[lucamirtanini]

Hi all,

I was looking at a result in the validation guide of fds.

In particular, attached you can see the Figure 6.41 of the FDS User Guide, which is named Power spectrum.

As far as I know, this figure was produced using this script.

https://github.com/firemodels/fds/bl...wer_spectrum.m

I have 2 doubts:

1) In the Tenneke, the Power spectral density is defined as the fourier trasform of the autocorrelation. Since the autocorrelation is u(t)*u(t')/u^2, I cannot see in this script where is the t' (time difference) in the script.

2) Furthermore I cannot understand how the attached figure "Autospectral Density" can exhibit the -5/3 scaling in the inertial subrange, since I thought that the -5/3 scaling should be seen only in the nondimensionalised kinetic Energy spectrum, as you can seen in the figure "Chapman 1979" attached.