• Title/Summary/Keyword: advection-diffusion

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Analysis of Suspended Load using A Two-Dimensional Advection-Diffusion Equation in Coastal Zone (2차원 이송-확산 방정식을 이용한 해안에서의 부유사 해석)

  • Kang, Gyu-Young;Kim, Su-Jin;Cho, Yong-Sik
    • 한국방재학회:학술대회논문집
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    • 2007.02a
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    • pp.177-180
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    • 2007
  • Numerical simulations on the suspended load in the Do jang fish port are carried out. Suspended load is analysed by using the two-dimensional advection-diffusion equation. To describe behaviors of a pollutant in costal zone, a split-operator method is applied to the numerical model. The advection part is first solved by SOWMAC and then the diffusion part is solved by a three-level locally implicit scheme.

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The Role of Fronts on the Vertical Transport of Atmospheric Pollutants I: 2D frontal model experiment (대기오염물질의 연직 수송에 미치는 전선의 역할 I: 2차원 전선모델을 이용한 수송 실험)

  • Nam, Jae-Cheol;Thorpe, Alan
    • Atmosphere
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    • v.14 no.3
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    • pp.29-40
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    • 2004
  • It is well known that convections and fronts are the most effective weather systems for the vertical transport of pollutants. I used a two dimensional front model in order to investigate the mechanism of the vertical transport of atmospheric pollutants between planetary boundary layer(PBL) and free atmosphere by fronts. The main dynamic processes which contribute the vertical transport of pollutants are advection and diffusion. The transported amount of pollutant from the boundary layer to the free atmosphere increases dramatically during the developing stage of the front. 46% of pollutants are transported vertically within 12 hour and 54% are transported within 24 hour. In the meantime, compared to the total amount of pollutants transported by both advection and diffusion, about 25% (30%) less pollutants are transported when only advection (diffusion) process in included in the model. The most important mechanism for the vertical transport is vertical advection, while the vertical diffusion process plays an important role in the redistribution of pollutants in the PBL.

Behavior Characteristics of Density Currents Due to Salinity Differences in a 2-D Water Tank

  • Lee, Woo-Dong;Mizutani, Norimi;Hur, Dong-Soo
    • Journal of Ocean Engineering and Technology
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    • v.32 no.4
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    • pp.261-271
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    • 2018
  • In this study, a hydraulic model test, to which Particle Image Velocimetry (PIV) system applied, was used to determine the hydrodynamic characteristics of the advection-diffusion of saltwater according to bottom conditions (impermeable/permeability, diameter, and inclination) and the difference of the initial salt. Considering quantitative and qualitative results from the experiment, the characteristics of the density current were discussed. As an experimental result, the advection-diffusion mechanism of salinity was examined by the shape of saltwater wedge and the flow structure of density currents with various bottom conditions. The vertical salt concentration obtained from the experiment was used as quantitative data to calculate the diffusion coefficient that was used in the numerical model of the advection-diffusion of saltwater.

대기압의 변화에 따른 휘발성 오염물질의 토양에서 대기로의 거동

  • Choi Ji-Won;Smith James A.;Hwang Gyeong-Yeop
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2005.04a
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    • pp.114-116
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    • 2005
  • Natural attenuation has been actively studied and often selected as final clean-up process in remediation of contaminated ground-water and soil for the last decade. Accordingly, understanding of natural processes affecting the fate and transport of contaminants in the subsurface becomes important for a success of implementation of the natural remediation strategy, Contaminant advection and diffusion processes in the unsaturated zone are naturally related to environmental changes in the atmosphere. The atmospheric pressure changes affecting the transport of contaminants in the subsurface are investigated in this study. Moisture content, trichloroethylene (TCE) concentration, temperature, and pressure variations in the subsurface were measured for the July, August, November, and December 2001 at Picatinny Arsenal, New Jersey. These data were used for a one-phase flow and one-component transport model in simulating the soil-gas flow and accordingly the TCE transport in the subsurface in accordance with the atmosphere pressure variations at the surface. The soil-gas velocities during the sampling periods varied with a magnitude of $10^{-6}\;to\;10^{-7}\;m\;s^{-1}$ at land surface. The TCE advection fluxes at land surface were several orders of magnitude smaller than the TCE diffusion fluxes. A sensitivy analysis indicated that advection fluxes were more sensitive to changes in geo-environmental conditions compared to diffusion fluxes. Of all the parameters investigated in this study, moisture content has the most significant effect on TCE advection and diffusion fluxes.

