Last Updated July 17, 2017

Formulation

When a contaminant enters the ground, the dissolved constituents will migrate due to the movement of the water. In addition, the contaminant disperses due to hydrodynamic mixing and molecular diffusion. The migration also may be retarded due to adsorption and radioactive decay. The advective-dispersive differential equation is derived by applying the principle of mass balance to an element of porous medium, with consideration of advection, dispersion, adsorption and decay.

CTRAN/W computes adsorption using the adsorption function and the computed nodal concentrations. It then computes the mass quantity in both the fluid phase and the solid phase.

CTRAN/W can also model contaminant movement by simply 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.

Features

  • Steady-state and transient water flow conditions through saturated and unsaturated soil systems.
  • Time-dependent hydraulic boundary conditions.
  • Anisotropic and heterogeneous ground conditions.
  • Time-dependent concentration and mass flux boundary conditions, free exit boundary conditions.
  • Molecular diffusion coefficient as a function of volumetric water content.
  • Model adsorption as a function of concentration, mass loss due to radioactive decay, and mass flux across user-specified sections.
  • Particle tracking isolates advection by showing the flow path of individual particles.
  • Density-dependent analysis with contaminant density different than groundwater density.
  • And many more!

Integration with Other Applications

Use SEEP/W or VADOSE/W velocities in CTRAN/W

One of the major components in a contaminant transport analysis is the velocity of the water, which can be obtained from a SEEP/W or VADOSE/W analysis. Once this velocity is known, it can be used in CTRAN/W to study the transport of contaminants.

Perform Density Dependent Analyses with CTRAN/W and SEEP/W

In density dependent fluid flow, the velocity of the water is dependent on the solute concentration. The water velocity in turn influences the movement of the solute. The iterative transfer of water velocity from SEEP/W to CTRAN/W and the transfer of concentration from CTRAN/W to SEEP/W makes it possible to do density dependant fluid flow analyses.

Engineering Methodology Book

The included CTRAN/W engineering methodology book discusses the whys and hows of modeling, as well as the theory and formulations behind the CTRAN/W product. Transport Modeling with CTRAN/W is a full-length book about proper modeling techniques: how to think before, during and after setting up and solving a model. The book includes chapters devoted to:
  • Material Properties
  • Bounday Conditions
  • Analysis Types
  • Functions in GeoStudio
  • Numerical Issues
  • Visualization of Results
  • Modeling Tips and Tricks
  • Illustrative Examples
  • Theory