The following limitations apply to
FLUENT's FFT module:
FLUENT FFT module can only read inputs files in the
FLUENT monitor and x-y file formats.
FLUENT FFT module assumes that the input data have been sampled at equal intervals and are consecutive (in the order of increasing time).
The lowest frequency that the FFT module can pick up is given by
is the total sampling time. If the sampled sequence contains frequencies lower than this, these frequencies will be aliased into higher frequencies.
The highest frequency that the FFT module can pick up is
is the sampling interval (or time step).