Flores contact model

Mariusz Warzecha

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Jul 6, 2023, 4:30:35 AM7/6/23

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Hi everyone,

in the article: Sunday, Cecily, Naomi Murdoch, Simon Tardivel, Stephen R Schwartz, and Patrick Michel. 2020. ‘Validating N-Body Code Chrono for Granular DEM Simulations in Reduced-Gravity Environments’. Monthly Notices of the Royal Astronomical Society 498 (1): 1062–79 there is information, that in CHRONO release 5.0.0 the Flores contact force model was added. In the source code of CHRONO release 8.0.0 it seems that the implementation of this model was removed. Although it is possible to select the Flores contact model, the implementation jumps to the Hook contact model. What was the reason for the removal of the Flores model?

Regards,

Mariusz

Radu Serban

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Jul 6, 2023, 6:21:27 AM7/6/23

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Hi Mariusz,

I believe you are talking about the contact model implemented in the core (sequential) Chrono module (i.e., in CalculateForce() in ChContactSMC.h). The Flores model was not “removed”, but rather never implemented in there (I added a comment in the code that says that).

Cecily used the Chrono::Multicore module and this is where she added the Flores model, which we picked up and included in the official Chrono distribution. That is implemented in function_CalcContactForces() in ChIterativeSolverMulticoreSMC.cpp.

I never got around to also add the Flores model in ChContactSMC. Feel free to submit a pull request with such an addition.

--Radu

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Mariusz Warzecha

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Jul 10, 2023, 9:03:48 AM7/10/23

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Hi Radu,

Thanks for your reply. You were right, now I found the implementation without problems. I was wondering how it was written, as the Flores model was developed for two body impacts and it uses the initial, relative impact velocity to calculate the damping factor, which is often problematic to do "a priori" (for example, when one of the impacting bodies is in contact with a third one). From my understanding of the code, except for the cases when ChSystemSMC::TangentialDisplacementModel::MultiStep is set True, the implementation uses characteristic velocity, which is a real number set for the system (the class constructor initiates it with 1). Is it a simplification/approximation or I misunderstood something in the code ?

I have one more question to ask. Have you considered the implementation of contact force models using plastic deformation to express energy dissipation ?