Modeling fan swirl

The Swirl option in the Flow Direction group in the Flow Boundary Condition dialog box lets you model swirl in the fluid introduced by devices, such as a fan or propeller. When the flow through the fan is defined in terms of velocity, volumetric flow rate is preserved.

If you choose Velocity from the Mode list in the Flow Boundary Condition dialog box, the software preserves the volumetric flow rate. The value specified is always the value of the velocity component normal to the fan surface.

Defining the rotation axis

If you choose to include the effects of fan swirl in your analysis, you must specify the Rotation Axis. The Rotation Axis defines the direction of device rotation (and swirl) based on the right hand rule.

Note:

The Rotation Axis vector has no bearing on the flow direction.

The Fixed Angle and Radially Varying options let you specify whether the fluid rotates at a fixed or varying angle.

• To define a Fixed Angle swirl, specify the Normal to Resultant Velocity Angle which is the angle from the device normal to the resultant fluid velocity vector. The rotation of the device deflects the fluid from the device normal, towards the tangential velocity vector as shown in the figure below.Rotation AxisTangential velocity vectorDevice normal Normal to Resultant Velocity AngleResultant fluid velocity vector

• To define a Radially Varying swirl, specify the Rotation Velocity of the fluid at the device. The solver factors this rotational velocity into the calculated or specified Velocity of the fluid at the device.

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Modeling fan swirl, Simcenter 3D 2021.1 Series

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