# Internal flow Region errors

**URL:** <https://www.simscale.com/forum/t/internal-flow-region-errors/100995>\
**Category:** CAD Mode Support\
**Created:** [April 23, 2026, 1:37pm UTC](https://www.simscale.com/forum/t/internal-flow-region-errors/100995 "2026-04-23T13:37:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![BrentVergeer](https://www.simscale.com/forum/letter_avatar/brentvergeer/32/5_5575768a8748004e209b776fc1b2916d.png) [@BrentVergeer](https://www.simscale.com/forum/u/BrentVergeer)\
**Post date:** [April 23, 2026, 1:37pm UTC](https://www.simscale.com/forum/t/internal-flow-region-errors/100995/1 "2026-04-23T13:37:07Z")

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Hi Simscale, I have been trying to give my “Cleanroom” simulation an internal flow region. Assigning the Seed and boundary faces to any of the model faces is not working.

What is the reason why these errors keep coming up and how do I fix this?

Thanks a lot

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**Author:** ![RicardoParis](https://www.simscale.com/forum/user_avatar/www.simscale.com/ricardoparis/32/30222_2.png) [@RicardoParis](https://www.simscale.com/forum/u/RicardoParis)\
**Post date:** [April 23, 2026, 3:19pm UTC](https://www.simscale.com/forum/t/internal-flow-region-errors/100995/3 "2026-04-23T15:19:48Z")

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[This document](https://www.simscale.com/knowledge-base/why-do-geometry-operations-fail/#:~:text=of%20the%20volumes%3A-,Figure%207,-%3A%20On%20the%20left) contains typical reasons for why flow region operations may fail. In your model I can find a bunch of edge-to-edge contacts, in particular between the floor and the side walls, that I would suggest that you fix.