Many product designs involve an assembly of components in order to create the final product. In the geometry sequence of a COMSOL Multiphysics® model, these components correspond to geometric objects. When building a model, it is important how we treat, or finalize, a collection of objects before meshing and defining the physics. In this video, we show you the differences in and implications of finalizing your geometry with Form Union versus Form Assembly.
The Form Union and Form Assembly methods both unite the geometric objects into a single object. When using Form Union, the software generates a composite object that consists of connected domains separated by shared boundaries between the neighboring entities. When using Form Assembly, the software instead groups the objects into a single object that contains a collection of disconnected domains. While the default Form Union method results in a connected mesh across the domains, the mesh after Form Assembly is disconnected. In that case, continuity for the physics across the domains is assured via the automatic generation of identity pairs for the touching boundaries. Form Assembly is especially useful when objects need to be able to move in a simulation.