPS, was developed based on the fractional flow approach reported in the petroleum engineering literature considering fully three phase flow in physically and chemically heterogeneous media. It is a extension of MPS developed by Suk and Yeh (2008) to include the effect of wettability on the migration of NAPL. The fractional flow approach employs water, total liquid saturation and total pressure as the primary variables. Most existing models are limited to two-phase flow and specific boundary conditions when considering physically heterogeneous media. In addition, these models focused mainly on the water-wet media. However, in a real system, variations in wettability between water-wet and oil-wet media often occur. Furthermore, the wetting of porous media by oil can be heterogeneous, or fractional, rather than uniform due to the heterogeneous nature of the subsurface media and the factors that affect the wettability. Therefore, in this study, the chemically heterogeneous media considering fractional wettability as well as physically heterogeneous media were simulated using CHEMPS. In addition, the general boundary conditions were considered to be a combination of two types of boundaries of individual phases, flux-type and Dirichlet type boundaries. 석유공학분야에서 보고된 분율 흐름 접근 방식을 이용하여 물리적 또는 화학적으로 불균질한 매질에서 완전한 삼상유체 를 고려할 수 있는 다상 흐름 수치 모의 프로그램인 CHEMPS가 개발되었다. 이 프로그램은 석희준과 G.T. Yeh (2008)에 의해 개발된 MPS을 확장하였는데, 친수성이 NAPL 거동에 미치는 영향을 모의하기 위하여 개발되었다. 대부분 존재하는 모델들은 물리적으로 불균질한 매질을 고려하고 이상흐름과 특정한 경계조건에 국한되어 있다. 게다가 대부분의 모델들 은 주로 water-wet 매질에만 국한되어 있다. 그러나 실제 존재하는 시스템에서는, water-wet과 oil-wet 매질 사이의 친수 성의 변화는 종종 일어난다. 더군다나 기름에 의한 다공성 매질의 젖음은 균등하기 보다는 불균질 또는 부분적일 수 있 다. 왜냐하면 친수성에 영향을 미치는 요소들과 지하 매질이 불균질하기 때문이다. 따라서, 이번 연구에서는 물리적으로 불균질한 매질 뿐만 아니라 친수성 면에서 화학적으로 불균질한 매질을 CHEMPS을 활용하여 수치모의 하였다. 그 외에 도 개개의 상에 대해서 유량 경계조건 및 고정경계조건의 두 가지 형식의 결합으로 표현되는 일반경계조건이 고려되었다.

New semi-analytical solutions of the radial advection-dispersion equation for solute transport in divergent radial flow in a transient state

Heejun Suk,Jui-Sheng Chen,Seunghyo Son,You Hong Kihm 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10

Solute transport with the radial advection-dispersion in a radially convergent or divergent flow field is common phenomenon occurring in many applications such as aquifer decontamination, heat exchanges in geothermal exploration, and tracer tests. A lot of existing analytical solutions to the problem of tracer dispersion in such a radial flow are available. All these solutions take into account solute transport in a non-uniform flow from steady radial flow field created by injection or pumping wells. However, the non-uniform flow velocity is based on the Thiem equation and only spatially varying velocity. Despite strong field evidence that flow transients can be ubiquitous, previous analytical studies have assumed only steady-state groundwater flows. To our knowledge, the analytical solution to the radial advection dispersion equation in fully transient flow is not currently available. The purpose of this study is to develop a new semi-analytical solution for solute transport in a radially divergent flow in the fully transient state which doesn"t need any assumption on flow velocity. The proposed semi-analytical solution was verified against existing analytical solutions or numerical solution. In order to show how different concentration distribution or breakthrough curve in the transition flow is compared to in the steady flow, influences of the aquifer flow properties, solute transport parameters, and injection rate on discrepancies between the existing analytical solutions using the Thiem equation and the proposed semi-analytical solutions considering transient flow were investigated. The proposed solution shed light on emergence of new effective tracer test compared to traditional tracer test.

Numerical solution of the Kirchhoff-transformed Richards equation for simulating variably saturated flow in heterogeneous layered porous media

Suk, Heejun,Park, Eungyu Elsevier 2019 Journal of hydrology Vol.579 No.-

<P><B>Abstract</B></P> <P>A new numerical method was developed to accurately and efficiently compute a solution of the nonlinear Richards equation with a layered soil. In the proposed method, the Kirchhoff integral transformation was applied. However, in the Kirchhoff integral transformation approach, the transformed Kirchhoff head has dyadic characteristics at the material interface between different soil types. To avoid the dyadic characteristics at the material interface, a truncated Taylor series expansion was applied to the Kirchhoff head at the material interface and so the Kirchhoff head was replaced with a single pressure head value at the material interface. Accordingly, through the Taylor series expansion, a set of algebraic equations in the one-dimensional control volume finite difference discretized system formed a tridiagonal matrix system. Through a series of numerical experiments, the new method was compared to other numerical methods to determine its superiority. The results clearly demonstrated that the approach was not only more computationally efficient, but also more accurate and robust than other numerical methods. Computational performance was greatly enhanced with the proposed method, and which could be used to simulate complicated heterogeneous flow at a large-scale watershed or regional scale.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A numerical method is proposed to solve the Richards equation with a layered soil. </LI> <LI> Kirchhoff integral transformation is used to make a linearized governing equation. </LI> <LI> A Kirchhoff head at the interface is changed with a continuous pressure head. </LI> <LI> The method is more efficient, accurate, and robust than other numerical methods. </LI> </UL> </P>

실내모형시험과 수치해석을 통한 SVE의 효율성 평가

석희준(Suk Heejun),서민우(Seo Min Woo),고경석(Ko Kyung-Seok) 대한토목학회 2008 대한토목학회논문집 B Vol.28 No.1B

