## 1.1. Domains

Regions of fluid flow and/or heat transfer in CFX are called domains. Fluid domains define a region of fluid flow, while solid domains are regions occupied by conducting solids in which volumetric sources of energy can be specified. The domain requires three specifications:

- The region defining the flow or conducting solid. A domain is formed from one or more 3D primitives that constrain the region occupied by the fluid and/or conducting solids. For details, see Mesh Topology in CFX-Pre in the CFX-Pre User's Guide.

- The physical nature of the flow. This determines the modeling of specific features such as heat transfer or buoyancy.

- The properties of the materials in the region.

There can be many domains per model, with each domain defined by separate 3D primitives. Multidomain problems may be created from a single mesh if it contains multiple 3D primitives or is from multiple meshes. For details, see Importing and Transforming Meshes in the CFX-Pre User's Guide.

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