unsymmetry force meaning

Yang_QI1

Hi,

I am writing EDEM conatact force API and got confused in the main function calculateForce(). We have two function addNormalForce() and addUsNormalForce() to return the results. What are the difference between them? When I am using addUsNormalForce(), will element 1 receive a force while element 2 receive an opposite force with same magnitude, similar to addNormalForce()? What's more, I would like to know how they are related to energy loss calculation.

Regards,

Qi

Stephen Cole

Hi Qi,

addNormalForce() is used to add the total resultant force calculated from the contact model.  This is typically the undamped force + damping component.  This force ultimately influences the motion of the material.

addUsNormalForce()  is used to return the damping component of the force only.

For the normal and tangential forces each particle always receives equal and opposite force values.

In the EDEM Analyst only the undamped force (normal force - USNormalForce) is reported.

The reason for this is the real physical force at the contact is the undamped spring force, the damping is an approximation in DEM so the convention is that the 'real' force is reported.

There is some discussion on the energy loss models here:

https://community.altair.com/community/en/edem-api-contact-model-example-energy-loss?id=kb_article&sysparm_article=KB0121821

Regards

Stephen