To model a problem involving a single rotating reference frame, follow the steps outlined below.
 1.
Select the
Velocity Formulation
to be used in the
Solver panel: either
Relative or
Absolute. (See Section
10.7.1 for details.)
Define
Models
Solver...
(Note that this step is irrelevant if you are using one of the densitybased solvers; these solvers always use an absolute velocity formulation.)
 2.
For each cell zone in the domain, specify the angular velocity
(
) of the reference frame and the axis about which it rotates.
Define
Boundary Conditions...
 (a)
In the
Fluid panel or
Solid panel, specify the
RotationAxis Origin and
RotationAxis Direction to define the axis of rotation.
 (b)
Also in the
Fluid (Figure
10.7.1) or
Solid panel, select
Moving Reference Frame in the
Motion Type dropdown list and then set the
Speed under
Rotational Velocity in the expanded portion of the panel.
Details about these inputs are presented in Section
7.17.1 and in Section
7.18.1.
Figure 10.7.1: The
Fluid Panel with the
Moving Reference Frame Selected



For solid zones, you only need to activate the
Moving Reference Frame option if you intend to include the convective terms in the energy equation for the solid (Equation
13.211). Normally, this is not required if you wish to do a conjugate heat transfer problem where the solid and fluid zones are moving together.

 3.
Define the velocity boundary conditions at walls.
You can choose to
define either an absolute velocity
or a velocity relative
to the moving reference frame (i.e., relative to the velocity of the adjacent cell zone specified in step 2), as shown in Figure
10.6.2.
If the wall is moving at the speed of the rotating frame (and hence stationary in the rotating frame), it is convenient to specify a relative angular velocity of zero. Likewise, a wall that is stationary in the nonrotating frame of reference should be given a velocity of zero in the absolute reference frame. Specifying the wall velocities in this manner obviates the need to modify these inputs later if a change is made in the rotational velocity of the fluid zone.
Details about these inputs are presented in Section
7.13.1.
 4.
Define the velocity at any velocity inlets and the flow direction and total pressure at any pressure inlets. For velocity inlets, you can choose to define either absolute velocities or velocities relative to the motion of the adjacent cell zone (specified in step 2). For pressure
inlets,
the specification of the flow direction and total pressure will be relative or absolute, depending on the velocity formulation you selected in step 1. See Section
10.7.1 for details. (If you use one of the coupled solution algorithms, the specification is always in the absolute frame.)
Details about these inputs are presented in Sections
7.3.1 and
7.4.1.