What's the criteria for positive and negative of force in API

Raheem Sterling_22160
Raheem Sterling_22160 Altair Community Member
edited August 2023 in Community Q&A

Hi

I know the contact.force act on the contact point of particles, and then act on the element1 and element2 is opposite.

In HM model, I saw the equation is image, but in the code, F_n = unitCPVect * -factor, and the F_t is as same as the equation.

For F_n, does it because the unitCPVect = contact.contactPoint - element1.position, and this direction is "-" in the EDEM?

 

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Answers

  • Renan
    Renan
    Altair Employee
    edited August 2023

    Hi Raheem,

    The equation you posted is used to calculate the magnitude of the normal force. Since forces are a vector quantity we also have to specify their direction and since the forces on the Hertz-Mindlin model are repulsive, they have to point in the direction such that the particles are separating, so the "-" sign in the equation is there just to make sure that the forces are actually repulsive.

    Best regards,

    Renan

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