Mesh 1
Set up the mesh. By default, COMSOL Multiphysics will create a mesh for the physics currently in the model. Often this is good enough, but in this case, we want to make some small edits to the default mesh sequence. By default, the fine mesh is not applied to interior boundaries. Typically this is wanted, since interior boundaries are transparent to the fluid flow. However, in this case, the mixing of the two streams occurs close to this interior boundary, so we can add boundary 16, in the middle of the channel, to the Size 1 selection and also to the Boundary Layer Properties 1 mesh feature.
Size
1
In the Model Builder window, under Component 1 click Mesh 1 .
2
In the Settings window for Mesh, locate the Physics-Controlled Mesh section.
3
From the Element Size list, choose Coarse.
4
Right-click Mesh 1 and choose Edit Physics–Induced Sequence.
Size 2
1
In the Model Builder window, under Component 1 (comp1) > Mesh 1 click Size 2.
2
In the Settings window for Size, locate the Geometric Entity Selection section.
3
Click Paste Selection .
4
In the Paste Selection dialog, type 16 in the Selection text field.
5
Click OK.
Boundary Layer Properties 1
1
In the Model Builder window, expand the Component 1 (comp1) > Mesh 1 > Boundary Layers 1 node, then click Boundary Layer Properties 1 .
2
In the Settings window for Boundary Layer Properties, locate the Boundary Selection section.
3
Click Paste Selection .
4
In the Paste Selection dialog, type 16 in the Selection text field.
5
Click OK.
6
Right-click Component 1 (comp1) > Mesh 1 > Boundary Layers 1 > Boundary Layer Properties 1 and choose Build All .