CTRAN/W

Contaminant transport analysis

CTRAN/W models the movement of contaminants through porous materials such as soil and rock. CTRAN/W can be used to model simple diffusion-dominated systems through to complex advection-dispersion systems with first-order reactions.

CTRAN/W can be used to model a vast array of geo-environmental problems involving the movement of dissolved species that originate from either man-made or naturally occurring sources. 

Key Features

Comprehensive Formulation

CTRAN/W offers the capability to model a diverse set of contaminant transport mechanisms including diffusion, advection, dispersion, adsorption, decay, and density-dependant flow due to its comprehensive formulation.


Particle Tracking

CTRAN/W can model contaminant movement by tracking particles from user-defined locations. For each time step, CTRAN/W moves the particles a distance based on the volumetric water content and the SEEP/W-computed water velocities.

 


Saturated and Unsaturated

CTRAN/W is formulated for saturated and unsaturated transport, allowing the coefficient of diffusion to vary with water content and the advection process to adjust as groundwater velocities change in the unsaturated zone.

 


Model Sorption and Kinetic Reactions

CTRAN/W can model equilibrium sorption and first-order reactions such as radioactive decay, biodegradation, and hydrolysis.

 


CTRAN/W can model almost any contaminant transport problem

Download GeoStudio to view GSZ files

Caesium 137 Transport

Caesium-137 (Cs-137) is an anthropogenic radioactive isotope formed as a product of nuclear fission. The objective of this example is to analyze Cs-137 transport into an unconfined aquifer using CTRAN/W. The effect of adsorption and decay on solute concentrations and mass discharge is highlighted.

GSZ PDF

Henry Density

The results from a density-dependent CTRAN/W analysis are compared to the closed-form solution for the Henry saltwater intrusion problem (1964). The results from CTRAN/W compare well to the semi-analytical solution for both the standard and modified cases, which demonstrates the reliability of GeoStudio for modeling density-dependent transport problems.

GSZ PDF

Tailings Deposition

In this example saturated tailings are deposited with an initial concentration of 1.0 into a basin. A new layer is deposited every 20 days. With each new layer, the contaminants from the previous state become the starting condition for the new stage.

GSZ 

CTRAN/W Tutorial

The objective of this analysis is to demonstrate how CTRAN/W can be used to model solute transport by advection and dispersion. The analysis involves establishing the groundwater flow conditions and defining the appropriate material properties and boundary conditions. It also highlights the importance of selecting the correct solute boundary condition at the groundwater discharge location.

GSZ PDF

CTRAN/W's intuitive modeling workflow

Create a CTRAN/W analysis and set up the problem workspace. Choose analysis type from: advection-dispersion, density-dependent, or particle tracking (forward or backward). Define the initial pore-water pressure and concentration conditions, convergence criteria, and time duration and increments.

Draw the regions in your domain using CAD-like drawing tools, including drawing polygon and circular regions, coordinate import, copy-paste geometric items, length and angle feedback, region splitting and merging, and direct keyboard entry of coordinates, lengths, and angles. Alternatively, import AutoCAD DWG or DXF files directly into GeoStudio to create your domain geometry.

Define the material properties for your analysis, assign them to regions on the domain, and then define your initial concentration conditions. Define advection, dispersion or diffusion properties and add optional decay half-life. Define the initial seepage and concentration conditions for transient scenarios using results from other SEEP/W or CTRAN/W analyses or defined spatial functions.

Define concentration boundary conditions to simulate concentration, mass flux (q), mass rate (Q) or source concentration conditions. Time-varying conditions can also be modeled.

Open Draw Mesh Properties to refine the mesh drawn on the entire domain, or along specific geometric regions, lines or boundaries.

When your problem is completely defined, start the analysis process in the Solve Manager window. The Solve Manager displays the solution progress, allowing you to cancel if necessary. While the solution is in progress, you can look at preliminary results in the Results window.

When the Solver is finished, the concentration contours are displayed. Velocity vectors and the phreatic surface can also be viewed on the domain using results from the associated SEEP/W analysis. You can display other contours of almost any parameter including pore-water pressure, material properties, water flow, and gradients, using the Draw Contours window. Contour legends and properties can also be modified. Labels can be added to contour lines and flux sections for display in Results View. Flux section results can show total, advective, dispersive, stored or decayed flux. Particle tracking information is displayed and shading can be added for particle tracking analyses.

Interactively select any node or gauss region to view result information, including concentration, mass flux, material properties, and more. Display plots of computed results over the x- or y-direction or create time-varying plots of results in transient analyses, such as concentration, mass flux, cumulative mass and more. Generate reports of the definition and results, and export into other applications such as Microsoft Excel for further analysis.

The power of integration

CTRAN/W offers simple but powerful analytical capabilities when used in combination with other GeoStudio products.

CTRAN/W CTRAN/W

SEEP/W results in CTRAN/W

One of the major components of contaminant transport analysis is pore-water velocity, which can be simulated in SEEP/W. Combining CTRAN/W and SEEP/W analyses allows for a comprehensive assessment of contaminant transport in porous media.

Density-Dependent Flow

 

In density-dependent fluid flow, the solute concentration affects the density of water, which influences pore-water velocity. Meanwhile, pore-water velocity influences the movement of the solute and its concentration. Thus, SEEP/W and CTRAN/W analyses are interdependent in this case. The iterative transfer of information from SEEP/W to CTRAN/W, and vice versa, allows for the simulation of density-dependent fluid flow.


VADOSE/W results in CTRAN/W

Water velocities computed by a VADOSE/W land-climate interaction analysis can be used in CTRAN/W to study the transport of contaminants. For example, you could model the movement of salts into a reclamation cover overlying saline-sodic overburden waste.