Add a Thrust Bearing node to model a cross section where a thrust bearing is acting. The selected boundaries should form a circular surface representing the cross section of the rotor.
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 x 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 x-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,
Total spring and damping constant,
Total force and moment, or
Force per reference area. Then go to the relevant section below to continue defining the properties.
Enter the axial and bending stiffness, ku and
kθ. Select the
Translational-rotational coupling checkbox to also model the coupling between the axial and rotational motion of the collar. Enter expressions for the additional inputs,
kuθ and
kθu in this case. If you want to perform dynamic analysis, you can also provide nonzero axial and bending damping constants
cu and
cθ. Select the
Translational-rotational coupling checkbox and enter
cuθ and
cθu values to include the translational-rotational coupling in the damping constants. Default values for the rotational stiffness and damping constants are provided as functions of the axial stiffness. It is assumed that the axial stiffness and damping constants are uniformly distributed on the given selection. The equivalent moment experienced at the center of the collar due to this distribution is considered as the moment from the bearing. The variables
<phys>.<feat>.E{11,22,12,21} and
<phys>.<feat>.area appearing in the default expression are the components of the Euler tensor and area of the collar, respectively. Component indices in the variable E represent the respective components of the Euler tensor in the local bearing directions.
Enter the Total force,
Ftot, and
Total moment,
Mtot, as functions of collar displacement and rotation. To help specifying the force and moment as functions of collar displacement and rotation, default expressions are provided for these inputs. These expressions contain variables of the type
<phys>.<feat>.{du3c,dth1,dth2}, which are relative axial displacement and lateral components of the relative rotation of the collar with respect to the bearing at the center, in the local bearing directions.
Enter the axial force per reference area, FA, in the matrix. This option is useful if the distributed force on the collar surface is known. To help specifying the input as a function of collar axial displacement a default expression is provided. This expression contains the variable
<phys>.<feat>.du3, which is the axial component of the relative surface displacement of the collar with respect to the bearing.
Select the Constrain lateral motion checkbox (cleared by default) if you do not want to use a separate
Journal Bearing node to restrict the lateral motion.
Select one of the Fixed,
Moving, or
Flexible foundation options. If the model component also contains other structural physics interfaces such as
Solid Mechanics,
Multibody Dynamics, or
Shell that have
Attachment or
Rigid Domain features, the above list is extended with the attachments and rigid domains available in these physics interfaces. In the
Moving and
Flexible cases, the subnodes
Moving Foundation or
Flexible Foundation 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.