In the CAD geometry, identify the axisymmetric and non-axisymmetric parts. A non axisymmetric part should be considered as follow:
If inertia is negligible, create a non-rotating component based on this part. The gyroscopic effect will not be taken into account.
If inertia is not negligible, delete the part and create an equivalent axisymmetric geometry so that its gyroscopic effects are included. The simplest way to do this is to add a point mass on the rotational velocity axis. The point mass characteristics are based on the part mass and inertias. The two rotary inertias perpendicular to the rotational velocity axis must be equal to guarantee the axisymmetry.
For 3D and 2D axisymmetric modeling, the geometry is sliced at rigid disks and bearing locations so that those components are easily created and connected to remote points attached to the interfaces.
When meshing a 2D axisymmetric model using SOLID272 or SOLID273, choose an appropriate number of Fourier nodes in the circumferential direction to ensure good accuracy and minimize the computational cost. For typical rotordynamics problems in linear dynamics, three Fourier nodes are sufficient.
When performing a Campbell diagram of a structure, always check the eigenfrequencies at zero rotational velocity first. If the supports (bearings or boundary conditions) are symmetric, bending frequencies should appear in pairs. If that is not the case in a 3D model, try refining the mesh.
To perform the unbalance response analysis of 3D and 2D axisymmetric models, the unbalance response is introduced using complex forces defined at a node on the rotational velocity axis. The unbalance response may be defined using a point mass away from the rotational velocity axis only in the case of a nonlinear transient analysis.