Extracting F-X Spectra to a .simh File

Use the following steps:

  1. Create a plane section in derived parts, then create a history file (.simh) under Solution Histories and use the previously created plane section as the input part. See below for an example of solution history settings.


  2. Run the simulation, then save the .sim file. This action also saves the .simh file, and creates a recorded solution view and solution representation. The solution view and representation import the data from the .simh file.
  3. Create a line probe on the plane section from the CAE model. Keep the line points equally spaced and close to cell centers to reduce interpolation error, as shown below.


  4. Map the .simh file into the Line Time History object:
    1. Right-click the Tools > Data Set Functions node and select New > Line Time History (h[l]).
      The h(l) node appears under Data Set Functions. This node stores the history on the line. Rename if desired.
    2. Right-click the h(l) > Imported node and select New derived data from imported surface and derived part. The node Multi-Point Imported opens below.
    3. Select Multi-Point Imported and set the following properties:
      Property Setting
      Field Function 1 Time History:Pressure
      Data Surfaces 1 plane section
      Representation solution representation
      Part line probe
      Update Active Activated
  5. Right-click the Tools > Data Set Functions node and select New > Line Time Fourier Transform (G[h[l]]).
    Time-steps must be equally spaced for this step to work properly.
    The G[h[l]] node appears under Data Set Functions. This node stores the spectrum from history h(l) on the line. Rename if desired.
  6. Right-click the G[h[l]] > Imported node and select New derived data from derived data.
  7. Select Multi-Point Imported and set the following properties:
    Property Setting
    Input Time History G[h[l]] under its current name
    Update Active Activated
  8. Select Output control under G[h[l]] and set 3D profile type to the G[h[l]] node under its current name. This stores an F-X spectra surface, plotting frequency vs. distance.
  9. In post-processing, create a scalar scene.
  10. Select the derived data using the Parts property of the scalar displayer.
    1. Select the Scalar 1 > Parts node.
    2. In the Properties window, click the property customizer button for the Parts property.
      The Parts dialog appears.
    3. Select the derived data set.
    4. Click OK.
  11. Select the Scalar Field node and set its Function to the derived data.
The spectra contour is displayed in the scalar scene window. In the following example, the dominant frequency mode is around 900 Hz.

Repeat these steps with line probes in different positions, or after changing the position of the existing probe, to get a more comprehensive picture of the frequency distribution.

See also the Signal Post-Processing tutorial.