A Random Vibration node () defines a random vibration analysis based on a frequency response model, primarily for structural mechanics simulations. This feature makes it possible to postprocess the probability spectral density (PSD) of a Frequency Domain, Modal Reduced-Order Model’s response to random loads described by their power spectra. The output is presented using operators like <rom_name>.psd(...), <rom_name>.rms(...), and <rom_name>.cross(...) where <rom_name> is the Name of the Random Vibration node. For details, see Performing a Random Vibration Analysis in the Structural Mechanics Module User’s Guide.

The Settings window for a Random Vibration node contains the following sections:

From the Frequency response model list, choose an existing Frequency Domain, Modal Reduced-Order Model node representing the frequency-domain behavior of the structure.

From the Correlation type list, choose a type of correlation: Uncorrelated (the default), Fully correlated, or Cross-correlated. If you choose Cross-correlated, a correlation matrix appears at the bottom of this section.

For each reduced-order model input used in the selected Frequency response model, and displayed in the Control name list, enter an input Power spectral density expression. Note that this expression is usually a function of the frequency, freq.

If the correlation type was set as Cross-correlated, fill in expressions for the off-diagonal elements of the cross-correlation between the reduced-order model inputs. These expressions are also typically frequency dependent.