[farzadmech]

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

[FMDenaro]

Originally Posted by farzadmech

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

[farzadmech]

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

Originally Posted by FMDenaro

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