For any given CFD problem, more than one domain may be defined. By default, the physical models used in each domain must be consistent; therefore, each time you create or edit a domain, the physical models (fluid lists, heat transfer models, and so on) are applied across all domains of the same type (such as fluid or solid), possibly overwriting models chosen earlier for other domains.
Note the following:
Some exceptions exist when using fluid and solid domains together and also to enable MFR (multiple frame of reference) simulations to be defined.
If a domain interface is required, refer to Using Domain Interfaces in the CFX-Solver Modeling Guide for information on the correct use of interfaces.