cmdomega#

Inertia.cmdomega(cm_name='', domegax='', domegay='', domegaz='', x1='', y1='', z1='', x2='', y2='', z2='', **kwargs)#

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

Mechanical APDL Command: CMDOMEGA

Parameters:
cm_namestr

The name of the element component.

domegaxstr

If the X2, Y2, Z2 fields are not defined, DOMEGAX, DOMEGAY, and DOMEGAZ specify the components of the rotational acceleration vector in the global Cartesian X, Y, Z directions.

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

domegaystr

If the X2, Y2, Z2 fields are not defined, DOMEGAX, DOMEGAY, and DOMEGAZ specify the components of the rotational acceleration vector in the global Cartesian X, Y, Z directions.

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

domegazstr

If the X2, Y2, Z2 fields are not defined, DOMEGAX, DOMEGAY, and DOMEGAZ specify the components of the rotational acceleration vector in the global Cartesian X, Y, Z directions.

If the X2, Y2, Z2 fields are defined, only DOMEGAX is required. DOMEGAX specifies the scalar rotational acceleration about the rotational axis. The rotational direction of DOMEGAX 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 acceleration components DOMEGAX, DOMEGAY, and DOMEGAZ 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 acceleration and rotational axis with the cmdomega command for these analyses:

  • Static ( antype,STATIC)

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

  • Transient ( antype,TRANS) – full or mode-superposition [ CMDOMEGA_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 2.

The cmdomega command supports tabular boundary conditions (TABNAME_X, TABNAME_Y, and TABNAME_Z) for DOMEGAX, DOMEGAY, and DOMEGAZ input values ( dim ) for full transient and 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.

Related commands are acel, cgloc, cgloc, omega, cmomega, dcgomg, domega.

See Analysis Tools

You can use the cmdomega command in conjunction with any 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.

See Acceleration Effect

This command is also valid in PREP7.