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FFT with non-uniformly distributed data

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Old   May 18, 2013, 00:31
Default FFT with non-uniformly distributed data
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Kai Zhang
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hi everyone
I'm using the adjustTimeStep in pimpleFoam to do my simulation, so my timestep is not uniform. After the calculation I need to get the frequency of the lift force, but as the force data is not evenly distributed, it seems difficult to do this. I tried using linear interpolation to convert the data into uniform one, but there seems to be some discrepancy.
does anyone have any idea on how to do this?
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Old   May 20, 2013, 21:17
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Kyle Mooney
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Quote:
Originally Posted by kkpal View Post
hi everyone
I'm using the adjustTimeStep in pimpleFoam to do my simulation, so my timestep is not uniform. After the calculation I need to get the frequency of the lift force, but as the force data is not evenly distributed, it seems difficult to do this. I tried using linear interpolation to convert the data into uniform one, but there seems to be some discrepancy.
does anyone have any idea on how to do this?
Matlab recommends using interpolation:

http://www.mathworks.com/support/sol...lution=1-15NDN

Not sure what kind of discrepancy you're seeing...You could always change the way the time steps are written to force them to be uniform and that would solve your problem.
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Old   May 21, 2013, 02:35
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thanks Kyle.
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