In the GWB, medium and fluid properties that can vary in space are known as field variables. Transient field variables can additionally be set to vary with time.

Field variables
Field variables

You can set heterogeneous values for the following variables in X1t and X2t models:

  • Composition and temperature of the initial fluid,
  • Groundwater flow field within the domain,
  • Amounts of reactant species, their cutoffs, and target activities and fugacities,
  • Kinetic rate law parameters, and
  • Single and dual porosity medium properties

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Setting field variables
Setting field variables

You set a field variable in various ways:

  • As a constant value,
  • As a random field with a Gaussian distribution,
  • As a table file, or in an in-line table,
  • Using a node-by-node editor, and
  • As the result of evaluating a character string, BASIC script, or compiled C/C++ function

X1t and X2t evaluate field variables at the onset of a run for each node in the domain.

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Transient field variables
Transient field variables

Transient variables are a special class of field variables that can vary both in space and in time. Options include:

  • Internal heat source and heat capacities of the fluid and rock,
  • Diffusion coefficient, dispersivities, thermal conductivity, and permeability coefficients,
  • Activation energies, pre-exponential factors, rate constants, specific surface areas, nucleation areas, and critical SI's for kinetic reactions,
  • Retardation factor, diffusion coefficient, and thermal conductivity of stagnant zones, and
  • Mobility of colloids

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Setting transient field variables
Mix reagents with fluids

Setting up transient field variables is similar to the procedure for specifying heterogeneous field variables or defining custom rate laws. For each transient field variable you need to:

  • Supply an equation, BASIC script, script file, or C/C++ function, and
  • Enable the “transient” option

React, Phase2, X1t, and X2t evaluate transient field variables at each nodal block upon undertaking each time step over the course of a run.

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Looking to model reactive transport in heterogeneous, evolving groundwater systems?

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