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integral length scale and cross-correlation (with openfoam data, LES pipe flow)

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Old   June 4, 2010, 08:07
Default integral length scale and cross-correlation (with openfoam data, LES pipe flow)
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i want to calculate the integral length scale of a pipe flow in matlab.
the pipe flow (LES) is calculated with openfoam-1.6 .
I have read out the velocity components (cell center) of 1000 cells in a preview-folder at a one definite time-step.
Now I have to calculate the cross-correlation function (in x-direction):
1. step: i subtract the mean velocity from the axial-velocity-component in order
to obtain the fluctuating velocity u'

2. step: i calculate the cross-correlation as:

for i=1:1:1000;
ufluct is the same as u' and ucross should be my cross-correlation coefficient?!
but my problem is, my code does not calculate the time-averaged cross-correlation-coefficient because i don't know wich kind of data i have to time-averaged.
i have read some books about it (Pope, Wilcox, Hinze and Lumley ...) but i can't implement their ideas in matlab.

it would be great if somebody has an idea or could explain me how to calculate the integral length scale correctly!
best regards,

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