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Question: Calculation of relative velocity in EDEM.

Hello everyone:

Thank you for answering my questions, which helped me a lot. I have doubts about the calculation of relative velocity in edem. When I use the H-M model, the calculation of damping force needs to use the relative velocity, which is described in the document as "calculation at the contact point". How do I understand this sentence? Does the calculation of relative velocity consider the angular velocity at the contact point? Or only the translation of particles?

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EDEM

English

v2020.2

Accepted answers

Renan

Hi Yu,

During contact/collision different contact models can take different inputs, however typically (for example Hertz-Mindlin model) the Relative Velocity at the Contact Point is used to calculate the normal and tangential relative velocity of the elements and it does take into account the angular velocity of the particles.

You can see the source code for the Hertz-Mindlin model here - https://community.altair.com/community?id=kb_article_view&sysparm_article=KB0113635

Best regards,

Renan

All comments

Renan

Hi Yu,

You can see the source code for the Hertz-Mindlin model here - https://community.altair.com/community?id=kb_article_view&sysparm_article=KB0113635

Best regards,

Renan

Yu Mu

Hi Yu,

During contact/collision different contact models can take different inputs, however typically (for example Hertz-Mindlin model) the Relative Velocity at the Contact Point is used to calculate the normal and tangential relative velocity of the elements and it does take into account the angular velocity of the particles.

You can see the source code for the Hertz-Mindlin model here - https://community.altair.com/community?id=kb_article_view&sysparm_article=KB0113635

Best regards,

Renan

Thank you for your answer. In this case, can I understand that the "relVel_t" of the H-M model in calculating the tangential damping force refers to the relative velocity, which takes into account the translation of particles and the resultant velocity of particles at the contact point due to rotation?

In this case, is the relative velocity calculated as follows?

Thank you very much for your answer!

Renan

Thank you for your answer. In this case, can I understand that the "relVel_t" of the H-M model in calculating the tangential damping force refers to the relative velocity, which takes into account the translation of particles and the resultant velocity of particles at the contact point due to rotation?

In this case, is the relative velocity calculated as follows?

Thank you very much for your answer!

The relative velocity (relVel in the HM model) takes into account both the translation and rotation of the particle at the contact point. It's calculate 171 of the model

// relative velocity of both surfaces at contact point CSimple3DVector relVel = element1.velocityAtContactPoint - element2.velocityAtContactPoint;

Then the relative velocity is split into two components: one in the normal direction:

 CSimple3DVector relVel_n = unitCPVect * unitCPVect.dot(relVel);

And one in the tangential direction:

CSimple3DVector relVel_t = relVel - relVel_n;

So the relVel_t in the tangential damping force calculation is actually the tangential component of the relative velocity.

Best regards,

Renan