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Search took 0.00 seconds. Search: Posts Made By: gregor
Forum: OpenFOAM August 13, 2012, 04:45
Replies: 19
Views: 5,942
Posted By gregor
In step 1 in the pdf file you plug in the old...

In step 1 in the pdf file you plug in the old variance and the old mean value gets cancelled out. This means you are alway using the current mean value. The current mean value is correct but only up...
Forum: OpenFOAM January 24, 2012, 12:36
Replies: 19
Views: 5,942
Posted By gregor
Yes i guess it is the same reason why you...

Yes i guess it is the same reason why you calculate the average by

<phi> = alpha*<phi>_{i-1} + beta * phi

instead of using

phiS += phi

phiA = phi/N
Forum: OpenFOAM January 24, 2012, 11:56
Replies: 19
Views: 5,942
Posted By gregor
You could try it by evaluting it manually. The...

You could try it by evaluting it manually. The point is you want to have a variance every time step but your final mean value is unknown, therefore you take the current mean value. But once you use...
Forum: OpenFOAM January 24, 2012, 11:41
Replies: 19
Views: 5,942
Posted By gregor
So do it the other way round and look if can...

So do it the other way round and look if can derive it from the algorithm



look what happens in the addMeanSqrToPrime2Mean function.



sigma_{i-1} = sigma_{i-2} + <phi>^2_{i-1}
Forum: OpenFOAM January 24, 2012, 10:13
Replies: 19
Views: 5,942
Posted By gregor
i will look through equations when i find some...

i will look through equations when i find some time, in the meanwhile you can have a look at my document.

But i think the problem is that you don't consider the mean value as a "on the fly value"...
Forum: OpenFOAM January 24, 2012, 07:59
Replies: 19
Views: 5,942
Posted By gregor
No it shouldn't they're using the ...

No it shouldn't

they're using the following identy:

1/(n)sum^n(phi_i-<phi>)^2=1/n*sum^n(phi_i^2)-<phi>^2 , where <.> is an averaged value
...
Forum: OpenFOAM July 1, 2011, 06:45
Replies: 19
Views: 5,942
Posted By gregor
how can i delete a post ?

how can i delete a post ?
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