[sampaio]

Hi All,

In the calcEk function used in DNSFoam, the Ek is calculated as follows:

graph calcEk
(
const volVectorField& U,
const Kmesh& K
)
{
return kShellIntegration
(
fft::forwardTransform
(
ReComplexField(U.internalField()),
K.nn()
),
K
);
}

In text books, however, I always see something involving spectrum Phi{ij}, which is the Fourier transform of the correlation function R.

So we should have R (autocorrelation of u) instead of U inside fft::forwardTransform, something like this:
fft::forwardTransform
(
ReComplexField(autocorrelation_of_U.internalField( )),
K.nn()
),
K

Is that right?

Is there something I am missing?

Something that makes both ways of calculating this spectrum equivalent, that I am missing?

Best regards,
luiz