Determining the Group Velocity of the Disturbances

A wavenumber-frequency diagram (or fk plot) is used to determine the group velocity at which disturbances propagate along the domain.

To determine the group velocity for this simulation, first compute cross spectral densities or auto spectral densities using the data from the .simh file. Determine the range for which the data is meaningful for analysis and use this range to compute a line spatial Fourier transform. By plotting the spectra from this Fourier transform, you can compute the group velocity of the disturbances.

This section describes the steps for doing so:

  1. Creating a line probe along which transient data is extracted.
  2. Creating a line time history to record data from the line probe.
  3. Calculating the spectral density along the line probe.
  4. Calculating the line spatial Fourier transform and using it to determine the group velocity.