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Energy Spectrum in Three Dimension?

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Old   May 23, 2020, 21:27
Default Energy Spectrum in Three Dimension?
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Farzad Faraji
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Energy Spectrum in Three Dimension?

Dear Friends
I want to do 3D spectral analysis for energy. My domain is rectangular and it is (0,0,0)*(0.5, 1.0, 0.1), and it is almost like a jet flow(rectangular bubble flow).
Now my question is that for FFT, my nodes needs to be equal(Nx=Ny=Nz) OR mesh size needs to be equal(dx=dy=dz)?

Thanks,
Farzad
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Old   May 24, 2020, 04:38
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Filippo Maria Denaro
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Originally Posted by farzadmech View Post
Energy Spectrum in Three Dimension?

Dear Friends
I want to do 3D spectral analysis for energy. My domain is rectangular and it is (0,0,0)*(0.5, 1.0, 0.1), and it is almost like a jet flow(rectangular bubble flow).
Now my question is that for FFT, my nodes needs to be equal(Nx=Ny=Nz) OR mesh size needs to be equal(dx=dy=dz)?

Thanks,
Farzad



You need one or more directions of periodicity and equal step size along such direction
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Old   May 24, 2020, 12:14
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Farzad Faraji
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Dear professor Denaro
Based on what you said for powerspectrum in 3D(rectangular), I need to have dx=dy=dz. But what about Nx(kmax=Nx/2 based on Nyquist theory). Since my Ny is larger than Nx what should I do?(Ny is my streamwise direction).

And let ask me a radical question;
Can I just transfer rectangle to square and do the powerspectrum inside the square?

Thanks,
Farzad

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You need one or more directions of periodicity and equal step size along such direction
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