## Getting Started with DuMux

### Running an example

For this example it is assumed that you followed the installation instructions and have a folder with a similar structure:

installation folder
|- dune-common
|- build-cmake
|- dune/common
|...
|- dune-geometry
|- build-cmake
|- dune/geometry
|...
|- dune-grid
|- dune-istl
|- dune-localfunctions
|- dumux
|- build-cmake
|- test
|- examples
|- dumux
|...
|- dumux
|...


We want to run an example, in which we first compute a single phase fluid flow field with heterogenous permeability field, and then run a tracer transport simulation with the computed velocity field. A detailed example description can be found here. First, we change to the example’s directory:

cd build-cmake/examples/1ptracer


We compile the example using GNU Make (this can take one minute):

make example_1ptracer


And finally we run the simulation:

./example_1ptracer


Besides console output, DuMux produces VTK output files that can be visualised with the open source visualisation tool Paraview.
This output is shown in the figure below:

### Changing runtime parameters

In the config file params.input, we can configure runtime parameters. Let us increase the end time TEnd of the simulation from 5000 to 7500 seconds.

[TimeLoop]
DtInitial = 10 # [s]
MaxTimeStepSize = 10
TEnd = 7500 # [s]


This results in the tracer travelling slightly further towards the upper end of the domain.

[TimeLoop] is a parameter group containing parameters configuring the time loop. The computational grid is configured in the [Grid] parameter group. UpperRight defines the size (x-, y-direction) of the area and Cells the number of cells in x- and y-direction, for a structured cube grid. If the parameter Grid.File is specified, the grid will be read from a grid file instead (we currently support Gmsh .msh, DUNE grid format .dgf and VTK files) In the parameter group [SpatialParams], we can define some spatially varying parameters. In this example, the parameter file is configured such that we can set the extent of a box-shaped lens (LensLowerLeft, LensUpperRight) with different permeability than the surrounding porous media. For example, we can decrease the size of the lens and observe how the resulting concentration field is influenced by the local permeability contrast.

[SpatialParams]
LensLowerLeft = 0.4 0.4
LensUpperRight = 0.6 0.6


We can see that this results in the tracer spreading more homogeneously in the domain.

For the purpose of developing your own application with DuMux , we recommend creating a separate DUNE module that lists DuMux as its dependency. DUNE provides a script, that creates such a new module. In your installation folder run:

./dune-common/bin/duneproject


Follow the instructions popping up, and enter:

• the name of your module (e.g. dumux-yourmodule)
• the module dependencies (enter dumux)
• version of your module (e.g. 0.1)

To configure your new module run dunecontrol:

./dune-common/bin/dunecontrol --opts=dumux/cmake.opts --only=dumux-yourmodule all


Now you can create your own test case. Enter the dumux-yourmodule folder and create a new folder (e.g. appl), that will contain your first test case.

mkdir appl


An easy and fast way to get the files for your test case is to copy an existing test from DuMux . We copy the following files from an incompressible single fluid phase flow model test application in dumux/test/porousmediumflow/1p/implicit/compressible/stationary:

• main.cc
• problem.hh
• spatialparams.hh
• params.input

To be able to configure and build your application with CMake, you need to first add the new appl subdirectory to the CMakeLists.txt file in dumux-yourmodule:

add_subdirectory(appl)


Inside the appl folder, create a new CMakeLists.txt and add the test case to it:

# add a new finite volume 1p test
SOURCES main.cc
COMPILE_DEFINITIONS TYPETAG=OnePCompressibleTpfa)

# add a symlink for the input file in the build folder


Now you need to reconfigure the module by typing (inside the folder dumux-yourmodule):

cmake build-cmake


As the last step, build and execute your new test case:

cd build-cmake
make build_tests
cd appl
./test_1p_compressible_stationary_tpfa params.input


This result visualized in with ParaView should look something like this:

### Next steps

To learn more about DuMux , we highly recommend the DuMux course. During the exercises you get a deeper insight into the structure of DuMux and its different applications. Futhermore, DuMux contains several documented example applications.