Tutorial 4: Intersecting Surfaces With a Reflex Angle

This geometry is similar to the previous, only this time, we want to create a grid inside the area bounded by both ellipses.

Create two ellipses as shown below

Create topology around the surfaces as shown.

Create a wrap towards the inside of the topology, as shown.

Link and assign corners as shown to complete the topology.

The grid for this topology is shown below.

You may encounter problems with this type of topology. Two blocks are being bent around a reflex angle at the surface intersection, which may cause highly skewed cells as shown below.

This problem can be solved by creating an internal surface that bisects the angle.

You can create a curve like the one shown below using Tecplot's poly-line tool

There is another issue that you must be mindful of in this situation.

The highlighted corners below have 5 links, which is known as a "singularity". These should not be assigned to a surface.

A row of points should be inserted and assigned to the internal surface as shown.

Surfaces with blocks assigned to both sides must be specified as 2-sided using the Surface Properties button.

Adjust surface assignments to add two points to the upper surface, as shown.

... and subtract two points from the lower surface, as shown.

Here is the resulting grid.

The highly skewed cells at the corner have been fixed.