# Creating a Domain with a Pole

We would like to create a circular domain with a singularity at the center. Let us start with a circular connector like one seen below.

Now, we need to create a pole connector at the center.

1. Create, Draw Curves, Pole
2. In Point Placement, enter 0 0 0 for XYZ.
3. OK
4. That created a pole connector at the origin. This pole, just like any other connector, has a fixed number of grid points. However, all these grid points are located at the same point - it is a singularity. The pole connector and the outer circular connector will need to have the same number of grid points in order to create a computationally balanced structured domain.

5. Select both connectors.
6. Enter 41 for Dimension.

7. Next we need a branch connector to create a rectangular topology for the structured domain.

8. Click on the 2 Points Curve icon in the toolbar.
9. Select the pole connector.
10. Select the node of the circular connector.
11. Select the resulting connector.
12. Enter 11 for Dimension.

13. If you select all the connectors and click on Assemble Domains, you will notice that nothing happens. That is because there are only three connectors and Pointwise cannot determine how to assemble them into a structured domain.

To create a structured domain, you need 4 edges in which opposite edges have the same number of grid points. You can think of the circular, branch and pole connectors as edges of a rectangle folded in a circular manner so that the two edges dimensioned to 11 coincide with each other, as can be seen in the figure below.

So, 1 connector needs to be specified twice.

14. Create, Assemble Special, Domain.
15. Make sure Auto Next Edge and Auto Complete are unchecked.
16. Select the pole.
17. Next Edge
18. Select the “branch” connector.
19. Next Edge
20. Select the circular connector.
21. Select the “branch” connector once again.
22. OK.

We now have a structured domain with a pole. The elements originating from the center are quads with a degenerate edge. That is how they will be treated in a structured solver, which supports poles. If the structured solver you plan on using does not support poles, you will need to use a different topology, as explained here: www.pointwise.com/DIY/Removing-a-Pole-from-a-Structured-Domain.shtml

Back to the main DIY training page.