# forces: What are magUInf, lRef, Aref?

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 March 6, 2011, 16:07 forces: What are magUInf, lRef, Aref? #1 Senior Member   Klaus Join Date: Mar 2009 Posts: 101 Rep Power: 10 Sponsored Links Hello, I want to optimise a wing, hence analyse cl/cd using the forces function but I don't know the meaning of some variables (magUInf, lRef, Aref). Actually my wing is a hydrofoil therefore the high rhoInf = 1000 kg/m3 for water. Her the "draft" entries in my controlDict: functions ( forces { type forces; functionObjectLibs ("libforces.so"); //Lib to load patches (stlSurface); // change to your patch name rhoInf 1000; //Reference density for fluid rhoName rhoInf; CofR (0.15 0 0); //Origin for moment calculations outputControl outputTime; } forceCoeffs { type forceCoeffs; functionObjectLibs ("libforces.so"); patches (stlSurface); //change to your patch name rhoInf 1000; rhoName rhoInf; CofR (0 0 0); liftDir (0 1 0); dragDir (1 0 0); pitchAxis (0 0 0); magUInf 55.5; //? lRef 0.6; //? Aref 1; //? outputControl outputTime; } What are magUInf, lRef, Aref? Klaus

 March 6, 2011, 16:58 #2 New Member     Gregor Seljak Join Date: Oct 2010 Posts: 21 Rep Power: 8 Hi! a.) magUInf is relative velocity between hydrofoil and water. b.) lRef is length of hydrofoil, which is equal to chord length of hydrofoil profile. c.) Aref is area of your hydrofoil, which is chord length*span. If you are doing 2D simulation, then span is equal to z coordinate. ordinary likes this.

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