LaGriT/docs/pages/tutorial/stratigraphy/step_04.md

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4. Map Surfaces to Mesh

Now that the straitipgrahy has been modeled and we are comfortable with our results, we will map their spanning domain to the parent mesh. As done with the psets above, this process will be driven via attributes.

We now have two planes spanning the X,Y domain of the mesh. These planes can be leveraged to create different material IDs at different regions of the subsurface.

For example,

• For all nodes/cells above plane 1, set their material ID to 1
• For all nodes/cells between plane 1 and plane 2, set their material ID to 2
• For all nodes/cells below plane 2, set their material ID to 3

This process can be accomplished by:

1. Defining the above regions using the region keyword
2. Capturing the relevant nodes and elements that fall within the defined regions
3. Setting the node and element material IDs based on the psets and eltsets

4.1 Defining Regions

The syntax for region is:

 region / region_name / region_definition

where region_definition is a string composed of boolean operators and instantiated surface objects.

Recall that we have defined two planes, mosurf1 and mosurf2. We would like to generate the region objects from these planes, but the arguments for region require surface objects.

Fortunately, we can map the planes to a surface very easily. The syntax for generating a surface object from a quad or triangle mesh is:

 surface / surface_name / reflect / sheet / input_mesh

The two planes can then be mapped to surface objects:

surface / s_1 / reflect / sheet / mosurf1
surface / s_2 / reflect / sheet / mosurf2

And finally, we can remove the plane meshes and define regions:

cmo / delete / mosurf1
cmo / delete / mosurf2
cmo / select / MONAME

region / r_1 / le s_1
region / r_2 / gt s_1 and le s_2
region / r_3 / gt s_2

4.2 Creating Eltsets and PSets from Regions

Point sets and element sets can easily be created through region objects. The syntax is:

 pset / pset_name / region / region_object / 1,0,0
 eltset / eltset_name / region / region_object

Applying this to our region objects yields:

pset   / p_r_1 / region / r_1 / 1 0 0
pset   / p_r_2 / region / r_2 / 1 0 0
pset   / p_r_3 / region / r_3 / 1 0 0

eltset / e_r_1 / region / r_1
eltset / e_r_2 / region / r_2
eltset / e_r_3 / region / r_3

4.3 Setting Attributes from Eltsets and PSets

Recall that the node attribute imt holds the 'node colors' of the mesh, and cell attribute itetclr stores the 'cell colors' (or material ID).

Let's use the defined psets and eltsets to change these:

cmo / setatt / MONAME / imt     / pset   get p_r_1 / 1
cmo / setatt / MONAME / imt     / pset   get p_r_2 / 2
cmo / setatt / MONAME / imt     / pset   get p_r_3 / 3

cmo / setatt / MONAME / itetclr / eltset get e_r_1 / 1
cmo / setatt / MONAME / itetclr / eltset get e_r_2 / 2
cmo / setatt / MONAME / itetclr / eltset get e_r_3 / 3

Our mesh's cells and nodes now store information about their intersections with the cut-planes. Visualizing itetclr, we can see that this has behaved as expected:

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• Index
• 1. Building a Hex Mesh
• 2. Define Boundaries Using Point Sets
• 3. Constructing Stratigraphy
• 4. Map Surfaces to Mesh
• 5. Constructing a Fault
• 6. Truncate with Polyline
• 7. Refine Fault
• 8. Insert Wells
• 9. Convert Hex Mesh to Tet
• 10.1 Write FEHM Files
• 10.2 Write ExodusII Files
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