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Old   February 13, 2010, 08:53
Default reference area
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Andrea Pasquali
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Hi,
Is there in OF a code to calculate the frontal area "Aref" (for example the car frontal area) to calculate Cx and Cz using "forceCoeffs" function?

Thanks,
Andrea
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Old   February 14, 2010, 10:33
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Andrea Pasquali
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Hello,
I found "liftDrag" application for OF1.4.
I try to compile it on my OF 1.6.x without success...
Does any version exist for OF1.6 or 1.6.x ?
Does this application calculate the frontal area "Aref" ?

Thanks for any help!

Andrea
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Old   May 5, 2010, 10:41
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Louis Gagnon
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Hi Andrea,

I am also looking for a way to easily calculate the frontal area of a complex 3D body. So far, it seems the only way to do it would be to sum the (area vectors dot the normal vector) on a whole physical surface and ignore negative values (to avoid having a zero total area!).

The code involved would look something like
Code:
mesh.Sf().boundaryField()
but I don't have time to do it at the moment.
and a loop like
Code:
forAllConstIter(labelHashSet, patchSet_, iter)
I'm just inspriring myself from the forces code....

Best regards,

-Louis
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Old   May 17, 2010, 20:13
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Louis Gagnon
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I have looked into it some more and here's the exact command that will give you the frontal area (in x-direction)...

Code:
Info << "***********" << ( sumMag(Sfb[patchi].component(vector::X))/2 ) << "***************" << endl;
I'll get back with an actualy utility for this if I find the time to make one,


-Louis

EDIT: that formula only works if the part has no concavity (ie: holes inside) because this would count areas that should not be counted...

Last edited by louisgag; May 18, 2010 at 16:19.
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Old   June 10, 2010, 02:20
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Björn Bergqvist
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in the meantime, just do like this:
http://www.discretizer.org/node/20

Björn
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Old   August 4, 2010, 16:55
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Louis Gagnon
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thanks for this very useful link. Just a note, if your shape contains some concavities you need to select cells through (or actually skip the extract selection step) and then divide the final result by two.

Cheers,

-Louis
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Old   August 5, 2010, 04:31
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hi louisgag,

Total area can be calculated using the liftdrag utility in OpenFOAM 1.4.1 by running liftDrag and put the same area at the end of controlDict of OpenFOAM 1.6....

Regards,

Naveen
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Old   August 5, 2010, 13:00
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Louis Gagnon
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Thanks Naveen.
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