Consider an example case of an XK-8050 particle gun. The global element size of the initial mesh is 1 mm. We would like to control the mesh locally around the centerline of the gun where the particles flow.
The gold-colored solid below is the sub-volume of interest (we could have used a 360-degree sub-volume). Note that the initial dimensions of the sub-volume are arbitrary, it just needs to extend to or beyond the model.
Assume that the starting structure already has boundary conditions applied, and that we want an element size of 0.2 mm in the region of interest. To proceed:
On the Structure ribbon in the Entity Modification group, click the Boolean button and select Region.
Click the gun, then press Enter or click Done to select the stock for the region.
Click the sub-volume, then press Enter or click Done to select the tool for the region. A node for the region appears in the Browser. The Region operation results in a single solid with 2 bodies.
On the Structure ribbon in the Attributes group, click the New Attribute menu and select Mesh Constraint. Double-click the Region to select it, then press Enter or click Done.
In the properties dialog box that displays, set the Element Size > Type to Local Absolute and set the Absolute Size to 0.02 cm. Click OK or press Enter to close the dialog box.
The mesh, with the local mesh constraint added, will look like this:
While this method is appropriate for simple cases, it has the following drawbacks:
Because the topology has changed, existing attribute applications may be altered and/or removed.. This can be painful unless anticipated early in the model development.
Additional faces and edges are added to the model, which can complicate picking and overall topology.