# Turbulent Channel 1D Energy Spectra Calculation

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 October 23, 2015, 17:13 Turbulent Channel 1D Energy Spectra Calculation #1 New Member   stran1028 Join Date: Oct 2015 Posts: 1 Rep Power: 0 Hello, I have 2 point correlation data for a turbulent channel case and I'm trying to put together a script to compute the 1D energy spectra from this. To verify my script, I'm using both 2 point correlations from DNS runs done by Moser et al (http://turbulence.ices.utexas.edu/data/MKM/chan395/) and trying to recreate their 1D energy spectra. Based on what I've seen in literature, the 1D energy spectra should just be the FFT of the 2 point correlation function. However when I try to do this in matlab using the fft function, I'm not able to match Moser's spectra. A snippet of my matlab code which calculates this is shown below. This was based on the examples shown for the fft function on the matlab website. yhat=fft(Ruu); tmpEuu= abs(yhat/L); Euu = tmpEuu(1:L/2 + 1); Euu(2:end-1) = Euu(2:end-1); Any help would be greatly appreciated! Thank you!

October 24, 2015, 03:38
#2
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Filippo Maria Denaro
Join Date: Jul 2010
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Quote:
 Originally Posted by stran1028 Hello, I have 2 point correlation data for a turbulent channel case and I'm trying to put together a script to compute the 1D energy spectra from this. To verify my script, I'm using both 2 point correlations from DNS runs done by Moser et al (http://turbulence.ices.utexas.edu/data/MKM/chan395/) and trying to recreate their 1D energy spectra. Based on what I've seen in literature, the 1D energy spectra should just be the FFT of the 2 point correlation function. However when I try to do this in matlab using the fft function, I'm not able to match Moser's spectra. A snippet of my matlab code which calculates this is shown below. This was based on the examples shown for the fft function on the matlab website. yhat=fft(Ruu); tmpEuu= abs(yhat/L); Euu = tmpEuu(1:L/2 + 1); Euu(2:end-1) = Euu(2:end-1); Any help would be greatly appreciated! Thank you!

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 Tags correlations, energy spectrum, fft, matlab, turbulent channel flow