**PRORB****Prints the orbital motion characteristics of a rotating
structure**

Compatible Products: – | – | Premium | Enterprise | Ent PP | Ent Solver | –

When a structure is rotating and the Coriolis or gyroscopic
effect is taken into account (**CORIOLIS**), nodes
lying on the rotation axis generally exhibit an elliptical orbital
motion. The **PRORB** command prints out the orbit
characteristics A, B, PSI, PHI, YMAX and ZMAX of each rotating node,
where

A is the semi-major axis. |

B is the semi-minor axis. |

PSI is the angle between local y axis and major axis. |

PHI is the angle between initial position (t = 0) and major axis. |

YMAX is the maximum displacement along local y axis. |

ZMAX is the maximum displacement along local z axis. |

Angles PSI and PHI are in degrees and within the range of -180
through +180. For more information about orbit definition, see Orbits in the *Advanced Analysis Guide*.

To *display* the characteristics
of the orbital path traversed by each node, issue the **PLORB** command.

The **PRORB** command
is valid for line elements (such as BEAM188, BEAM189, PIPE288, and PIPE289).

Your model must also involve a rotational velocity (**OMEGA** or **CMOMEGA**) with Coriolis enabled
in a *stationary* reference frame
(**CORIOLIS**,,,,* RefFrame* = ON).

A **SET** command should be issued after **PRORB** to ensure proper output for subsequent postprocessing
commands.

The coordinate system for displaying nodal results must be global
Cartesian (**RSYS**,* KCN* =
0).