# How to define ball clump contacts in PFC

**URL:** <https://forum.itascainternational.com/t/how-to-define-ball-clump-contacts-in-pfc/851>\
**Category:** PFC\
**Tags:** fish, suggestions\
**Created:** [December 5, 2022, 3:16am UTC](https://forum.itascainternational.com/t/how-to-define-ball-clump-contacts-in-pfc/851 "2022-12-05T03:16:18Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Ahmed2021](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Ahmed2021](https://forum.itascainternational.com/u/Ahmed2021)\
**Post date:** [December 5, 2022, 3:16am UTC](https://forum.itascainternational.com/t/how-to-define-ball-clump-contacts-in-pfc/851/1 "2022-12-05T03:16:18Z")

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Hi everyone,

I have a model consisting of an assembly of balls and within this assembly, I am creating pebbles arranged on a certain path. When I let the model run to reach equilibruim, the balls penetrate through the pebbles without being arranged around it. The clump particles represent a hole in the assembly however the balls are not identifying the clump particles at all even though I defined ball-pebble contact linear model. Is there anything I am missing. I am grateful for any help.

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**Author:** ![Ahmed2021](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Ahmed2021](https://forum.itascainternational.com/u/Ahmed2021)\
**Post date:** [December 12, 2022, 4:18pm UTC](https://forum.itascainternational.com/t/how-to-define-ball-clump-contacts-in-pfc/851/2 "2022-12-12T16:18:01Z")

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Is there any suggestions please how to include ball-clump interface and the proper values of the used parameters.

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**Author:** ![dblanksma](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@dblanksma](https://forum.itascainternational.com/u/dblanksma)\
**Post date:** [December 12, 2022, 4:26pm UTC](https://forum.itascainternational.com/t/how-to-define-ball-clump-contacts-in-pfc/851/3 "2022-12-12T16:26:23Z")

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Did you specify a ball-pebble default contact type in the cmat? In Help in Documentation see _PFC \> Examples \> Tutorials \> Using the CMAT_ for a good example on this topic.

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**Author:** ![Ahmed2021](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Ahmed2021](https://forum.itascainternational.com/u/Ahmed2021)\
**Post date:** [December 12, 2022, 4:30pm UTC](https://forum.itascainternational.com/t/how-to-define-ball-clump-contacts-in-pfc/851/4 "2022-12-12T16:30:52Z")

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Thank you for your comment. I did check this example however it never mention contact model between ball-pebble at all. I tried on my own several tries to define it however the clumps are randomly distributed over the domain space. I don’t know the right procedure to define them. I hope you can help me out. Thanks again

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**Author:** ![dblanksma](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@dblanksma](https://forum.itascainternational.com/u/dblanksma)\
**Post date:** [December 12, 2022, 4:49pm UTC](https://forum.itascainternational.com/t/how-to-define-ball-clump-contacts-in-pfc/851/5 "2022-12-12T16:49:14Z")

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Hello @Ahmed2021, I see you have sent this inquiry to [PFCsupport@itascacg.com](mailto:PFCsupport@itascacg.com), we will be in contact with you shortly. Thanks!