### 17.4.1. Single-Phase Fluid Sources

In a single-phase simulation, the volumetric or total source terms are set on the Sources tab. For details, see Sources in the CFX-Solver Modeling Guide.

1. Select the Sources check box to specify sources for the subdomain.

2. Select the Momentum Source/Porous Loss check box to specify a momentum source.

   For details, see Momentum Source/Porous Loss.

3. Select the equation source to specify.

   Equation sources include other sources such as mass fraction, energy, continuity (mass), turbulence, Additional Variables, and so on. For details, see:

   - Equation Sources

   - Source Coefficient / Total Source Coefficient in the CFX-Solver Modeling Guide.

#### 17.4.1.1. Momentum Source/Porous Loss

A source of momentum is introduced by setting X, Y and Z, or r, Theta and Axial components for the momentum source under General Momentum Source. All three components must be set if a general momentum source is defined. You can optionally specify a Momentum Source Coefficient to aid convergence. When employing a cylindrical coordinate frame, you must specify an axis using a rotation axis or two points.

In addition to specifying a general source of momentum, you can model porous loss in a flow using an isotropic or directional loss model. In each case, the loss is specified using either linear and quadratic coefficients, or permeability and loss coefficients. For the Directional Loss model, the loss in the transverse direction can be set using the `Loss Coefficient`, which multiplies the streamwise loss by the entered factor. When using the Directional Loss model, you must supply a streamwise direction. The direction can be specified with Cartesian or cylindrical coordinates. If you choose cylindrical coordinates, specify the axis using a rotation axis or two points.

For additional details on modeling momentum sources, see Momentum Sources in the CFX-Solver Modeling Guide.

#### 17.4.1.2. Equation Sources

Equation Sources introduces source terms to a particular scalar equation.

##### 17.4.1.2.1. Component Mass Fractions

This will introduce a source of a particular component. A `Source` per unit volume or a `Total Source` can be used. The optional Source Coefficient or Total Source Coefficient provides improved convergence for nonlinear sources. For details, see General Sources in the CFX-Solver Modeling Guide.

1. In the Option and Source fields, set a component source term for a mixture.

   This can be an expression or value for the total source or the source per unit volume. For details, see General Sources in the CFX-Solver Modeling Guide.

2. Set an optional Total Source / Source Coefficient.

   For details, see Source Coefficient / Total Source Coefficient in the CFX-Solver Modeling Guide.

##### 17.4.1.2.2. Additional Variables

A source for an Additional Variable can be set only if it is included in the parent domain and solved for using a transport equation. (Poisson and Diffusive transports can also have sources.) A `Source` per unit volume or a `Total Source` can be used. The optional Source Coefficient or Total Source Coefficient provides improved convergence for nonlinear sources. For details, see General Sources in the CFX-Solver Modeling Guide.

1. In the Option and Source fields, set an Additional Variable Source term.

   For details, see General Sources in the CFX-Solver Modeling Guide.

2. Set an optional Total Source / Source Coefficient.

   For details, see Source Coefficient / Total Source Coefficient in the CFX-Solver Modeling Guide.

##### 17.4.1.2.3. Continuity

`Continuity` sources differ from other sources because you are introducing new fluid into the domain. Properties of the fluid entering the domain are required and appear in the Variables frame under the Continuity section. For details on the following settings, see Mass (Continuity) Sources in the CFX-Solver Modeling Guide.

- Continuity > Source: Set a mass source value for the continuity equation.

- Continuity > Option: Set the `Fluid Mass Source` per unit volume or the `Total Fluid Mass Source`.

- MCF/Energy Sink Option: Select the appropriate sink option from `Local Mass Fractions and Temperature`, `Specified Mass Fractions and Local Temperature`, or `Specified Mass Fractions and Temperature`, as appropriate.

- Set a value for the Mass Flux Pressure Coefficient, Total Mass Source Pressure Coefficient or Mass Source Pressure Coefficient, as appropriate.

- Set a value for the Mass Flux Volume Fraction Coefficient, Total Mass Source Volume Fraction Coefficient or Mass Source Volume Fraction Coefficient, as appropriate.

- Set the variable values for the fluid that is introduced into the domain. The options available on this section depend on the physical models used in the simulation. If the continuity source is negative, then these parameters are not relevant except in the case when either `Specified Mass Fractions and Local Temperature`, or `Specified Mass Fractions and Temperature` have been selected for the MCF/Energy Sink Option.

  - Additional Variables: Set a value for each Additional Variables that is introduced with the mass source.

  - Component Mass Fractions: Set the mass fraction for each of the components in the mass source.

  - Temperature: Enter the temperature for the mass source.

  - Set the mass source turbulence quantities as required by the selected turbulence model such as Turbulence Eddy Dissipation and Turbulence Kinetic Energy.

  - Velocity: Set velocity components for the mass source.

##### 17.4.1.2.4. Turbulence Quantities

When the flow is turbulent, sources can be specified for the required turbulence quantities such as `Turbulence Eddy Dissipation` and `Turbulence Kinetic Energy`. A `Source` per unit volume or a `Total Source` can be used. The optional Source Coefficient or Total Source Coefficient provides improved convergence for nonlinear sources. For details, see General Sources in the CFX-Solver Modeling Guide.

##### 17.4.1.2.5. Energy

An `Energy` source can be specified when the parent domain models heat transfer using the Thermal Energy or Total Energy model. A `Source` per unit volume or a `Total Source` can be used. The optional Source Coefficient or Total Source Coefficient provides improved convergence for nonlinear sources. For details, see General Sources in the CFX-Solver Modeling Guide.

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