Eliminating inital transient in CFD-post FFT analysis

pz21 · October 7, 2013, 23:03

Dear all,

I'm trying to extract the frequency of oscillating in vortex shedding simulation, and to exclude the irregular drag and lift force data in inital transient to get a better FFT result.
The checkbox "Full range of input data" in Fast Fourier Transform, "General" tab of Chart seems allow a specified time range selection of data, but it doesn't show any effect on the FFT result when I change the value of "Min" and "Max". The explanation of this checkbox in ANSYS Help Document is so rough that I cannot find out why it doesn't work. Does any body know if there is something wrong with my operation? Or if I have a misunderstanding of the function of this checkbox?

Thanks a lot
pz21

ghorrocks · October 8, 2013, 05:29

I have never used that function so cannot help you much. It is a new feature and I am a very old person

I just export the data and do the FFT in a package like matlab or python or something like that.

pz21 · October 8, 2013, 05:44

Quote:

Originally Posted by ghorrocks

I have never used that function so cannot help you much. It is a new feature and I am a very old person

I just export the data and do the FFT in a package like matlab or python or something like that.

The FFT feature in CFD-post seems a little rough with only few input parameters. I'm looking for a free software package with FFT capability.
Thanks again for your kindly reply Glenn.

ghorrocks · October 8, 2013, 05:46

Free FFT software: Octave, python+(numpy or scipy)

pz21 · October 8, 2013, 05:59

Quote:

Originally Posted by ghorrocks

Free FFT software: Octave, python+(numpy or scipy)

Thank you very much!

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October 8, 2013, 05:29		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,327 Rep Power: 138	I have never used that function so cannot help you much. It is a new feature and I am a very old person I just export the data and do the FFT in a package like matlab or python or something like that.

October 8, 2013, 05:46		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,327 Rep Power: 138	Free FFT software: Octave, python+(numpy or scipy)