Tutorial 5: Compact Enrichment

This tutorial demonstrates a technique for improving cell densities in specific areas of a grid, called compact enrichment.

We will use the surface defined in the file 'NACA8012.lin'. This is a NACA airfoil, defined by a set of equations, then converted into a linear surface file for the purpose of this tutorial.

Load the airfoil and create a rectangle around it, then split the rectangle using the Split Rectangle button.

First we will demonstrate the standard "Wrap" topology with the airfoil.

Notice that the cell density around the leading and trailing edges is rather low. Increasing the density at these points will not have the desired effect, the extra cells will be pushed away from the edges to even out cell densities across the whole grid.

Delete the corners around the airfoil, then create two ellipses centered on the leading and trailing edges of the airfoil as shown. We will use these to push the normal "Wrap" loop of blocks into the surface in these areas to increase local density.

Create the blocks that are part of the "Wrap" around the surface.

Arrows are used to show the "flow" of these blocks around the surface belw.

Next, create blocks on the outside of the ellipse.

Create the blocks that "push" the loop onto the trailing edge of the airfoil, as shown.

Again, blue arrows are used to illustrate the flow of the wrap blocks, and red arrows show the blocks which compress these blocks around the surface.

Assign these corners to the ellipse as shown.

Assign these corners to the airfoil.

Connect this topology to the outer boundary as shown. You will need to insert corners to complete the connection.

Repeat the process for the leading edge of the airfoil. Create blocks on the surface of the airfoil.

Blocks inside the ellipse:

Blocks outside the ellipse:

Assign corners as shown:

Connect these blocks to the outer boundary.

Complete the connections between the blocks on the leading and trailing edges.

Insert corners, or adjust link density to even out grid density. Inserting corners to create more blocks is shown below. First vertically:

Then horizontally:

Apply boundary layer clustering to the airfoil.

Be sure to set both ellipses to "2-sided" otherwise grid generation will fail.

The final grid is shown below.

Zoomed in on the trailing edge:

Zoomed in on the tip: