Exercise 2

Ok, time to put our new knowledge to work! Let’s explore a more realistic case and investigate how a more permeable fault zone can deviate hydrothermal upflow. You can find background on such a setup in [Andersen et al., 2015].

Steps

• check all settings and modify model run time so that the plume arrives at the surface

• modify (or create) a setFieldsDict to create the permeability structure.

• use a function called rotatedBoxToCell to set the permeability structure

• run the case and explore how the results change for different fault widths and permeability contrasts.

Step 1

Copy the $HOME/hydrothermalfoam-master/cookbooks/2d/Regular2DBox/ into your working directory.

cd $HOME/HydrothermalFoam_runs
cp -r /home/openfoam/hydrothermalfoam-master/cookbooks/2d/Regular2DBox/ ./Fault_zone_2D

Step 2

Now modify the case and setup the permeability structure. It should look like this:

Fig. 37 Permeability structure of our detachment fault example cause.

We can use the rotatedBoxToCell function in the setFieldsDict for this. Check the openfoam documentation !

Tip

It’s all about rotating the coordinate system to figure out the origin and i,j,k vectors for rotatedBoxToCell!

You can use the #calc macro that we already used in the very first lecture to do the rotation. The setFieldsDict should contain line like this:

// define variables
// origin of rotated box
X0 750;
Y0 -2800;
Z0 0;

width  100; //width of fault zone
height 800; // distance to surface of box
angle 60;  // degrees, counter-clockwise angle between x-axis and fault

// Example using #calc macro
angleRadians  #calc "degToRad($angle)";  // Convert angle to radians

// input for rotatedBoxToCell
i0 ???;
i1 ???;
i2 ???;

j0 ???;
j1 ???;
j2 ???;

regions
(
    rotatedBoxToCell
    {
        origin   ( ? ? ?);
        i        ( ? ? ?);
        j        ( ? ? ?);
        k        ( ? ? ?);

        fieldValues
        (
            volScalarFieldValue permeability 1e-13
        );
    }
);

Step 3

Explore the results in paraview! And investigate how the results change for different fault widths and permeability contrasts.

Fig. 38 Hydrothermal flow along a preferential pathway.

Tip

• Run many simulations for different fault widths and permeabilities

• Explore how vent temperature changes

• …and when the plume is captured by the fault!