[Nico A.]

Hello everyone,

I computed the flow around a sphere and also calculated the lift and drag forces/ coefficients. At present I got to high values for Cd (0.61) at Re = 1*10⁴, due to the k-epsilon turbulence model I guess.
But anyway I checked the code for the calculation in the 'forceCoeffs.C' file. Most of it is clear to me, but I did not underśtand a few lines:

void Foam::forceCoeffs::write()
00110 {
00111     if (active_)
00112     {
00113         // Create the forces file if not already created
00114         makeFile();
00115 
00116         forcesMoments fm = forces::calcForcesMoment();
00117 
00118         scalar pDyn = 0.5*rhoRef_*magUInf_*magUInf_;
00119 
00120         vector totForce = fm.first().first() + fm.first().second();
00121         vector totMoment = fm.second().first() + fm.second().second();
00122 
00123         scalar liftForce = totForce & liftDir_;
00124         scalar dragForce = totForce & dragDir_;
00125         scalar pitchMoment = totMoment & pitchAxis_;
00126 
00127         scalar Cl = liftForce/(Aref_*pDyn);
00128         scalar Cd = dragForce/(Aref_*pDyn);
00129         scalar Cm = pitchMoment/(Aref_*lRef_*pDyn);

I am not used to the C-language that much, but I want to know what is mathematically done in the red marked lines. Thanks for your advices!

Best regards Nico