What Is the Fan Momentum Source?

The fan momentum source employs an "actuator disk" type of methodology. With this methodology, the detailed geometry of the fan blades are not modeled. Rather, momentum sources are input to the cells swept out by the blades.

Since the momentum sources are based on theory, there is no guarantee that the resulting flow rate and pressure rise will lie in the fan curve of a particular fan. However, if a fan performance curve is available, then the momentum sources may be adjusted so that the operating point of the installed fan falls on the fan curve.

Properties

Blade Angle

Sets the value and units of the blade angle with respect to flow. Clicking on the ellipsis button lets you select the units from a drop-down menu and enter the value.

Coordinate System

The coordinate system to use. Types other than laboratory will not be available for selection until you create them.

You can use any of the coordinate system types for fan modeling, provided the z-axis runs along the fan axis and is oriented in the fan-flow direction.

Cartesian

Specifies the Cartesian coordinate system.

Cylindrical

Specifies the cylindrical coordinate system.

Laboratory

Specifies the laboratory coordinate system.

Spherical

Specifies the spherical coordinate system.

Data Rotation Rate

The speed at which the fan performance test was conducted. The fan curve is adjusted by classical fan laws when values for this differ. If you want to use a different operating speed, you would enter it in the Operating Rotation Rate property.

Data Temperature

The temperature at which the fan performance test was conducted. The fan curve is adjusted by classical fan laws when values for this differ. Temperature is taken as the mass flow average of the temperature coming into the fan.

Downstream Boundary

You must select a boundary of the type in-place interface. If none appears in the drop-down list, you need to create an in-place interface.

Operating Rotation Rate

The fan speed for this simulation. If you want to use a value different from the speed at which the fan performance test was conducted, enter it here.

Table

Selects a tabular data set to specifying the fan performance curve.

Table: P

The column for pressure data within the fan performance table file.

Table: VolDot

The column for volumetric flow data within the fan performance table file.

Upstream Boundary

You must select a boundary of the type in-place interface. If none appears in the drop-down list, you need to create an in-place interface.