The following methods are available for reporting velocities:
For all of the above definitions of the cylindrical coordinate system, positive radial velocities point radially out from the rotation axis, positive axial velocities are in the direction of the rotation axis vector, and positive tangential velocities are based on the right-hand rule using the positive rotation axis.
To report cylindrical velocities, select Axial Velocity, Radial Velocity, etc. Figure 30.2.1 illustrates the cylindrical velocities available for different types of domains: For 3D problems, you can report axial, radial, and tangential velocities. For 2D problems, radial and tangential velocities are available. For axisymmetric problems, you can report axial and radial velocities, and if you are modeling axisymmetric swirl you can also report the swirl velocity (which is equivalent to the tangential velocity).
If you are using a single rotating reference frame, the relative velocity values will be reported with respect to the moving frame. If you are using multiple reference frames, mixing planes, or sliding meshes, you will need to specify the frame to which you want the velocities to be relative by choosing the appropriate cell zone as the Reference Zone in the Reference Values panel (see Section 29.10). The axis of rotation for each cell zone is defined in the associated Fluid panel or Solid panel. (See Section 7.17.1 or 7.18.1 for details.)
Note that if your problem does not involve any moving zones, relative and absolute velocities will be equivalent.
Note that relative velocities can also be used to compute stagnation quantities (total pressure and total temperature), and that the cylindrical coordinate systems described in the second item above are used for defining the Axial Coordinate and Radial Coordinate as well.