29.11.1 Limitations of the FFT Algorithm

The following limitations apply to ANSYS FLUENT's FFT module:

• The ANSYS FLUENT FFT module can only read inputs files in the ANSYS FLUENT monitor and x-y file formats.

• The ANSYS 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 $1/t$, where $t$ 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 $1/(2dt)$, where $dt$ is the sampling interval (or time step).