Question about damping force and damping torque?

Raheem Sterling_22160

Hi

（1）In order to reach the quasi-static quickly, I want to introduce the damping force and torque into the contact model, according to the Cbonded.cpp, the F_bond_n_damp was added to the contactResults.normalForce, and rolling friction was added to the contactResults.additionalTorque1 and contactResults.usadditionalTorque1 together, I know the  usadditionalTorque1 can be used for the energy loss, does it mean that any torque I want to used for the energy loss can be added to the usadditionalTorque1 which has no influence on the motion of particle?

（2）In HM model and bondv2 model, the normal direction was calculted by the code as below:

// relative velocity of both surfaces at contact point     CSimple3DVector relVel = element1.velocityAtContactPoint - element2.velocityAtContactPoint;     CSimple3DVector unitCPVect = contact.contactPoint - element1.position;     unitCPVect.normalise();      //I'm going to assume that the physical and contact radius are the same for this model.     CSimple3DVector relVel_n = unitCPVect * unitCPVect.dot(relVel);     CSimple3DVector relVel_t = relVel - relVel_n;

but in my model, the direction of normal bond force was not consistent with "relVel_n", so should I return the normalForce in the direction with my own direction or as the same as the HM or bondv2?

Thanks for help.

Regards!

Stephen Cole

Hi Raheem,

If you want to actually damp the torques I'd add it to additionalTorque1 and additionalTorque2, the usadditionalTorque is more for the post-processing of the energy losses.

 

For the normal forces it would be unusual for them not to be opposing the velocity direction however you can apply them in any direction.  In the code you describe the unitCPVect is calculated to obtain a normal and tangential direction which has X,Y,Z components in global space.  This then allows the normal force to be applied in the global space but with with normal vector.  For the customisation you can apply the force in any direction.

Regards

Stephen