[s.m]

Hi all,
as you know in the path "/opt/OpenFOAM/OpenFOAM-2.2.x/tutorials/incompressible/pimpleDyMFoam/wingMotion"
there is an example for analyzing the flow over an airfoil, in it's controlDict you can find a function that is defined to give force on the airfoil, we also have similar function to give us the force Coefficient.
functions
{
forces
{
type forces;
functionObjectLibs ( "libforces.so" );
outputControl timeStep;
outputInterval 10;
patches (wing);
pName p;
UName U;
rhoName rhoInf;
log true;
rhoInf 1;
CofR (0.4974612746 -0.01671895744 0.125);
}
}
my Question is about "Cof R"
what CofR is?
how should we intruduce it ? as you see, it doen't write cofR (0 0 0) , hoe these values "0.4974612746" & "-0.01671895744" & "0.125" compute?

[immortality]

hi Saeideh
Its only "center of rotation"
Select aerodynamic center or where you know by your reference.
How did you resolved the problem of resonance of Cl and Cd diagrams(that coeffs in slat were not so good)?

[s.m]

Originally Posted by immortality

hi Saeideh
Its only "center of rotation"
Select aerodynamic center or where you know by your reference.
How did you resolved the problem of resonance of Cl and Cd diagrams(that coeffs in slat were not so good)?

Thanks Ehsan,
would you please tell me what is A, B, C in CofR (A,B,C) is?
i read that in subsonic airfoil, ayrodynamic center is located in c/4, but in abbott's book that i want valid my results, there is two figure for moment coeifficient of naca 4412 at Re=3*10e6 ; 1-for c/4 and 2- for ayrodynamic center.
if we have the coordinate for ayrodynamic center, e.g a.c =( x=0.2, y =-0.6)
we should write them in cofR in this way: cofR = (x=0.2, y=-0.6, 0)?

[immortality]

Hi Saeideh
yes I've seen those figures.I can't remember the reason but can ask for you.
yes I think it should be written as you said.test it and let me know.

[s.m]

Originally Posted by immortality

Hi Saeideh
yes I've seen those figures.I can't remember the reason but can ask for you.
yes I think it should be written as you said.test it and let me know.

Hi,Ehsan
Thank you very much
actually i get a better result for cm by setting the " CofR(0.72 0 0) // Axle midpoint on ground" than setting the cofR(0.245 -0.068 0) for NACA 4412.
for first setting cm= -0.09
for second one cm= 0.1

[mowei]

Hi, everyone!
I want to ask a question about Cof, if the wing moves up and down, how should I set the Cof, still keep a fixed value? Can anyone help me solve the question?