Block Format Keyword Describes the nodal random noise to check stability of model by introducing random noise on nodal coordinates.


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/RANDOM/unit_ID or
Xalea Seed            


Field Contents SI Unit Example
grnd_ID Node group identifier (defined only if the keyword GRNOD is set).


unit_ID Unit Identifier.

(Integer, maximum 10 digits)

Xalea Maximum nodal random noise.

Range: [0, + ∞] (Real)

[ m ]
Seed Seed of random noise.

Range: [0, 1] (Real)



  1. Xalea is the maximum magnitude of generic random noise applied to specified nodes coordinates (any direction). The modified coordinate = original one + Xalea * random number defined by Radioss (random number is defined between 0 and 1).
  2. Seed is a Real corresponding to the value used to initialize random number generation that should be set between 0 and 1 (1 excluded) for sensitivity analysis or model robustness investigation purpose.
  3. If the Ipri flag defined in /IOFLAG option has a value greater than or equal to 4, the output log file will contain a listing of new node coordinates.
  4. Two computations with the same values for Xalea and Seed will lead exactly to the same results.
  5. If a plain /RANDOM option is used (without GRNOD keyword), the random noise is applied to all nodes. When present, it should be defined only once and be the only random noise option.
  6. The /RANDOM/GRNOD definition is optional and allows to specify a node group affected by random noise. Multiple random noise groups may be defined; however, if one or more /RANDOM/GRNOD blocks are present, the random noise is applied only to the specified node groups, regardless if a plain /RANDOM option is present or not.
  7. Several definitions with groups containing common nodes are allowed, but the randomization of coordinates will be applied more than once for these nodes.
  8. For more information on how to define random noise with a command, refer to Starter Command Line Arguments.