Calculating the Spectral Density
To calculate the spectral density, you create a line time history, a line time Fourier transform, and a derived data set. You can then visualize the spectral density.
To create a line time history to record data from the line probe:
- Right-click the node and select the .
- Right-click the New derived data from probe part on surface. node and select
-
Select the
node and set the following properties:
Property Setting Field Function 1 Pressure Data Surfaces 1 Plane section Part line-probe Representation cylinderPressureData Update Active Activated
To create a line time Fourier transform:
- Right-click the node and select .
- Rename the newly created Gxx(l). node to
- Select the node and make sure Amplitude Function is set to .
To create the derived data set node into which you import the data:
- Right-click the New derived data from derived data. node and select
- Rename the newly created Power Spectra. node to
-
Select the
node and set the following properties:
- Set Input time history to Multi-Point Time History.
- Activate Update Active. All other properties are disabled for editing and updated automatically after you activate Update Active.
To visualize the spectral density:
With the Update Active property activated, the Fourier transform is automatically calculated once you assign the last property. This process takes a few minutes, depending on the processor speed of your computer.
When the Fourier transform has been computed, you visualize the spectral density as a function of distance. You use a logarithmic scale for the spectral density axis.
- Create a monitor plot and rename it to Power Spectra .
- Right-click the Add Data. node and select
-
In the Add Data Providers to Plot dialog,
expand Derived Data and select Power Spectra.
The plot of Power Spectral Density against Distance appears in the graphics window.