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Patch names amp forces functionObject

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Old   February 6, 2009, 09:37
Default Hi all I encountered a prob
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David Hora
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Hi all

I encountered a problem with the forces functionObject. I have a simulation with different patches in the domain. Some of the patches have similar names, e.g.:

BLADE
HUB-BLADE
SHROUD-BLADE


I wanted to calculate the forces acting on the patch "BLADE". Unfortunatelly the forces functionObject adds the forces of all patches with the string "BLADE" in its name.

Additionally I have a question concerning the moments. As far as I understand the code, the moments are calculated with the cell centers:


vectorField Md = mesh.C().boundaryField()[patchi] - CofR_;

vectorField pf =
mesh.Sf().boundaryField()[patchi]*p.boundaryField()[patchi];

fm.first().first() += rho(p)*sum(pf);
fm.second().first() += rho(p)*sum(Md ^ pf);

Wouldn't it be better to use the face centers (mesh.Cf())?


Thanks a lot & best regards
David
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Old   February 6, 2009, 10:03
Default I will look into the patch nam
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I will look into the patch name issue.

mesh.C().boundaryField()[patchi] returns the face centres the same as mesh.Cf().boundaryField()[patchi]

H
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Old   February 6, 2009, 12:24
Default Thanks for the report. I corre
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Mattijs Janssens
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Thanks for the report. I corrected the wild-card matching (in 1.5.x). Now BLADE will match only BLADE. Use "BLADE.*" to match all patches starting with BLADE.
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Old   April 26, 2011, 22:59
Default Help Please!
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Greg Givogue
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Hi,

I realize this is an old post but I'm pretty desperate! I'm having some trouble understanding why I cannot calculate a reasonable centre of pressure when I use the forces and moments function. It is my understanding that centre of pressure (x y z) should be located on the body and that it is related by;

Mx=Fy*z+Fz*y
My=Fx*z+Fz*x
Mz=Fx*y+Fy*x

When I use these relationships I end up with x y z far from the body...

I have also ran the patchIntegrate command for p over the body and it produces a different force than the force function (pressure component)?

I have posted this question Center of Pressure for an Aero Body

but I haven't received any useful feedback.

I appreciate any pointers you can give! Please help.
Greg
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