• 제목/요약/키워드: multi-species transport

검색결과 27건 처리시간 0.02초

다양한 경계조건을 가진 일차 반응 네트워크로 결합된 다종 오염물 거동 해석해 (Analytical Solution of Multi-species Transport Equations Coupled with a First-order Reaction Network Under Various Boundary Conditions)

  • 석희준;채병곤
    • 한국지하수토양환경학회지:지하수토양환경
    • /
    • 제16권6호
    • /
    • pp.46-57
    • /
    • 2011
  • In this study, analytical solution of multip-species transport equations coupled with a first-order reaction network under constant concentration boundary condition or total flux boundary condition is obtained using similarity transformation approach of Clement et al. (2000). The study shows the schematic process about how multi-species transport equations with first-order sequential reaction network is transformed through the similarity transformation approach into independent and uncoupled single species transport equations with first-order reaction. The analytical solution was verified through the comparison with popular commercial programs such as 2DFATMIC and RT3D. The analytical solution can be utilized in nuclear waste sites where radioactive contaminants and their daughter products occur and in industrial complex cities where chlorinated solvent such as PCE, TCE, and its biodegradation products produces. In addition, it can help the verification of the developed numerical code.

다중상 흐름과 다종성분의 거동에 관한 수치적 모의와 문제점 (Numerical simulations and related problems in multiphase flow and multicomponent transport)

  • 이강근;이진용;천정용;유동렬;하규철;이철효
    • 한국지하수토양환경학회:학술대회논문집
    • /
    • 한국지하수토양환경학회 1998년도 공동 심포지엄 및 추계학술발표회
    • /
    • pp.27-31
    • /
    • 1998
  • Most models for the simulation of multi-phase flow and multi-species transport employ the capillary approach which uses the Darcy's law for the representation of mass flux of each phase. The capillary approach based on the Darcy's law require many empirical coefficients with complex functional dependencies rather than rigrous mathematical and physical formulation. The shortcoming of the capillary approach cause the numerical errors in the simulations by the multi-phase flow and transport models. This study discuss some of the problems related with the use of models.

  • PDF

ANALYSIS OF TWOPHASE FLOW MODEL EQUATIONS

  • Jin, Hyeonseong
    • 호남수학학술지
    • /
    • 제36권1호
    • /
    • pp.11-27
    • /
    • 2014
  • In this paper, we propose closures for multi-phase flow models, which satisfy boundary conditions and conservation constraints. The models governing the evolution of the fluid mixing are derived by applying an ensemble averaging procedure to the microphysical equations characterized by distinct phases. We consider compressible multi species multi-phase flow with surface tension and transport.

Temperature effect on multi-ionic species diffusion in saturated concrete

  • Damrongwiriyanupap, Nattapong;Li, Linyuan;Limkatanyu, Suchart;Xi, Yunping
    • Computers and Concrete
    • /
    • 제13권2호
    • /
    • pp.149-171
    • /
    • 2014
  • This study presents the mathematical model for predicting chloride penetration into saturated concrete under non-isothermal condition. The model considers not only diffusion mechanism but also migration process of chloride ions and other chemical species in concrete pore solution such as sodium, potassium, and hydroxyl ions. The coupled multi-ionic transport in concrete is described by the Nernst-Planck equation associated with electro-neutrality condition. The coupling parameter taken into account the effect of temperature on ion diffusion obtained from available test data is proposed and explicitly incorporated in the governing equations. The coupled transport equations are solved using the finite element method. The numerical results are validated with available experimental data and the comparison shows a good agreement.

Prediction of chloride ingress into saturated concrete on the basis of a multi-species model by numerical calculations

  • Nguyen, T.Q.;Baroghel-Bouny, V.;Dangla, P.
    • Computers and Concrete
    • /
    • 제3권6호
    • /
    • pp.401-422
    • /
    • 2006
  • A multi-species model based on the Nernst-Planck equation has been developed by using a finite volume method. The model makes it possible to simulate transport due to an electrical field or by diffusion and to predict chloride penetration through water saturated concrete. The model is used in this paper to assess and analyse chloride diffusion coefficients and chloride binding isotherms. The experimental assessment of the effective chloride diffusion coefficient consists in measuring the chloride penetration depth by using a colorimetric method. The effective diffusion coefficient determined numerically allows to correctly reproduce the chloride penetration depth measured experimentally. Then, a new approach for the determination of chloride binding, based on non-steady state diffusion tests, is proposed. The binding isotherm is identified by a numerical inverse method from a single experimental total chloride concentration profile obtained at a given exposure time and from Freundlich's formula. In order to determine the initial pore solution composition (required as initial conditions for the model), the method of Taylor that describes the release of alkalis from cement and alkali sorption by the hydration products is used here. Finally, with these input data, prediction of total and water-soluble chloride concentration profiles has been performed. The method is validated by comparing the results of numerical simulations to experimental results obtained on various types of concretes and under different exposure conditions.

전산 유체 해석에 의한 자동차 운반선 내부 환기 시스템 평가 (Assessment of Ventilation System for Ro/Ro Ship Using CFD)

  • 이승수;김학선;천승현
    • 대한조선학회논문집
    • /
    • 제42권1호
    • /
    • pp.10-17
    • /
    • 2005
  • Due to emission of vehicles during loading/unloading, ventilation system in Roll-on/Roll-off ship is inevitable; however it is very difficult to predict the ventilation performance before it is finally built in. Although the requirements for the ventilation system include air change rate and maximum allowable concentration of CO in the cargo holds, even prototype tests are hardly able to quantify the ventilation performance. In the present paper, a new method to assess the ventilation performance of Roll-on/Roll-off ship is proposed by using computational fluid dynamics. The air exchange is modeled by introducing multi-species transport of existing air In the holds and new air from the ventilation system. Conservation of multi-species as well as 3D Navier-Stokes equation are solved numerically in time dependent manner. Several cases of different configuration are considered. The results include predicted mass fraction of new air in the holds. It is also presented that CO concentration can be estimated based on the predicted air change performance. Due to the lack of experimental data, the computed results are not verified; however the proposed method can be applied as au assessment tool.