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Numerical simulation of advection-diffusion on flow in waste stabilization ponds (1-dimension) with finite difference method forward time central space scheme

  • Putri, Gitta Agnes;Sunarsih, Sunarsih;Hariyanto, Susilo
    • Environmental Engineering Research
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    • v.23 no.4
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    • pp.442-448
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    • 2018
  • This paper presents the numerical simulation of advection-diffusion mechanism of BOD concentration which was used as an indicator of waste only in one flow-direction of waste stabilization ponds (1-dimension (1-D)). This model was represented in partial differential equation order 2. The purpose of this paper was to determine the simulation of the model 1-D of wastewater transport phenomena based advection-diffusion mechanism and did validate the model. Numerical methods which was used for the solution of this model is finite difference method with Forward Time Central Space scheme. The simulation results which was obtained would be compared with field observation data as a validation model. Collection of field data was carried out in the Wastewater Treatment Plant Sewon, Bantul, D.I. Yogyakarta. The results of numerical simulations were indicate that the advection-diffusion mechanism takes place continuously over time. Then validation of the model was state that there was a difference between the calculation results with the field data, with a correlation value of 0.998.

THE INSTABILITIES OF ACCRETION DISKS WITH RADIAL ADVECTION

  • WU XUE-BING
    • Journal of The Korean Astronomical Society
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    • v.29 no.spc1
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    • pp.231-232
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    • 1996
  • The local instabilities of accretion disks were extensively studied, with the considerations of radial advection, thermal diffusion and different disk geometry, dominated pressure and optical depth. Two inertial-acoustic modes in a geometrically thin, radiative cooling dominated disk depart from each other if very little advection is included. A geometrically slim, advection-dominated disk is found to be always stable if it is optically thin. However, if it is optically thick, the thermal diffusion has no effect on the stable viscous mode but has a significant contribution to enhance the thermal instability.

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RELATIONSHIPS AMONG CHARACTERISTIC FINITE ELEMENT METHODS FOR ADVECTION-DIFFUSION PROBLEMS

  • CHEN, ZHANGXIN
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.6 no.1
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    • pp.1-15
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    • 2002
  • Advection-dominated transport problems possess difficulties in the design of numerical methods for solving them. Because of the hyperbolic nature of advective transport, many characteristic numerical methods have been developed such as the classical characteristic method, the Eulerian-Lagrangian method, the transport diffusion method, the modified method of characteristics, the operator splitting method, the Eulerian-Lagrangian localized adjoint method, the characteristic mixed method, and the Eulerian-Lagrangian mixed discontinuous method. In this paper relationships among these characteristic methods are examined. In particular, we show that these sometimes diverse methods can be given a unified formulation. This paper focuses on characteristic finite element methods. Similar examination can be presented for characteristic finite difference methods.

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Numerical Simulation of Advection and Diffusion using the Local Wind Model in Pusan Coastal Area, Korea (부산 연안역에서의 국지풍모델을 이용한 이류확산 수치모의)

  • 김유근;이화운;전병일
    • Journal of Korean Society for Atmospheric Environment
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    • v.12 no.1
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    • pp.29-41
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    • 1996
  • The two-stage numerical model was used to study the relation between three-dimensional local wind model, advection/diffusion model of random walk method and second moment method on Pusan coastal area. The first stage is three dimensional time-dependent local wind model which gives the wind field and vertical dirrusion coefficient. The second stage is advection/diffusion model which uses the results of the first stage as input data. First, wind fields on Pusan coastal area for none synoptic scale wind showed typical land and sea breeze circulation, and convergence zone occured at 1200LST in northern of domain, in succession, moved northward of domain. Emissions from Sinpyeong industrial district were trasnported toward the inland by sea breeze during daytime, and reached the end part of domain about 1800LST. During nighttime, emissions return to sea by land breeze and vertical diffusion also contributes to upward transport. In order to use this model for forecast of air pollution concentration on the Pusan coastal area, it is necessary that computed value must be compared with measured value and wind fields model must also be dealt in detail.

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지하 하수터널 주변의 오염물 거동해석

  • 정일문;한일영;차성수
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2002.09a
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    • pp.327-330
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    • 2002
  • In this study, analyses of contaminant transport are peformed to evaluate the diffusion effect of A sewage tunnel. First, Crank's analytical method is used to measure the concentration change of contaminant with time and space. Two dimensional numerical analysis is performed to measure concentration distribution of contaminant. Both methods show that the diffusion effect is little even after 500 years. This means that when flow converges into the tunnel, the environmental effect of contaminant in tunnel is not serious because there is no advection occurs.

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BUBBLE STABILIZATION OF CHEBYSHEV-LEGENDRE HIGH-ORDER ELEMENT METHODS FOR THE ADVECTION-DIFFUSION EQUATION

  • Kim, Philsu;Kim, Sang Dong;Lee, Yong Hun
    • Bulletin of the Korean Mathematical Society
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    • v.53 no.2
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    • pp.423-440
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    • 2016
  • The bubble stabilization technique of Chebyshev-Legendre high-order element methods for one dimensional advection-diffusion equation is analyzed for the proposed scheme by Canuto and Puppo in [8]. We also analyze the finite element lower-order preconditioner for the proposed stabilized linear system. Further, the numerical results are provided to support the developed theories for the convergence and preconditioning.