# lift, drag and moment coefficients using forceCoeffs

 Register Blogs Members List Search Today's Posts Mark Forums Read

 April 1, 2016, 15:52 lift, drag and moment coefficients using forceCoeffs #1 New Member   Join Date: Mar 2016 Posts: 15 Rep Power: 9 Hello everyone, I am simulating the aerodynamic behavior of a 2D airfoil and trying to find the lift, drag and moment coefficients using forceCoeffs. I found a relevant code online as follows: functions { forces { type forceCoeffs; functionObjectLibs ( "libforces.so" ); outputControl timeStep; outputInterval 1; patches ( wing ); pName p; UName U; rhoName rhoInf; log true; rhoInf 1; CofR ( 0 0 0 ); liftDir ( 0.087 0.996 0 ); dragDir ( -0.996 0.087 0 ); pitchAxis ( 0 0 1 ); magUInf 75.00; lRef 1; Aref 1; } } I had some questions about this code: 1- what is CofR (0 0 0) ? is this the origin of the coordinate system of the whole domain (global coordinate system)? or is it the center of mass of the airfoil !? 2- I know liftDir and dragDir are the direction of the lift and drag forces. How about pitchAxis ( 0 0 1 )? is it the direction of the pitch axis? or is it the position of the pitch axis (if this the position, should I use the global coordinate system)? 3- can anyone please explain lRef 1; and Aref 1; lines for me? what are these lines for? and what should be the value of them? can I leave them as 1? Thank you all and really need your help!

 Tags drag, ift, moment