Model setup

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Model setup for fracture flow and transport in limestone aquifers - steps

This chapter gives step-by-step instructions for the setup of a model to simulate flow and transport in a fractured limestone aquifer. The following describes the typical steps to setup a model for contaminant transport in a fractured limestone aquifer:

Conceptualization and setup of a conceptual model including geology and hydrogeology

Geologic modeling

Boreholes can give valuable information about the geology. Bits of geologic knowledge can be connected to establish a geologic model, that shows different geologic layers, to which properties can be assigned, and other relevant geologic information. Example geologic profile of a Geoscene3D model.

Formulation of the modeling objectives

Choice of model complexity and modeling scale

Based on available data and modeling objectives, the model complexity has to be chosen. A very complex and detailed model is not appropriate if only little field data is available. Then, a simple model can be applied, which can be refined as soon as new data is measured.

The modeling was an integrated part of the limestone project. Initially, a rough model based on first measurements and available data was setup and then used to plan further field work and measurements.

The scale is also depending on the modeling objectives. Source zone remediation needs a different scale than the risk assessment of a contaminant plume for water works. The following scales can be considered:

  • well scale
  • source zone scale
  • intermediate scale for e.g. pumping tests
  • plume scale

Data acquisition - measurements to obtain relevant model parameters (see list of parameters for each model)

Delineation of the model domain based on physically meaningful boundaries (f.e. head isolines, no-flow boundaries)

Implementation of parameters for selected units in the model domain (homogeneous/heterogeneous)

Choice of boundary conditions for the flow and the transport model

Setup of sources and sinks: Definition of wells

For transient models: definition of initial conditions

Mesh generation: Start with coarse mesh, refine later

Simulation

Critical evaluation of the modeling results

Formulation of mass balances to check the model

Model calibration and validation

Model reporting

Flow chart giving an overview of the individual steps

ADD FLOW CHART

Example: Setup of models for a contaminated site with a fractured limestone aquifer (Akacievej, Hedehusene)

The setup of a discrete-fracture model in 2D in COMSOL Multiphysics is described in the following document:

The typical workflow for modeling a contaminated site will be demonstrated using an example field site close to Copenhagen.

Example: Setup of models for a field site (Akacievej, Hedehusene)

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