Merge Meshes
The Merge Meshes option allows you to merge disconnected parts of the mesh if two or more domains are loaded and the nodes do not match up at the interface between them. These domains are usually created separately. The merging will match up the nodes so that one-to-one connectivity is maintained throughout the entire merged domain. Tri elements at the interface of one domain should be no larger than roughly 3 times the tri element size of the other domain. The larger elements will be subdivided at the interface until they reach the size of the elements of the other domain. Tetra/tetra and tetra/hexa merges can also be done. If a tetra mesh and hexa mesh are to be merged, pyramids will be created at the interface.
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Note:
The Merge Meshes option only works well when the quad elements at the interface are close to equilateral