Energy spectrum in frequency

bhigahAshish · July 5, 2019, 07:59

Hi I am trying to calculate the Energy spectrum, which is a concept usually applied to the wavenumber, but I want to calculate an energy spectrum in frequency.

In order to do that I calculated the autocorrelation function of 3 component of velocity in one point. I did the psd of the 3 component using the autocorrelation function not normalised.
Then I summed them and I divided these by two. So It is respected the fact that the mean value of turbulent kinetic energy is equal to the integral of the energy spectrum over the frequency.

do you think that this approach can be acceptable in order to calculate the energy spectrum in frequency?

FMDenaro · July 5, 2019, 08:27

Quote:

Originally Posted by bhigahAshish

Hi I am trying to calculate the Energy spectrum, which is a concept usually applied to the wavenumber, but I want to calculate an energy spectrum in frequency.

In order to do that I calculated the autocorrelation function of 3 component of velocity in one point. I did the psd of the 3 component using the autocorrelation function not normalised.
Then I summed them and I divided these by two. So It is respected the fact that the mean value of turbulent kinetic energy is equal to the integral of the energy spectrum over the frequency.

do you think that this approach can be acceptable in order to calculate the energy spectrum in frequency?

frequency and wavenumber is almost the same since k=n*2*pi/L

bhigahAshish · July 5, 2019, 08:33

Yes, it is what I was thinking. So this approach can be acceptable?

ngerma · July 7, 2019, 07:58

Quote:

Originally Posted by FMDenaro

frequency and wavenumber is almost the same since k=n*2*pi/L

Thanks I was using this computation but I'm hesitant same reason for the OP if it's acceptable.

bhigahAshish · July 7, 2019, 10:54

Quote:

Originally Posted by ngerma

Thanks I was using this computation but I'm hesitant same reason for the OP if it's acceptable.

Hi, which reasons make you hesitant?

July 5, 2019, 07:59	Energy spectrum in frequency	#1
bhigahAshish Member Ashish bhigah Join Date: Jan 2019 Posts: 31 Rep Power: 7	Hi I am trying to calculate the Energy spectrum, which is a concept usually applied to the wavenumber, but I want to calculate an energy spectrum in frequency. In order to do that I calculated the autocorrelation function of 3 component of velocity in one point. I did the psd of the 3 component using the autocorrelation function not normalised. Then I summed them and I divided these by two. So It is respected the fact that the mean value of turbulent kinetic energy is equal to the integral of the energy spectrum over the frequency. do you think that this approach can be acceptable in order to calculate the energy spectrum in frequency?

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July 5, 2019, 08:33		#3
bhigahAshish Member Ashish bhigah Join Date: Jan 2019 Posts: 31 Rep Power: 7	Yes, it is what I was thinking. So this approach can be acceptable?