SVE 공법은 휘발성 유기물로 오염된 불포화대의 정화 공법으로 널리 적용되어 왔다. 본 연구에서는 SVE 적용시 오염물 제거 기작을 관찰하기 위해 모형조 시험을 수행하였으며, 이로부터 SVE 주요 특징인 tailing 현상, 즉 후반부로 갈수록 제거 속도가 급격히 느려지는 꼬리 효과를 확인하였다. 본 연구에서는 액상 막에서의 확산 제약 현상을 고려할 수 있는 수치 모델을 적용하였으며, 모형조 시험 결과와 구축된 수치 모델링을 통해 SVE의 전형적인 특징이 꼬리 현상을 적절하게 모사할 수 있었다. 또한 4가지 변수에 대한 민감도 분석을 수행하여, 총토양농도의 백분율은 액상확산계수가 클수록, 가스상 확산계수가 클수록, 실제확산경로가 짧을수록, 물포화도가 작을수록 빠르게 감소함을 확인하였다. Soil Vapor Extraction (SVE) has been extensively used to remove volatile organic compounds (VOCs) from the vadoze zone. In order to investigate the removal mechanism during SVE operation, laboratory modeling experiments were carried out and tailing effect could be observed in later stage of the experiment. Tailing effect means that removal rate of contaminants gets significantly to decrease in later stage of SVE operation. Also, mathematical model simulating the tailing effect was used, which considers rate-limited diffusion in a water film during mass transfer among gas, liquid, and solid phases. Measurement data obtained through the experiment was used as input data of the numerical analyses. Sensitivity analysis was performed to examine the effect of each parameter on required time to reach final target concentration. Finally, it was found that the concentration in the soil phase decreased significantly with a liquid and gas diffusion coefficient larger, actual path length shorter, and water saturation smaller.

기후변화대응 대용량지하수 확보 및 최적 활용 기술 개발

석희준(Heejun Suk),김용철(YongCheol Kim),고동찬(Dong-Chan Koh),이은희(Eunhee Lee),이수형(Soo-Hyoung Lee),김성균(Seong-Kyun Kim) 대한지질학회 2022 대한지질학회 학술대회 Vol.2022 No.10

Semi-analytical solution of land-derived solute transport under tidal fluctuation in a confined aquifer

Elsevier 2017 Journal of hydrology Vol.554 No.-

<P><B>Abstract</B></P> <P>A one-dimensional semi-analytical solution of land-derived solute transport, subject to tidal fluctuation in a coastal confined aquifer, was derived using the generalized integral-transform technique (GITT). To investigate the plume migration of land-derived contaminants within a tidally influenced aquifer, both spatially and temporally varying expressions of the Darcy velocity and dispersion coefficients obtained from the analytical solution of the groundwater head response, which were subject to sinusoidal boundary conditions due to tidal fluctuation, were considered. This new semi-analytical solution was verified against a numerical solution, as well as the peak location trajectory obtained using the Predictor-Corrector method. Sensitivity analyses of tidal amplitude, hydraulic conductivity, and storage coefficient using the proposed solution were performed to understand plume behavior with regard to plume shape, plume spatial moments, and macrodispersion coefficients to gain a better understanding of the transport mechanisms. As the tidal amplitude, hydraulic conductivity, and storage coefficient were increased, the peaks were travelled faster, and peak concentrations were decreased. In addition, an increase in tidal amplitude, hydraulic conductivity, and storage coefficient caused an increase in variance as well as the macrodispersion coefficient. It was observed that negative macrodispersion appeared when the storage coefficient was largest, as well as when the difference between landward-directed advective velocity at the leading and trailing edges of the plume was greatest. This newly developed semi-analytical solution provides a useful mathematical tool for validating numerical models and understanding the physical mechanism of the migration of plume discharge to the sea or estuaries within a tidally influenced aquifer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 1D semi-analytical solution for solute transport subject to tidal fluctuation. </LI> <LI> Spatially and temporally varying Darcy velocity and dispersion coefficient. </LI> <LI> A new semi-solution developed using GITT to validate numerical models. </LI> </UL> </P>

Modified Mixed Lagrangian–Eulerian Method Based on Numerical Framework of MT3DMS on Cauchy Boundary

Blackwell Publishing Ltd 2016 Ground Water Vol.54 No.4

<P><B>Abstract</B></P><P>MT3DMS, a modular three‐dimensional multispecies transport model, has long been a popular model in the groundwater field for simulating solute transport in the saturated zone. However, the method of characteristics (MOC), modified MOC (MMOC), and hybrid MOC (HMOC) included in MT3DMS did not treat Cauchy boundary conditions in a straightforward or rigorous manner, from a mathematical point of view. The MOC, MMOC, and HMOC regard the Cauchy boundary as a source condition. For the source, MOC, MMOC, and HMOC calculate the Lagrangian concentration by setting it equal to the cell concentration at an old time level. However, the above calculation is an approximate method because it does not involve backward tracking in MMOC and HMOC or allow performing forward tracking at the source cell in MOC. To circumvent this problem, a new scheme is proposed that avoids direct calculation of the Lagrangian concentration on the Cauchy boundary. The proposed method combines the numerical formulations of two different schemes, the finite element method (FEM) and the Eulerian–Lagrangian method (ELM), into one global matrix equation. This study demonstrates the limitation of all MT3DMS schemes, including MOC, MMOC, HMOC, and a third‐order total‐variation‐diminishing (TVD) scheme under Cauchy boundary conditions. By contrast, the proposed method always shows good agreement with the exact solution, regardless of the flow conditions. Finally, the successful application of the proposed method sheds light on the possible flexibility and capability of the MT3DMS to deal with the mass transport problems of all flow regimes.</P>