# Moment coefficient on moving mesh

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 June 19, 2012, 12:08 Moment coefficient on moving mesh #1 Senior Member   Join Date: Apr 2010 Posts: 151 Rep Power: 7 Quick question: I use forces to calculates forces and moments on a moving object. The forces are well calculated, but the moment is not, and I think this is because the center of rotation (CofR) is fixed in system/controlDict: Code: ```functions { forces { type forces; functionObjectLibs ( "libforces.so" ); outputControl timeStep; outputInterval 1; patches (foil); pName p; UName U; rhoName rhoInf; log true; rhoInf 1000; CofR (0 0 0); liftDir (0 1 0); dragDir (1 0 0); pitchAxis (0 0 1); magUInf 0.4; lRef 0.1; Aref 0.002; }``` I know at any time where this point is (can be seen from the dynamicMeshDict), but can forces change its CofR?

 June 19, 2012, 17:15 #2 Senior Member   lore Join Date: Mar 2010 Location: Italy Posts: 463 Rep Power: 9 I don't have much of experience on this but if you know where your CofR is in time, then you can easily evaluate the moment around any other point P: Mp1 = Mp2 + p2p1 x F Where: Mp1 = moment around point p1 Mp2 = moment around point p2 p2p1 = vector going from p2 to p1 F = the force which generates the moment x = cross product

 June 20, 2012, 01:33 #3 Senior Member   Join Date: Apr 2010 Posts: 151 Rep Power: 7 Brilliant!

 Tags cofr, forces, moving mesh

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