More Mesh Refinements

by Nate Hekman on October 23, 2013

In Meshing Efficiently, I touched briefly on different ways of refining your mesh.  After a question from a reader today I thought it would be worthwhile visiting this topic again.

Start by choosing Draw – Mesh Properties from the menu.  Set the global–or default–mesh size.  Then add constraints to specific pieces of the geometry to tweak the mesh size where necessary.

Global Element Size

Adjust the “default” mesh size across the entire domain by setting the Global Element Size.  We call this the approximate size because it’s just a guide to the meshing algorithm.

meshing-global

Constrain a Region

Click on a region to add a constraint to that region.  For example, here I’ve requested that the lower region have 0.5m element edges instead of the global 2m.  You can see that the lower region has uniform elements, whereas the top region starts out with 0.5m elements (we can’t have discontinuity between the two) but heads toward 2m elements the further away it is from the constraint.

meshing-region

Here’s a tip:  if your region is very small, it may be difficult to select it in order to add a constraint–you’ll end up selecting its lines or points instead.  Here I’m trying to select the region but only get the “line” cursor:

meshing-zoomed

The solution is to zoom in.  The larger (visually) the region, the more “region” space you can click on.

meshing-zoomed

Constrain a Line

Click on a line to add a constraint to that line.  This time elements along the line have 0.5m edges but get larger as they move away from the line.  The mesh in the upper region is unaffected.

meshing-line

If I put the constraint on the horizontal line instead, both regions’ meshes are affected since they both share that line.

meshing-shared-line

Constrain a Point

Click on a point to give it a constraint.  The mesh is dense by that point but gets coarser the further away it gets.

meshing-point

 

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