### 14.3.4. Quadrupole Sources

Quadrupole sources are related to turbulence fluctuations in the flow field. The Lighthill stress tensor Equation 14–4, neglecting the pressure fluctuation term, is available from the CFX-Solver and can be monitored in the CFX-Solver Manager. It is not only possible to monitor averaged or minimum and maximum values of the quadrupole sources, but also to monitor individual components of the Lighthill stress tensor. These values can be monitored using monitor points created in CFX-Pre. The monitor point data will appear in the User Points tab in the CFX-Solver Manager. These data can be exported if desired.

#### 14.3.4.1. Exporting Acoustic Quadrupole Data

Quadrupole source data is available for transient simulations only. The Lighthill stress tensor and its components are available to export to results, backup and transient results files. To write the data to file, selecting the Lighthill stress tensor from the list of selected variables is required.

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