# Surface element set self contact

**URL:** <https://calculix.discourse.group/t/surface-element-set-self-contact/425>\
**Category:** Uncategorized\
**Created:** [February 4, 2021, 4:13am UTC](https://calculix.discourse.group/t/surface-element-set-self-contact/425 "2021-02-04T04:13:10Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![mtree](https://avatars.discourse-cdn.com/v4/letter/m/9e8a1a/32.png) [@mtree](https://calculix.discourse.group/u/mtree)\
**Post date:** [February 4, 2021, 4:13am UTC](https://calculix.discourse.group/t/surface-element-set-self-contact/425/1 "2021-02-04T04:13:10Z")

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I’m attempting to couple CaculiX with OpenFOAM via preCICE to simulate 2-way FSI for a heart valve. As the fluid pressure forces the valve open, contact is handled by a single contact pair between the downstream surface of the valve leaflets and the blood vessel wall. However, when the pressure gradient flips to close the valve the upstream surface of the valve will come in contact with itself. How can I properly model this contact? Is it as simple as defining a contact pair between the upstream surface and itself?

I’m working with CalculiX 2.16, in case that matters.

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**Author:** ![SergioP](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/sergiop/32/10_2.png) [@SergioP](https://calculix.discourse.group/u/SergioP)\
**Post date:** [February 4, 2021, 6:53pm UTC](https://calculix.discourse.group/t/surface-element-set-self-contact/425/2 "2021-02-04T18:53:22Z")

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You can define only one surface set including both sides of the contact and make a contact pair calling the same surface set for master and slave, see the example

 ![2021-02-04 15_48_31-Mi Teamcenter - Teamcenter Express](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/59df2d935ca2409c373dcce685c63cc71a998491.png)

 ![2021-02-04 15_49_55-rubber_bellow.liml - Mecway](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/cf8bbb65746e107c7656775cf0dd3282d9b25fbc.png)

![2021-02-04 15_52_33-rubber_bellow.inp - SciTE](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/2c89f84889b7553b0b3e7ab11a85662ba7dca0aa.png)

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**Author:** ![shc](https://avatars.discourse-cdn.com/v4/letter/s/90db22/32.png) [@shc](https://calculix.discourse.group/u/shc)\
**Post date:** [October 27, 2023, 6:43am UTC](https://calculix.discourse.group/t/surface-element-set-self-contact/425/3 "2023-10-27T06:43:45Z")

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Hi mtree,

I am interested in such a case. Have you managed to simulate heart valve and newtonian blood behaviors in a 2 ways FSI simulation with contact thanks to OpenFOAM/CalculiX/preCICE?

Any leakage or instability issues?

Thank you in advance,