cmomega#

Inertia.cmomega(cm_name='', omegax='', omegay='', omegaz='', x1='', y1='', z1='', x2='', y2='', z2='', **kwargs)#

Specifies the rotational velocity of an element component about a user-defined rotational axis.

Mechanical APDL Command: CMOMEGA

Parameters:
cm_namestr

The name of the element component.

omegaxstr

If the X2, Y2, Z2 fields are not defined, OMEGAX, OMEGAY, and OMEGAZ specify the components of the rotational velocity vector in the global Cartesian X, Y, Z directions.

If the X2, Y2, Z2 fields are defined, only OMEGAX is required. OMEGAX specifies the scalar rotational velocity about the rotational axis. The rotational direction of OMEGAX is designated either positive or negative, and is determined by the “right hand rule.”

omegaystr

If the X2, Y2, Z2 fields are not defined, OMEGAX, OMEGAY, and OMEGAZ specify the components of the rotational velocity vector in the global Cartesian X, Y, Z directions.

If the X2, Y2, Z2 fields are defined, only OMEGAX is required. OMEGAX specifies the scalar rotational velocity about the rotational axis. The rotational direction of OMEGAX is designated either positive or negative, and is determined by the “right hand rule.”

omegazstr

If the X2, Y2, Z2 fields are not defined, OMEGAX, OMEGAY, and OMEGAZ specify the components of the rotational velocity vector in the global Cartesian X, Y, Z directions.

If the X2, Y2, Z2 fields are defined, only OMEGAX is required. OMEGAX specifies the scalar rotational velocity about the rotational axis. The rotational direction of OMEGAX is designated either positive or negative, and is determined by the “right hand rule.”

x1str

If the X2, Y2, Z2 fields are defined, X1, Y1, and Z1 define the coordinates of the beginning point of the rotational axis vector. Otherwise, X1, Y1, and Z1 are the coordinates of a point through which the rotational axis passes.

y1str

If the X2, Y2, Z2 fields are defined, X1, Y1, and Z1 define the coordinates of the beginning point of the rotational axis vector. Otherwise, X1, Y1, and Z1 are the coordinates of a point through which the rotational axis passes.

z1str

If the X2, Y2, Z2 fields are defined, X1, Y1, and Z1 define the coordinates of the beginning point of the rotational axis vector. Otherwise, X1, Y1, and Z1 are the coordinates of a point through which the rotational axis passes.

x2str

The coordinates of the end point of the rotational axis vector.

y2str

The coordinates of the end point of the rotational axis vector.

z2str

The coordinates of the end point of the rotational axis vector.

Notes

Specifies the rotational velocity components OMEGAX, OMEGAY, and OMEGAZ of an element component CM_NAME about a user-defined rotational axis. The rotational axis can be defined either as a vector passing through a single point or a vector connecting two points.

You can define the rotational velocity and rotational axis for these analysis types:

  • Static ( antype,STATIC)

  • Harmonic ( antype,HARMIC) – full, VT [ CMOMEGA_FN_VT_KRY ], Krylov [ CMOMEGA_FN_VT_KRY ], or mode-superposition [ CMOMEGA_mode-sup_LVSCALE ]

  • Transient ( antype,TRANS) – full or mode-superposition [ CMOMEGA_mode-sup_LVSCALE ]

  • Substructuring ( antype,SUBSTR)

  • Modal ( antype,MODAL)

Loads for VT and Krylov methods are supported as long as they are not:

  • complex tabulated loads (constant or trapezoidal loads in tabulated form are supported)

  • used in conjunction with Rotordynamics ( coriolis,on).

In a mode-superposition harmonic or transient analysis, you must apply the load in the modal portion of the analysis. Mechanical APDL calculates a load vector and writes it to the MODE file, which you can apply via the lvscale command.

Rotational velocities are combined with the element mass matrices to form a body-force load vector term. Units are radians/time. Related commands are acel, cgloc, cgloc, cgomga, cmdomega, dcgomg, domega.

See Analysis Tools

You can use the cmomega command in conjunction with either one of the following two groups of commands, but not with both groups simultaneously:

  • GROUP ONE: omega, domega.

  • GROUP TWO: cgomga, dcgomg, cgloc.

Components for which you want to specify rotational loading must consist of elements only. The elements you use cannot be part of more than one component, and elements that share nodes cannot exist in different element components. You cannot apply the loading to an assembly of element components.

If you have applied the Coriolis effect ( coriolis ) using a stationary reference frame, the cmomega command takes the gyroscopic damping matrix into account for the elements listed under “Stationary Reference Frame” in the notes section of the coriolis command. Mechanical APDL verifies that the rotation vector axis is parallel to the axis of the element; if not, the gyroscopic effect is not applied. If you issue a cmomega command when the Coriolis or gyroscopic effect is present, a subsequently issued omega command has no effect.

The cmomega command supports tabular boundary conditions (TABNAME_X, TABNAME_Y, and TABNAME_Z) for OMEGAX, OMEGAY, and OMEGAZ input values ( dim ) for modal, full transient, and full harmonic analyses. In this case, if the end point is specified ( X2, Y2, Z2 ), the rotational velocity axis must be along the global X-, Y-, or Z-axis.

The load interpolation setting ( kbc ) applies to the rotational velocity, in particular the OMGSQRDKEY option for quadratic interpolation.