Add a Journal Bearing to points corresponding to the journal bearing location for modeling the effect of the bearing. You can select multiple points to add identical bearings at several locations.
Use the settings in this section to define the local y direction of the bearing. Subsequent vector and matrix inputs are specified in the local directions specified here.
Enter the Bearing orientation vector defining the local y direction. The direction given will be adjusted so that it is orthogonal to the rotor axis. The default value is the global
y-axis.
You can further modify the y-axis orientation by entering an angle for the
Rotation of the orientation vector around the bearing axis. The direction inferred from the previous setting will be rotated counterclockwise around the rotor axis.
Select a Bearing Model —
No clearance,
Cylindrical hydrodynamic,
Total spring and damping constant, or
Total force and moment. Then, go to the relevant section below to continue defining the section.
Clear the Constrain bending rotation checkbox (selected by default) to allow the bending rotation of the rotor at the bearing location.
Enter the Bulk Viscosity,
μ, of the lubricant;
Clearance,
C, between the journal and bushing; the
Journal radius,
R; and the
Journal length,
L. For the
Bulk viscosity, select
From material to use data from a material assigned to the selected journal boundaries, or select
User defined to enter a value or expression.
Clear the Include torsional stiffness checkbox to ignore the resistance of the bearing to the rotations of the journal.
Enter the translational and bending stiffness, ku and
kθ. Select the
Translational-rotational coupling checkbox to also model the coupling between the translational and rotational motion of the journal. Enter the values of the additional inputs,
kuθ and
kθu in this case. If you want to perform dynamic analysis, you can also enter nonzero translational and bending damping constants
cu and
cθ. Select the
Translational-rotational coupling checkbox and enter the
cuθ and
cθu values to include the translational-rotational coupling in damping constants.
Enter the Total force,
Ftot and
Total moment,
Mtot, as a function of journal displacement and rotation. Default expressions are provided as an example of how to specify the forces and moments as a function of journal displacement and rotation. These expressions contain variables of the type
<phys>.<feat>.{du2, du3, dth2, dth3}, which are the lateral components of the journal displacement and rotation of the journal in the local bearing directions.
If the No axial vibration checkbox in the
Axial and Torsional Vibration section of the interface settings is not selected, the
Constrain axial motion checkbox will be visible. Clear this checkbox if you want to use the
Thrust Bearing node to restrict the axial motion.
Select one of the Fixed,
Moving,
Flexible, or
Squeeze-film damper foundation options. If the model component also contains other structural physics interfaces such as
Solid Mechanics,
Multibody Dynamics, and
Shell that have
Attachment or
Rigid Domain features, the above list is extended with the list of the attachments and rigid domains available in these physics interfaces. In the
Moving,
Flexible, and
Squeeze-film damper cases, the subnodes
Moving Foundation,
Flexible Foundation, or
Squeeze-Film Damper are automatically added. If any of the attachments or rigid domains is selected, displacement and rotation of the selected feature are used as foundation motion. Attachments and rigid domains provide an easy way of coupling the rotor with the stator.