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-   -   integral length scale and cross-correlation (with openfoam data, LES pipe flow) (https://www.cfd-online.com/Forums/main/76782-integral-length-scale-cross-correlation-openfoam-data-les-pipe-flow.html)

jet June 4, 2010 08:07

integral length scale and cross-correlation (with openfoam data, LES pipe flow)
 
Hi,
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(i)=uflukt(1)*uflukt(i)
end
ucross=ufluct./ufluct(1);
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.:confused:
i have read some books about it (Pope, Wilcox, Hinze and Lumley ...) but i can't implement their ideas in matlab.:mad:

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

jet

lx882211 November 7, 2016 05:23

Hi, can you tell me how to calculate intergral scale, based on Openfoam data? Thank you very much.


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