### 1.3.1. Locators for Sources

#### 1.3.1.1. Subdomains

Subdomains are regions of space in a domain in which volumetric sources of mass, momentum, energy, turbulence, Additional Variables, mass fractions and radiation can be specified. They can also be used to model flow resistance. Many subdomains can be created in each domain.

Subdomain regions are defined in the same way as domains, which is from 3D primitives. A 3D primitive used for a subdomain must also be contained in the parent domain. For details, see Mesh Topology in CFX-Pre in the CFX-Pre User's Guide.

Sources on subdomains may be specified as either volumetric quantities (source per unit volume) or as the total source. If a total source is specified, the solver assumes a uniform source density over the subdomain in order to obtain the volumetric quantity.

The total source option is not supported for momentum sources.

#### 1.3.1.2. Boundary Sources

Boundary sources permit the specification of sources as fluxes (source per unit area) on boundary condition surfaces. This applies to all equations, including continuity.

Total sources are also available on boundaries, for which the solver assumes a uniform source density in order to obtain the flux-based quantity.

Momentum sources are not currently available on boundaries.

#### 1.3.1.3. Point Sources

Sources can also be specified at a point. The specified source is distributed among the vertices of the element in which the point is located. The effect of the source will therefore become more pronounced as the mesh is refined.

Momentum sources are not currently available at points.

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