[EDEM] Are the contact forces in EDEM contat API applied at the particle center?

KJHSNU

Hello,

I have a question about the EDEM Contact API. In the Contact API’s "calculateForce" function, I see that NCalcForceTypesV3_0_0::SContactResult& contactResults allows us to add a Bond force. For the forces computed here, are they applied at each particle’s center (center of mass or geometric center), or at the contact point?

For example, inside the calculateForce function, if I calculate a force and update normalForce and tangentialForce, like below, are those forces applied at the particle center (as in the first figure), or are they applied at the contact point (as in the second figure), thereby generating torque?

Code ;

contactResults.normalForce += F_bond_n;
contactResults.tangentialForce += F_bond_t;

Additionally, if the forces are applied at the contact point (the second case), is there a way to have them applied at the particle center as in the first case?

Thank you.

Stephen Cole

Hi,

In the Contact Model the forces are applied at the contact point. So for example any Tangential Force applied at this point results in a Torque based on the distance from the Centre of Mass..

You can't change the point the force or torque is applied, however you can manually apply both a force and torque if you want to create the effect of apply forces at different points (e.g. apply opposing torque).

Or you can apply the forces in a Particle Body Force. The PBF is called every time-step for every particle unlike the Contact Model which is applied for every Contact. Its also a bit more involved but you could store the contact forces as a Particle Custom Property and under the returned force return 0. Then in the PBF, which is called last in the chain, apply this force.

Contact model approach of applying force and torque would be more computationally efficient and easier in the long term, PBF model is simpler to calculate but does require implementation of custom properties, its a useful method for verifying the results however.

Regards

Stephen