Coupled diffusion of multi-component chemicals in non-saturated concrete

  • Damrongwiriyanupap, Nattapong;Li, Linyuan;Xi, Yunping
    • Computers and Concrete
    • /
    • 제11권3호
    • /
    • pp.201-222
    • /
    • 2013
  • A comprehensive simulation model for the transport process of fully coupled moisture and multi-species in non-saturated concrete structures is proposed. The governing equations of moisture and ion diffusion are formulated based on Fick's law and the Nernst-Planck equation, respectively. The governing equations are modified by explicitly including the coupling terms corresponding to the coupled mechanisms. The ionic interaction-induced electrostatic potential is described by electroneutrality condition. The model takes into account the two-way coupled effect of moisture diffusion and ion transport in concrete. The coupling parameters are evaluated based on the available experimental data and incorporated in the governing equations. Differing from previous researches, the material parameters related to moisture diffusion and ion transport in concrete are considered not to be constant numbers and characterized by the material models that account for the concrete mix design parameters and age of concrete. Then, the material models are included in the numerical analysis and the governing equations are solved by using finite element method. The numerical results obtained from the present model agree very well with available test data. Thus, the model can predict satisfactorily the ingress of deicing salts into non-saturated concrete.

새만금호 3차원 수리.수질모델(EFDC)의 수치격자 민감도 분석 (A Sensitivity Analysis on Numerical Grid Size of a Three-Dimensional Hydrodynamic and Water Quality Model (EFDC) for the Saemangeum Reservoir)

  • 전지혜;정세웅
    • 한국물환경학회지
    • /
    • 제28권1호
    • /
    • pp.26-37
    • /
    • 2012
  • Multi-dimensional hydrodynamic and water quality models are widely used to simulate the physical and biogeochemical processes in the surface water systems such as reservoirs and estuaries. Most of the models have adopted the Eulerian grid modeling framework, mainly because it can reasonably simulate physical dynamics and chemical species concentrations throughout the entire model domain. Determining the optimum grid cell size is important when using the Eulerian grid-based three-dimensional water quality models because the characteristics of species are assumed uniform in each of the grid cells and chemical species are represented by concentration (mass per volume). The objective of this study was to examine the effect of grid-size of a three dimensional hydrodynamic and water quality model (EFDC) on hydrodynamics and mass transport in the Saemangeum Reservoir. Three grid resolutions, respectively representing coarse (CG), medium (MG), and fine (FG) grid cell sizes, were used for a sensitivity analysis. The simulation results of numerical tracer showed that the grid resolution affects on the flow path, mass transport, and mixing zone of upstream inflow, and results in a bias of temporal and spatial distribution of the tracer. With the CG, in particular, the model overestimates diffusion in the mixing zone, and fails to identify the gradient of concentrations between the inflow and the ambient water.

저 유전 재료의 에칭 공정을 위한 $H_2/N_2$ 가스를 이용한 Capacitively Coupled Plasma 시뮬레이션 (Capacitively Coupled Plasma Simulation for Low-k Materials Etching Process Using $H_2/N_2$ gas)

  • 손채화
    • 대한전기학회논문지:전기물성ㆍ응용부문C
    • /
    • 제55권12호
    • /
    • pp.601-605
    • /
    • 2006
  • The resistance-capacitance (RC) delay of signals through interconnection materials becomes a big hurdle for high speed operation of semiconductors which contain multi-layer interconnections in smaller scales with higher integration density. Low-k materials are applied to the inter-metal dielectric (IMD) materials in order to overcome the RC delay. Relaxation continuum (RCT) model that includes neutral-species transport model have developed to model the etching process in a capacitively coupled plasma (CCP) device. We present the parametric study of the modeling results of a two-frequency capacitively coupled plasma (2f-CCP) with $N_2/H_2$ gas mixture that is known as promising one for organic low-k materials etching. For the etching of low-k materials by $N_2/H_2$ plasma, N and H atoms have a big influence on the materials. Moreover the distributions of excited neutral species influence the plasma density and profile. We include the neutral transport model as well as plasma one in the calculation. The plasma and neutrals are calculated self-consistently by iterating the simulation of both species till a spatio-temporal steady state profile could be obtained.

FGM기반 Multi-Environment PDF 모델을 이용한 메탄/공기 부상화염장의 Large Eddy Simulation (Large Eddy Simulation of a Lifted Methane/Air Flame using FGM-based Multi-Environment PDF Approach)

  • 김남수;김재현;김용모
    • 한국연소학회:학술대회논문집
    • /
    • 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
    • /
    • pp.265-266
    • /
    • 2015
  • The multi-environment PDF model coupled with flamelet generated manifolds(FGM) has been developed for a large eddy simulation of turbulent partially premixed lifted flame. This approach has a capability to realistically account for the transport and evolution of probability density function for mixture fraction and progress variable with the manageable computational burden. Using the tabulated chemistry, it is possible to track radical distributions which is important to predict autoignition process with the vitiated coflow environment. Numerical results indicate that the present yields the good agreement with experimental data in terms of mixture fraction, temperature, and species mass fractions.

  • PDF