The Fan condition is used to define the flow direction (inlet or outlet) and the fan parameters on exterior boundaries. The Interior Fan condition is available on interior boundaries.

The Flow direction can be set to Inlet or Outlet. When a boundary has been selected, an arrow displays in the Graphics window to indicate the selected flow direction. The arrow can be updated if the selection changes by clicking any node in the Model Builder and then clicking the Fan node again to update the Graphics window.

The Inlet Flow direction controls in which direction the fluid enters the domain.

When Inlet is selected as the Flow direction, the Input pressure pinput defines the pressure at the fan inlet.

When Outlet is selected as the Flow direction, the Exit pressure pexit defines the pressure at the fan outlet.

When Include gravity is selected and Use reduced pressure is not selected in the interface’s Physical model section, the Compensate for hydrostatic pressure (named Compensate for hydrostatic pressure approximation for weakly compressible or compressible flow) check box is available and selected by default. When it is selected, the hydrostatic pressure is automatically added to the pressure entered in pinput or pexit user input.

For either flow direction, Static pressure curve specifies a fan curve — Linear, Static pressure curve data, or User defined.

For both Inlet and Outlet flow directions, if Linear is selected, values or expressions for the Static pressure at no flow pnf and the Free delivery flow rate V0,fd should be specified. The static pressure curve is equal to the static pressure at no flow rate when V0 < 0 and equal to 0 when the flow rate is larger than the free delivery flow rate.

With the User defined option, a different value or expression for the Static pressure curve can be specified. The flow rate across the selection where this boundary condition is applied is defined by phys_id.V0 where phys_id is the name (for example, phys_id is spf by default for laminar single-phase flow). In order to avoid unexpected behavior, the function used for the fan curve returns the maximum of the user-defined function and 0.

The Static pressure curve data can be entered or loaded under the Static Pressure Curve Data section that displays for this option. The interpolation between points given in the table is defined using the Interpolation function type list in the Static Pressure Curve Interpolation section.

This section is available when Static pressure curve data is selected as the Static pressure curve. Units can be specified for the Flow rate and Static pressure.

When Static pressure curve data is selected as the Static pressure curve, a table appears, where values or expressions the Flow rate and Static pressure can be specified or imported from a text file by clicking the Load from file button () under the table. Units can be specified for the Flow rate and the Static pressure curve.

This section is available when Static pressure curve data is selected as the Static pressure curve. The available options for the Interpolation function type are Linear, Piecewise cubic, and Cubic spline.

When Inlet is selected as the Flow direction and the Turbulence model has transport equations for the turbulent kinetic energy, k, and turbulent dissipation rate, ε, specific dissipation rate, ω, or turbulent relative fluctuations, ζ, the values of the Turbulent kinetic energy, Turbulent relative fluctuations (for the v2-f turbulence model) and the Turbulent dissipation rate or Specific dissipation rate on the downstream side of the fan should be specified. Alternatively, the Reference velocity scale can be used to specify default values.