[MSTEINBUCH]

I tried to get the coefficient Clp - resistance to rolling. I used the cards
GRID_MOVEMENT= ROTATING_FRAME
MACH_MOTION=
MOTION_ORIGIN=
ROTATION_RATE=

Expected to get Clp by dividing the result CMX by ROTATION_RATE input but the result was far from expected

Please Help

[bigfootedrockmidget]

Can you give the definition of the resistance to rolling?


CM is simply computed using all contributions of this form in all nodes:
CMx += (Force[2] * MomentDist[1] - Force[1] * MomentDist[2]) / RefLength;
with pressure forces given as:
Force[iDim] = -(Pressure - Pressure_Inf) * Normal[iDim] * factor * AxiFactor;


with factor being 1/(0.5 * Density_Inf * RefVel2 * config.GetRefArea())


So if the definition of Cl_p = CM / rotation-rate, even then it can be tricky to get the right value since you have to correctly set all the reference values.

[MSTEINBUCH]

Rolling dumping moment results from differences of angles of attack between right wing and left wing due to rotation. (Hope attached successfully the picture).
A section of the right wing located a distance y from the centerline will experience an increment in its angle of attack because of P, given by =Py/V

A rough estimation of the damping moment coefficient for simple tapered wing is given by Clp= -a0/12*(1+3)/(1+), where a0 is wing lift slope and lamda is (tip cord)/(root cord).

Wondering if use of normalized roll rate p*SPAN/(2VREF) instead of rad/sec for ROTATION_RATE will fix the problem