# Coupling of two subdomains with new mixed-dimensional assembly

**URL:** <https://fenicsproject.discourse.group/t/coupling-of-two-subdomains-with-new-mixed-dimensional-assembly/16347>\
**Category:** dolfinx\
**Tags:** dolfinx\
**Created:** [November 20, 2024, 5:51pm UTC](https://fenicsproject.discourse.group/t/coupling-of-two-subdomains-with-new-mixed-dimensional-assembly/16347 "2024-11-20T17:51:58Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [November 20, 2024, 7:28pm UTC](https://fenicsproject.discourse.group/t/coupling-of-two-subdomains-with-new-mixed-dimensional-assembly/16347/2 "2024-11-20T19:28:13Z")

</div>

I would consider

> [@Discontinuity at interface using mixed domains](https://fenicsproject.discourse.group/t/discontinuity-at-interface-using-mixed-domains/15040):
>
> Hi all, Exactly like in [this topic](https://fenicsproject.discourse.group/t/imposing-a-discontinuity-at-interface-using-dg-method/11780/18) I am trying to impose a discontinuity at an interface between two subdomains. This time having two subdomains with only CG elements and coupling them with a dS term. @dokken published [this gist](https://gist.github.com/jorgensd/8a5c32f491195e838f5863ca88b27bce#file-problem-py) that I am trying to adapt in order to have: \frac{u(-)}{K(-)} = \frac{u(+)}{K(+)} \nabla u(-) - \nabla u(+) = 0 However I am struggling to adapt the interface terms to achieve the desired result. This is the DG formulation we had earlier: # Interface F += - dot…

and the demo I made in

> <https://gist.github.com/jorgensd/8a5c32f491195e838f5863ca88b27bce>

which couples two poisson problems discretised with different finite element spaces over a common boundary.

I have a similar implementation for RTC at

> <https://gist.github.com/jorgensd/befb28b02de55d254ffab6adcbc3261c>

---

_[View the full topic](https://fenicsproject.discourse.group/t/coupling-of-two-subdomains-with-new-mixed-dimensional-assembly/16347)._