Does SubDomain exist in fFEnicSx

General
1

What are the ways to define subdomains with fenicsx. For example, a circle centered at (x0,y0) with radius r. I tried to use the class SubDomain but it couldn’t be found. I’m using FEnicSx not fenics.

Thanks

2

See for instance Defining subdomains for different materials — FEniCSx tutorial

If you search the forum with the keyword meshtags you’ll find many other resources on this topic.

3

Thanks, I have already looked at that tutorial but does this SubDomain class still exist in FEnicSx? Because I tried to create a subdomain by creating a class inherited from SubDomain as in other tutorials but I couldn’t find how to import SubDomain. Maybe, creating subdomains by inheriting from SubDomain class is outdated in FEnicSx!? (I’m doing it in Python)

4

It does not exist anymore.

5

Allright. Thanks again.

6

For sub-domains in DOLFINx, we usually use functions based on numpy input-output and the function
dolfinx.mesh.locate_entities or dolfinx.mesh.locate_entities_boundary to determine what entities are in a subdomain, and in turn send the to a meshtag object to restrict integration.

Please provide a minimal reproducible example for more explicit feedback.

7

Thanks @dokken . I managed to create the subdomains using locate_entities. I wonder if using a subclassing strategy as in previous FEnics (class MySubdomain(SubDomain)) wouldn’t allow for a cleaner and more flexible way to define the subdomains because the encapsulation of other information necessary to create the subdomain in addition to the coordinates of points in the mesh. I watched a video on youtube (https://www.youtube.com/watch?v=D-YcVd4-_2E) where Garth Wells mention some design decisions related to using OOP. Looks like the decision was against using OOP for some things.

8

The interface of a “subdomain” class might look cleaner, but it results in less flexible code and less efficient code when used in python. The old sudomain class does nothing different than the locate_entities code, it just encapsulates multiple functions locate_entities and locate_entities_boundary for any dimension on an entity within a single function call.

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