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Forum: Main CFD Forum

May 15, 2014, 11:26

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

did you performed the statistical average of...

did you performed the statistical average of correlations along the z (spanwise values), but what about the position y in the channel height?
Please, show a figure with the comparison ...

Forum: Main CFD Forum

July 10, 2013, 13:28

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

of course you have (1/N) in the mean... the...

of course you have (1/N) in the mean...

the ifft of E produce the correlation, hence you have to scale if you want the coefficients. But I don't think that scaling is something that can add more...

Forum: Main CFD Forum

July 10, 2013, 12:38

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

The better the resolution, the wider will be the...

The better the resolution, the wider will be the spectrum, hopefully you will see the dissipative decayding part that here is not shown. It seems that you have until a maximum frequency of about 40...

Forum: Main CFD Forum

July 10, 2013, 03:41

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

well, consider that this is the only snapshot (I...

well, consider that this is the only snapshot (I think related to some time measurement), in general the spectrum is statistically averaged. As you are studyng a pulsatile flow this average should be...

Forum: Main CFD Forum

July 9, 2013, 06:01

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

good, let me see some plots ;)

good, let me see some plots
;)

Forum: Main CFD Forum

July 8, 2013, 18:14

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

it is simple using the FFT, take your velocity...

it is simple using the FFT, take your velocity vector v(1:M,y0) and compute the Fourier coefficients C(Kx,y0), then compute the modulus of the coefficients and plot along Kx. Use a logarithmic scale...

Forum: Main CFD Forum

July 8, 2013, 14:28

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

well, you can also compute directly the energy...

well, you can also compute directly the energy spectrum and then compute the correlation by means of the inverse transform...however, even the spectrum alone is sufficient to check for...

Forum: Main CFD Forum

July 8, 2013, 14:08

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

you have 2d data from experiment or simulation?...

you have 2d data from experiment or simulation? Correltations in 3d are quite different...
However, if you have a periodic condition along x you can simply compute the spectrum at y=y0, that is...

Forum: Main CFD Forum

July 8, 2013, 13:18

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

ok, I see... therefore: 1) you have the...

ok, I see... therefore:

1) you have the separation variable r sampled on the x-direction grid, r(i)=i*dx, i=1,...,M-1, note that r(M-1)=(M-1)dx;
2) what about the third dimension?
3) are you...

Forum: Main CFD Forum

July 8, 2013, 06:16

Replies: 21

2-point spatial velocity correlation

Views: 11,681

Posted By FMDenaro

Hi, I am not sure to get exactly your question,...

Hi,
I am not sure to get exactly your question, however when you fix x=x0 then:

R(x0,r)=<Vi'(x0)Vi'(x0+r)>/sqrt(<Vi'(x0)^2> = F(r)

is a function only of the separation lenght r. Therefore you...

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