Unsaturated Flow and Advection-Dispersion in Three-Dimensionally Heterogeneous Geologic Media

1994 ◽  
pp. 415-422
Author(s):  
Amvrossios C. Bagtzoglou ◽  
Vivek Kapoor
Keyword(s):  
Unsaturated Flow ◽  
Advection Dispersion ◽  
Geologic Media

Transport of bacteria through geologic media

1996 ◽  
Vol 42 (4) ◽  
pp. 410-422 ◽  
Author(s):  
J. R. Lawrence ◽  
M. J. Hendry
Keyword(s):  
Ionic Strength ◽  
Model Development ◽  
Theoretical Development ◽  
Bacterial Transport ◽  
Confocal Laser ◽  
Column Studies ◽  
Advection Dispersion ◽  
And Behavior ◽  
Transport Of Bacteria ◽  
Geologic Media

A review of the current literature on transport of bacteria through geologic media is presented. The review addresses the major controls on bacterial transport. These controls include the nature of the substratum, the solute, and the bacterial cell. Most knowledge on the transport of bacteria through geologic media has been gained from column studies. There is need for some standardization of approaches, particularly with regard to data collection and controls on factors such as ionic strength and flow velocity. Other systems including glass micromodels have been used in conjunction with microscopy and scanning confocal laser microscopy to examine the controls on transport at the pore scale rather than porous medium scale of column studies. Many inconsistencies exist regarding the effect of the numerous variables that impact bacterial sorption in porous media. These variables include the nature of the substratum (i.e., the presence or absence of coatings), chemical composition of the solute (particularly ionic strength), system hydrodynamics, and bacterial variables such as size, shape, hydrophobicity, and electrostatic charge. Mathematical models based on the advective–dispersion equation have been developed to simulate bacterial transport. Within specific limits, these models can approximate most aspects of bacterial transport; however, they neglect parameters such as growth and behavior of bacteria. There is a need for theoretical development, extensive laboratory investigation, and model development before the goal of prediction of bacterial transport at field scale may be realized.Key words: sorption, advection, dispersion, models, facilitated transport.

Benchmark profiles for advection-dispersion migration of radionuclides through two-layered geologic media

1987 ◽  
Vol 5 (2) ◽  
pp. 87-103
Author(s):  
Shinichi Nakayama ◽  
Ikuji Takagi ◽  
Kunio Higashi
Keyword(s):  
Advection Dispersion ◽  
Geologic Media

Flow Through Heterogeneous Geologic Media

2015 ◽  
Author(s):  
Tian-Chyi Yeh ◽  
Raziuddin Khaleel ◽  
Kenneth C. Carroll
Keyword(s):  
Flow Through ◽  
Geologic Media

Parameter Determination for Chloride and Tritium Transport in Undisturbed Lysimeters during Steady Flow

1992 ◽  
Vol 23 (2) ◽  
pp. 89-104 ◽  
Author(s):  
Ole H. Jacobsen ◽  
Feike J. Leij ◽  
Martinus Th. van Genuchten
Keyword(s):  
Experimental Data ◽  
Unsaturated Flow ◽  
Transport Model ◽  
Time Moment ◽  
Breakthrough Curves ◽  
Coarse Sand ◽  
Retardation Factor ◽  
Parameter Determination ◽  
Model Parameters ◽  
Water Fraction

Breakthrough curves of Cl and 3H2O were obtained during steady unsaturated flow in five lysimeters containing an undisturbed coarse sand (Orthic Haplohumod). The experimental data were analyzed in terms of the classical two-parameter convection-dispersion equation and a four-parameter two-region type physical nonequilibrium solute transport model. Model parameters were obtained by both curve fitting and time moment analysis. The four-parameter model provided a much better fit to the data for three soil columns, but performed only slightly better for the two remaining columns. The retardation factor for Cl was about 10 % less than for 3H2O, indicating some anion exclusion. For the four-parameter model the average immobile water fraction was 0.14 and the Peclet numbers of the mobile region varied between 50 and 200. Time moments analysis proved to be a useful tool for quantifying the break through curve (BTC) although the moments were found to be sensitive to experimental scattering in the measured data at larger times. Also, fitted parameters described the experimental data better than moment generated parameter values.

Initial-boundary value problems for the one-dimensional linear advection–dispersion equation with decay

2020 ◽  
Vol 75 (8) ◽  
pp. 713-725 ◽  
Author(s):  
Guenbo Hwang
Keyword(s):  
Boundary Conditions ◽  
Dirichlet Boundary ◽  
Boundary Value ◽  
Initial Boundary ◽  
Initial Boundary Value Problems ◽  
One Dimensional ◽  
Advection Dispersion ◽  
Asymptotically Periodic ◽  
The One ◽  
Initial Boundary Value

AbstractInitial-boundary value problems for the one-dimensional linear advection–dispersion equation with decay (LAD) are studied by utilizing a unified method, known as the Fokas method. The method takes advantage of the spectral analysis of both parts of Lax pair and the global algebraic relation coupling all initial and boundary values. We present the explicit analytical solution of the LAD equation posed on the half line and a finite interval with general initial and boundary conditions. In addition, for the case of periodic boundary conditions, we show that the solution of the LAD equation is asymptotically t-periodic for large t if the Dirichlet boundary datum is periodic in t. Furthermore, it can be shown that if the Dirichlet boundary value is asymptotically periodic for large t, then so is the unknown Neumann boundary value, which is uniquely characterized in terms of the given asymptotically periodic Dirichlet boundary datum. The analytical predictions for large t are compared with numerical results showing the excellent agreement.

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