|February 17, 2014, 14:17||
Fast Fourier Transform (FFT) in Tecplot 360
Join Date: Jan 2014
Posts: 5Rep Power: 4
I am trying to use Tecplot 360 to get the frequency of my wave. I am using the "Fourier Transform" tool in the "Data" menu. For the plot that gets output, the frequency I am getting looks correct but the amplitude is way higher than the amplitude of my wave.
What is problem here? Does anybody know the exact fourier equation that Tecplot 360 uses?
|May 11, 2014, 05:41||
Join Date: Jan 2010
Location: CFD Lab
Posts: 118Rep Power: 8
We have encountered the same problem in Tecplot.
The Trend of the output graph and the frequency are very similar to the results obtaind using Excel but the amplitude is very high.
If we use different Window function (Rectangular, Triangular, Hann, Hamming) then different amplitudes are obtained but all of them are very High.
Have you solved this problem?
Thanks in advance
“If you have an apple and I have an apple and we exchange these apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas.”
|May 12, 2014, 12:01||
Join Date: May 2014
Location: Bellevue, Washington
Posts: 13Rep Power: 4
Tecplot 360 uses FFTW to perform the FFT calculation.
As with most DFT's a gain or scaling factor is introduced. We have chosen to leave the calculation as is and let the user decide if they need it scaled down. If you divide the amplitude by your sampling size, you should receive a more reasonable value. You can use the Data > Alter > Specify Equations tool to do this.
|fast fourier transform, fft, fourier, tecplot 360|
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